example of research with rrl

• Affiliate Program

• UNITED STATES
• 台灣 (TAIWAN)
• TÜRKIYE (TURKEY)
• Academic Editing Services
• - Research Paper
• - Journal Manuscript
• - Dissertation
• - College & University Assignments
• Admissions Editing Services
• - Application Essay
• - Personal Statement
• - Recommendation Letter
• - Cover Letter
• - CV/Resume
• Business Editing Services
• - Business Documents
• - Report & Brochure
• - Website & Blog
• Writer Editing Services
• - Script & Screenplay
• Our Editors
• Client Reviews
• Editing & Proofreading Prices
• Wordvice Points
• Partner Discount
• Plagiarism Checker
• APA Citation Generator
• MLA Citation Generator
• Chicago Citation Generator
• Vancouver Citation Generator
• - APA Style
• - MLA Style
• - Chicago Style
• - Vancouver Style
• Writing & Editing Guide
• Academic Resources
• Admissions Resources

How to Make a Literature Review in Research (RRL Example)

What is an RRL in a research paper?

A relevant review of the literature (RRL) is an objective, concise, critical summary of published research literature relevant to a topic being researched in an article. In an RRL, you discuss knowledge and findings from existing literature relevant to your study topic. If there are conflicts or gaps in existing literature, you can also discuss these in your review, as well as how you will confront these missing elements or resolve these issues in your study.

To complete an RRL, you first need to collect relevant literature; this can include online and offline sources. Save all of your applicable resources as you will need to include them in your paper. When looking through these sources, take notes and identify concepts of each source to describe in the review of the literature.

A good RRL does NOT:

A literature review does not simply reference and list all of the material you have cited in your paper.

• Presenting material that is not directly relevant to your study will distract and frustrate the reader and make them lose sight of the purpose of your study.
• Starting a literature review with “A number of scholars have studied the relationship between X and Y” and simply listing who has studied the topic and what each scholar concluded is not going to strengthen your paper.

A good RRL DOES:

• Present a brief typology that orders articles and books into groups to help readers focus on unresolved debates, inconsistencies, tensions, and new questions about a research topic.
• Summarize the most relevant and important aspects of the scientific literature related to your area of research
• Synthesize what has been done in this area of research and by whom, highlight what previous research indicates about a topic, and identify potential gaps and areas of disagreement in the field
• Give the reader an understanding of the background of the field and show which studies are important—and highlight errors in previous studies

How long is a review of the literature for a research paper?

The length of a review of the literature depends on its purpose and target readership and can vary significantly in scope and depth. In a dissertation, thesis, or standalone review of literature, it is usually a full chapter of the text (at least 20 pages). Whereas, a standard research article or school assignment literature review section could only be a few paragraphs in the Introduction section .

Building Your Literature Review Bookshelf

One way to conceive of a literature review is to think about writing it as you would build a bookshelf. You don’t need to cut each piece by yourself from scratch. Rather, you can take the pieces that other researchers have cut out and put them together to build a framework on which to hang your own “books”—that is, your own study methods, results, and conclusions.

What Makes a Good Literature Review?

The contents of a literature review (RRL) are determined by many factors, including its precise purpose in the article, the degree of consensus with a given theory or tension between competing theories, the length of the article, the number of previous studies existing in the given field, etc. The following are some of the most important elements that a literature review provides.

Historical background for your research

Analyze what has been written about your field of research to highlight what is new and significant in your study—or how the analysis itself contributes to the understanding of this field, even in a small way. Providing a historical background also demonstrates to other researchers and journal editors your competency in discussing theoretical concepts. You should also make sure to understand how to paraphrase scientific literature to avoid plagiarism in your work.

The current context of your research

Discuss central (or peripheral) questions, issues, and debates in the field. Because a field is constantly being updated by new work, you can show where your research fits into this context and explain developments and trends in research.

A discussion of relevant theories and concepts

Theories and concepts should provide the foundation for your research. For example, if you are researching the relationship between ecological environments and human populations, provide models and theories that focus on specific aspects of this connection to contextualize your study. If your study asks a question concerning sustainability, mention a theory or model that underpins this concept. If it concerns invasive species, choose material that is focused in this direction.

Definitions of relevant terminology

In the natural sciences, the meaning of terms is relatively straightforward and consistent. But if you present a term that is obscure or context-specific, you should define the meaning of the term in the Introduction section (if you are introducing a study) or in the summary of the literature being reviewed.

Description of related relevant research

Include a description of related research that shows how your work expands or challenges earlier studies or fills in gaps in previous work. You can use your literature review as evidence of what works, what doesn’t, and what is missing in the field.

Supporting evidence for a practical problem or issue your research is addressing that demonstrates its importance: Referencing related research establishes your area of research as reputable and shows you are building upon previous work that other researchers have deemed significant.

Types of Literature Reviews

Literature reviews can differ in structure, length, amount, and breadth of content included. They can range from selective (a very narrow area of research or only a single work) to comprehensive (a larger amount or range of works). They can also be part of a larger work or stand on their own.

• A course assignment is an example of a selective, stand-alone work. It focuses on a small segment of the literature on a topic and makes up an entire work on its own.
• The literature review in a dissertation or thesis is both comprehensive and helps make up a larger work.
• A majority of journal articles start with a selective literature review to provide context for the research reported in the study; such a literature review is usually included in the Introduction section (but it can also follow the presentation of the results in the Discussion section ).
• Some literature reviews are both comprehensive and stand as a separate work—in this case, the entire article analyzes the literature on a given topic.

Literature Reviews Found in Academic Journals

The two types of literature reviews commonly found in journals are those introducing research articles (studies and surveys) and stand-alone literature analyses. They can differ in their scope, length, and specific purpose.

Literature reviews introducing research articles

The literature review found at the beginning of a journal article is used to introduce research related to the specific study and is found in the Introduction section, usually near the end. It is shorter than a stand-alone review because it must be limited to very specific studies and theories that are directly relevant to the current study. Its purpose is to set research precedence and provide support for the study’s theory, methods, results, and/or conclusions. Not all research articles contain an explicit review of the literature, but most do, whether it is a discrete section or indistinguishable from the rest of the Introduction.

How to structure a literature review for an article

When writing a literature review as part of an introduction to a study, simply follow the structure of the Introduction and move from the general to the specific—presenting the broadest background information about a topic first and then moving to specific studies that support your rationale , finally leading to your hypothesis statement. Such a literature review is often indistinguishable from the Introduction itself—the literature is INTRODUCING the background and defining the gaps your study aims to fill.

The stand-alone literature review

The literature review published as a stand-alone article presents and analyzes as many of the important publications in an area of study as possible to provide background information and context for a current area of research or a study. Stand-alone reviews are an excellent resource for researchers when they are first searching for the most relevant information on an area of study.

Such literature reviews are generally a bit broader in scope and can extend further back in time. This means that sometimes a scientific literature review can be highly theoretical, in addition to focusing on specific methods and outcomes of previous studies. In addition, all sections of such a “review article” refer to existing literature rather than describing the results of the authors’ own study.

In addition, this type of literature review is usually much longer than the literature review introducing a study. At the end of the review follows a conclusion that once again explicitly ties all of the cited works together to show how this analysis is itself a contribution to the literature. While not absolutely necessary, such articles often include the terms “Literature Review” or “Review of the Literature” in the title. Whether or not that is necessary or appropriate can also depend on the specific author instructions of the target journal. Have a look at this article for more input on how to compile a stand-alone review article that is insightful and helpful for other researchers in your field.

How to Write a Literature Review in 6 Steps

So how do authors turn a network of articles into a coherent review of relevant literature?

Writing a literature review is not usually a linear process—authors often go back and check the literature while reformulating their ideas or making adjustments to their study. Sometimes new findings are published before a study is completed and need to be incorporated into the current work. This also means you will not be writing the literature review at any one time, but constantly working on it before, during, and after your study is complete.

Here are some steps that will help you begin and follow through on your literature review.

Step 1: Choose a topic to write about—focus on and explore this topic.

Choose a topic that you are familiar with and highly interested in analyzing; a topic your intended readers and researchers will find interesting and useful; and a topic that is current, well-established in the field, and about which there has been sufficient research conducted for a review. This will help you find the “sweet spot” for what to focus on.

Step 2: Research and collect all the scholarly information on the topic that might be pertinent to your study.

This includes scholarly articles, books, conventions, conferences, dissertations, and theses—these and any other academic work related to your area of study is called “the literature.”

Step 3: Analyze the network of information that extends or responds to the major works in your area; select the material that is most useful.

Use thought maps and charts to identify intersections in the research and to outline important categories; select the material that will be most useful to your review.

Step 4: Describe and summarize each article—provide the essential information of the article that pertains to your study.

Determine 2-3 important concepts (depending on the length of your article) that are discussed in the literature; take notes about all of the important aspects of this study relevant to the topic being reviewed.

For example, in a given study, perhaps some of the main concepts are X, Y, and Z. Note these concepts and then write a brief summary about how the article incorporates them. In reviews that introduce a study, these can be relatively short. In stand-alone reviews, there may be significantly more texts and more concepts.

Step 5: Demonstrate how these concepts in the literature relate to what you discovered in your study or how the literature connects the concepts or topics being discussed.

In a literature review intro for an article, this information might include a summary of the results or methods of previous studies that correspond to and/or confirm those sections in your own study. For a stand-alone literature review, this may mean highlighting the concepts in each article and showing how they strengthen a hypothesis or show a pattern.

Discuss unaddressed issues in previous studies. These studies that are missing something you address are important to include in your literature review. In addition, those works whose theories and conclusions directly support your findings will be valuable to review here.

Step 6: Identify relationships in the literature and develop and connect your own ideas to them.

This is essentially the same as step 5 but focused on the connections between the literature and the current study or guiding concepts or arguments of the paper, not only on the connections between the works themselves.

Your hypothesis, argument, or guiding concept is the “golden thread” that will ultimately tie the works together and provide readers with specific insights they didn’t have before reading your literature review. Make sure you know where to put the research question , hypothesis, or statement of the problem in your research paper so that you guide your readers logically and naturally from your introduction of earlier work and evidence to the conclusions you want them to draw from the bigger picture.

Your literature review will not only cover publications on your topics but will include your own ideas and contributions. By following these steps you will be telling the specific story that sets the background and shows the significance of your research and you can turn a network of related works into a focused review of the literature.

Literature Review (RRL) Examples

Because creating sample literature reviews would take too long and not properly capture the nuances and detailed information needed for a good review, we have included some links to different types of literature reviews below. You can find links to more literature reviews in these categories by visiting the TUS Library’s website . Sample literature reviews as part of an article, dissertation, or thesis:

• Critical Thinking and Transferability: A Review of the Literature (Gwendolyn Reece)
• Building Customer Loyalty: A Customer Experience Based Approach in a Tourism Context (Martina Donnelly)

Sample stand-alone literature reviews

• Literature Review on Attitudes towards Disability (National Disability Authority)
• The Effects of Communication Styles on Marital Satisfaction (Hannah Yager)

Additional Literature Review Format Guidelines

In addition to the content guidelines above, authors also need to check which style guidelines to use ( APA , Chicago, MLA, etc.) and what specific rules the target journal might have for how to structure such articles or how many studies to include—such information can usually be found on the journals’ “Guide for Authors” pages. Additionally, use one of the four Wordvice citation generators below, choosing the citation style needed for your paper:

Wordvice Writing and Academic Editing Resources

Finally, after you have finished drafting your literature review, be sure to receive professional proofreading services , including paper editing for your academic work. A competent proofreader who understands academic writing conventions and the specific style guides used by academic journals will ensure that your paper is ready for publication in your target journal.

See our academic resources for further advice on references in your paper , how to write an abstract , how to write a research paper title, how to impress the editor of your target journal with a perfect cover letter , and dozens of other research writing and publication topics.

Review of Related Literature: Format, Example, & How to Make RRL

A review of related literature is a separate paper or a part of an article that collects and synthesizes discussion on a topic. Its purpose is to show the current state of research on the issue and highlight gaps in existing knowledge. A literature review can be included in a research paper or scholarly article, typically following the introduction and before the research methods section.

This article will clarify the definition, significance, and structure of a review of related literature. You’ll also learn how to organize your literature review and discover ideas for an RRL in different subjects.

🔤 What Is RRL?

• ❗ Significance of Literature Review
• 🔎 How to Search for Literature
• 🧩 Literature Review Structure
• 📋 Format of RRL — APA, MLA, & Others
• ✍️ How to Write an RRL
• 📚 Examples of RRL

🔗 References

A review of related literature (RRL) is a part of the research report that examines significant studies, theories, and concepts published in scholarly sources on a particular topic. An RRL includes 3 main components:

• A short overview and critique of the previous research.
• Similarities and differences between past studies and the current one.
• An explanation of the theoretical frameworks underpinning the research.

❗ Significance of Review of Related Literature

Although the goal of a review of related literature differs depending on the discipline and its intended use, its significance cannot be overstated. Here are some examples of how a review might be beneficial:

• It helps determine knowledge gaps .
• It saves from duplicating research that has already been conducted.
• It provides an overview of various research areas within the discipline.
• It demonstrates the researcher’s familiarity with the topic.

🔎 How to Perform a Literature Search

Including a description of your search strategy in the literature review section can significantly increase your grade. You can search sources with the following steps:

🧩 Literature Review Structure Example

The majority of literature reviews follow a standard introduction-body-conclusion structure. Let’s look at the RRL structure in detail.

Introduction of Review of Related Literature: Sample

An introduction should clarify the study topic and the depth of the information to be delivered. It should also explain the types of sources used. If your lit. review is part of a larger research proposal or project, you can combine its introductory paragraph with the introduction of your paper.

Here is a sample introduction to an RRL about cyberbullying:

Bullying has troubled people since the beginning of time. However, with modern technological advancements, especially social media, bullying has evolved into cyberbullying. As a result, nowadays, teenagers and adults cannot flee their bullies, which makes them feel lonely and helpless. This literature review will examine recent studies on cyberbullying.

Sample Review of Related Literature Thesis

A thesis statement should include the central idea of your literature review and the primary supporting elements you discovered in the literature. Thesis statements are typically put at the end of the introductory paragraph.

Look at a sample thesis of a review of related literature:

This literature review shows that scholars have recently covered the issues of bullies’ motivation, the impact of bullying on victims and aggressors, common cyberbullying techniques, and victims’ coping strategies. However, there is still no agreement on the best practices to address cyberbullying.

Literature Review Body Paragraph Example

The main body of a literature review should provide an overview of the existing research on the issue. Body paragraphs should not just summarize each source but analyze them. You can organize your paragraphs with these 3 elements:

• Claim . Start with a topic sentence linked to your literature review purpose.
• Evidence . Cite relevant information from your chosen sources.
• Discussion . Explain how the cited data supports your claim.

Here’s a literature review body paragraph example:

Scholars have examined the link between the aggressor and the victim. Beran et al. (2007) state that students bullied online often become cyberbullies themselves. Faucher et al. (2014) confirm this with their findings: they discovered that male and female students began engaging in cyberbullying after being subject to bullying. Hence, one can conclude that being a victim of bullying increases one’s likelihood of becoming a cyberbully.

Review of Related Literature: Conclusion

A conclusion presents a general consensus on the topic. Depending on your literature review purpose, it might include the following:

• Introduction to further research . If you write a literature review as part of a larger research project, you can present your research question in your conclusion .
• Overview of theories . You can summarize critical theories and concepts to help your reader understand the topic better.
• Discussion of the gap . If you identified a research gap in the reviewed literature, your conclusion could explain why that gap is significant.

Check out a conclusion example that discusses a research gap:

There is extensive research into bullies’ motivation, the consequences of bullying for victims and aggressors, strategies for bullying, and coping with it. Yet, scholars still have not reached a consensus on what to consider the best practices to combat cyberbullying. This question is of great importance because of the significant adverse effects of cyberbullying on victims and bullies.

📋 Format of RRL — APA, MLA, & Others

In this section, we will discuss how to format an RRL according to the most common citation styles: APA, Chicago, MLA, and Harvard.

Writing a literature review using the APA7 style requires the following text formatting:

• When using APA in-text citations , include the author’s last name and the year of publication in parentheses.
• For direct quotations , you must also add the page number. If you use sources without page numbers, such as websites or e-books, include a paragraph number instead.
• When referring to the author’s name in a sentence , you do not need to repeat it at the end of the sentence. Instead, include the year of publication inside the parentheses after their name.
• The reference list should be included at the end of your literature review. It is always alphabetized by the last name of the author (from A to Z), and the lines are indented one-half inch from the left margin of your paper. Do not forget to invert authors’ names (the last name should come first) and include the full titles of journals instead of their abbreviations. If you use an online source, add its URL.

The RRL format in the Chicago style is as follows:

• Author-date . You place your citations in brackets within the text, indicating the name of the author and the year of publication.
• Notes and bibliography . You place your citations in numbered footnotes or endnotes to connect the citation back to the source in the bibliography.
• The reference list, or bibliography , in Chicago style, is at the end of a literature review. The sources are arranged alphabetically and single-spaced. Each bibliography entry begins with the author’s name and the source’s title, followed by publication information, such as the city of publication, the publisher, and the year of publication.

Writing a literature review using the MLA style requires the following text formatting:

• In the MLA format, you can cite a source in the text by indicating the author’s last name and the page number in parentheses at the end of the citation. If the cited information takes several pages, you need to include all the page numbers.
• The reference list in MLA style is titled “ Works Cited .” In this section, all sources used in the paper should be listed in alphabetical order. Each entry should contain the author, title of the source, title of the journal or a larger volume, other contributors, version, number, publisher, and publication date.

The Harvard style requires you to use the following text formatting for your RRL:

• In-text citations in the Harvard style include the author’s last name and the year of publication. If you are using a direct quote in your literature review, you need to add the page number as well.
• Arrange your list of references alphabetically. Each entry should contain the author’s last name, their initials, the year of publication, the title of the source, and other publication information, like the journal title and issue number or the publisher.

✍️ How to Write Review of Related Literature – Sample

Literature reviews can be organized in many ways depending on what you want to achieve with them. In this section, we will look at 3 examples of how you can write your RRL.

Thematic Literature Review

A thematic literature review is arranged around central themes or issues discussed in the sources. If you have identified some recurring themes in the literature, you can divide your RRL into sections that address various aspects of the topic. For example, if you examine studies on e-learning, you can distinguish such themes as the cost-effectiveness of online learning, the technologies used, and its effectiveness compared to traditional education.

Chronological Literature Review

A chronological literature review is a way to track the development of the topic over time. If you use this method, avoid merely listing and summarizing sources in chronological order. Instead, try to analyze the trends, turning moments, and critical debates that have shaped the field’s path. Also, you can give your interpretation of how and why specific advances occurred.

Methodological Literature Review

A methodological literature review differs from the preceding ones in that it usually doesn’t focus on the sources’ content. Instead, it is concerned with the research methods . So, if your references come from several disciplines or fields employing various research techniques, you can compare the findings and conclusions of different methodologies, for instance:

• empirical vs. theoretical studies;
• qualitative vs. quantitative research.

📚 Examples of Review of Related Literature and Studies

We have prepared a short example of RRL on climate change for you to see how everything works in practice!

Climate change is one of the most important issues nowadays. Based on a variety of facts, it is now clearer than ever that humans are altering the Earth's climate. The atmosphere and oceans have warmed, causing sea level rise, a significant loss of Arctic ice, and other climate-related changes. This literature review provides a thorough summary of research on climate change, focusing on climate change fingerprints and evidence of human influence on the Earth's climate system.

Physical Mechanisms and Evidence of Human Influence

Scientists are convinced that climate change is directly influenced by the emission of greenhouse gases. They have carefully analyzed various climate data and evidence, concluding that the majority of the observed global warming over the past 50 years cannot be explained by natural factors alone. Instead, there is compelling evidence pointing to a significant contribution of human activities, primarily the emission of greenhouse gases (Walker, 2014). For example, based on simple physics calculations, doubled carbon dioxide concentration in the atmosphere can lead to a global temperature increase of approximately 1 degree Celsius. (Elderfield, 2022). In order to determine the human influence on climate, scientists still have to analyze a lot of natural changes that affect temperature, precipitation, and other components of climate on timeframes ranging from days to decades and beyond.

Fingerprinting Climate Change

Fingerprinting climate change is a useful tool to identify the causes of global warming because different factors leave unique marks on climate records. This is evident when scientists look beyond overall temperature changes and examine how warming is distributed geographically and over time (Watson, 2022). By investigating these climate patterns, scientists can obtain a more complex understanding of the connections between natural climate variability and climate variability caused by human activity.

Modeling Climate Change and Feedback

To accurately predict the consequences of feedback mechanisms, the rate of warming, and regional climate change, scientists can employ sophisticated mathematical models of the atmosphere, ocean, land, and ice (the cryosphere). These models are grounded in well-established physical laws and incorporate the latest scientific understanding of climate-related processes (Shuckburgh, 2013). Although different climate models produce slightly varying projections for future warming, they all will agree that feedback mechanisms play a significant role in amplifying the initial warming caused by greenhouse gas emissions. (Meehl, 2019).

In conclusion, the literature on global warming indicates that there are well-understood physical processes that link variations in greenhouse gas concentrations to climate change. In addition, it covers the scientific proof that the rates of these gases in the atmosphere have increased and continue to rise fast. According to the sources, the majority of this recent change is almost definitely caused by greenhouse gas emissions produced by human activities. Citizens and governments can alter their energy production methods and consumption patterns to reduce greenhouse gas emissions and, thus, the magnitude of climate change. By acting now, society can prevent the worst consequences of climate change and build a more resilient and sustainable future for generations to come.

Have you ever struggled with finding the topic for an RRL in different subjects? Read the following paragraphs to get some ideas!

Nursing Literature Review Example

Many topics in the nursing field require research. For example, you can write a review of literature related to dengue fever . Give a general overview of dengue virus infections, including its clinical symptoms, diagnosis, prevention, and therapy.

Another good idea is to review related literature and studies about teenage pregnancy . This review can describe the effectiveness of specific programs for adolescent mothers and their children and summarize recommendations for preventing early pregnancy.

📝 Check out some more valuable examples below:

• Hospital Readmissions: Literature Review .
• Literature Review: Lower Sepsis Mortality Rates .
• Breast Cancer: Literature Review .
• Sexually Transmitted Diseases: Literature Review .
• PICO for Pressure Ulcers: Literature Review .
• COVID-19 Spread Prevention: Literature Review .
• Chronic Obstructive Pulmonary Disease: Literature Review .
• Hypertension Treatment Adherence: Literature Review .
• Neonatal Sepsis Prevention: Literature Review .
• Healthcare-Associated Infections: Literature Review .
• Understaffing in Nursing: Literature Review .

Psychology Literature Review Example

If you look for an RRL topic in psychology , you can write a review of related literature about stress . Summarize scientific evidence about stress stages, side effects, types, or reduction strategies. Or you can write a review of related literature about computer game addiction . In this case, you may concentrate on the neural mechanisms underlying the internet gaming disorder, compare it to other addictions, or evaluate treatment strategies.

A review of related literature about cyberbullying is another interesting option. You can highlight the impact of cyberbullying on undergraduate students’ academic, social, and emotional development.

📝 Look at the examples that we have prepared for you to come up with some more ideas:

• Mindfulness in Counseling: A Literature Review .
• Team-Building Across Cultures: Literature Review .
• Anxiety and Decision Making: Literature Review .
• Literature Review on Depression .
• Literature Review on Narcissism .
• Effects of Depression Among Adolescents .
• Causes and Effects of Anxiety in Children .

Literature Review — Sociology Example

Sociological research poses critical questions about social structures and phenomena. For example, you can write a review of related literature about child labor , exploring cultural beliefs and social norms that normalize the exploitation of children. Or you can create a review of related literature about social media . It can investigate the impact of social media on relationships between adolescents or the role of social networks on immigrants’ acculturation .

📝 You can find some more ideas below!

• Single Mothers’ Experiences of Relationships with Their Adolescent Sons .
• Teachers and Students’ Gender-Based Interactions .
• Gender Identity: Biological Perspective and Social Cognitive Theory .
• Gender: Culturally-Prescribed Role or Biological Sex .
• The Influence of Opioid Misuse on Academic Achievement of Veteran Students .
• The Importance of Ethics in Research .
• The Role of Family and Social Network Support in Mental Health .

Education Literature Review Example

For your education studies , you can write a review of related literature about academic performance to determine factors that affect student achievement and highlight research gaps. One more idea is to create a review of related literature on study habits , considering their role in the student’s life and academic outcomes.

You can also evaluate a computerized grading system in a review of related literature to single out its advantages and barriers to implementation. Or you can complete a review of related literature on instructional materials to identify their most common types and effects on student achievement.

📝 Find some inspiration in the examples below:

• Literature Review on Online Learning Challenges From COVID-19 .
• Education, Leadership, and Management: Literature Review .
• Literature Review: Standardized Testing Bias .
• Bullying of Disabled Children in School .
• Interventions and Letter & Sound Recognition: A Literature Review .
• Social-Emotional Skills Program for Preschoolers .
• Effectiveness of Educational Leadership Management Skills .

Business Research Literature Review

If you’re a business student, you can focus on customer satisfaction in your review of related literature. Discuss specific customer satisfaction features and how it is affected by service quality and prices. You can also create a theoretical literature review about consumer buying behavior to evaluate theories that have significantly contributed to understanding how consumers make purchasing decisions.

📝 Look at the examples to get more exciting ideas:

• Leadership and Communication: Literature Review .
• Human Resource Development: Literature Review .
• Project Management. Literature Review .
• Strategic HRM: A Literature Review .
• Customer Relationship Management: Literature Review .
• Literature Review on International Financial Reporting Standards .
• Cultures of Management: Literature Review .

To conclude, a review of related literature is a significant genre of scholarly works that can be applied in various disciplines and for multiple goals. The sources examined in an RRL provide theoretical frameworks for future studies and help create original research questions and hypotheses.

When you finish your outstanding literature review, don’t forget to check whether it sounds logical and coherent. Our text-to-speech tool can help you with that!

• Literature Reviews | University of North Carolina at Chapel Hill
• Writing a Literature Review | Purdue Online Writing Lab
• Learn How to Write a Review of Literature | University of Wisconsin-Madison
• The Literature Review: A Few Tips on Conducting It | University of Toronto
• Writing a Literature Review | UC San Diego
• Conduct a Literature Review | The University of Arizona
• Methods for Literature Reviews | National Library of Medicine
• Literature Reviews: 5. Write the Review | Georgia State University

How to Write an Animal Testing Essay: Tips for Argumentative & Persuasive Papers

Descriptive essay topics: examples, outline, & more.

• UWF Libraries

Literature Review: Conducting & Writing

• Sample Literature Reviews
• Steps for Conducting a Lit Review
• Finding "The Literature"
• Organizing/Writing
• APA Style This link opens in a new window
• Chicago: Notes Bibliography This link opens in a new window
• MLA Style This link opens in a new window

Sample Lit Reviews from Communication Arts

Have an exemplary literature review.

• Literature Review Sample 1
• Literature Review Sample 2
• Literature Review Sample 3

Have you written a stellar literature review you care to share for teaching purposes?

Are you an instructor who has received an exemplary literature review and have permission from the student to post?

Please contact Britt McGowan at [email protected] for inclusion in this guide. All disciplines welcome and encouraged.

• << Previous: MLA Style
• Next: Get Help! >>
• Last Updated: Mar 22, 2024 9:37 AM
• URL: https://libguides.uwf.edu/litreview

Purdue Online Writing Lab Purdue OWL® College of Liberal Arts

Writing a Literature Review

Welcome to the Purdue OWL

This page is brought to you by the OWL at Purdue University. When printing this page, you must include the entire legal notice.

Copyright ©1995-2018 by The Writing Lab & The OWL at Purdue and Purdue University. All rights reserved. This material may not be published, reproduced, broadcast, rewritten, or redistributed without permission. Use of this site constitutes acceptance of our terms and conditions of fair use.

A literature review is a document or section of a document that collects key sources on a topic and discusses those sources in conversation with each other (also called synthesis ). The lit review is an important genre in many disciplines, not just literature (i.e., the study of works of literature such as novels and plays). When we say “literature review” or refer to “the literature,” we are talking about the research ( scholarship ) in a given field. You will often see the terms “the research,” “the scholarship,” and “the literature” used mostly interchangeably.

Where, when, and why would I write a lit review?

There are a number of different situations where you might write a literature review, each with slightly different expectations; different disciplines, too, have field-specific expectations for what a literature review is and does. For instance, in the humanities, authors might include more overt argumentation and interpretation of source material in their literature reviews, whereas in the sciences, authors are more likely to report study designs and results in their literature reviews; these differences reflect these disciplines’ purposes and conventions in scholarship. You should always look at examples from your own discipline and talk to professors or mentors in your field to be sure you understand your discipline’s conventions, for literature reviews as well as for any other genre.

A literature review can be a part of a research paper or scholarly article, usually falling after the introduction and before the research methods sections. In these cases, the lit review just needs to cover scholarship that is important to the issue you are writing about; sometimes it will also cover key sources that informed your research methodology.

Lit reviews can also be standalone pieces, either as assignments in a class or as publications. In a class, a lit review may be assigned to help students familiarize themselves with a topic and with scholarship in their field, get an idea of the other researchers working on the topic they’re interested in, find gaps in existing research in order to propose new projects, and/or develop a theoretical framework and methodology for later research. As a publication, a lit review usually is meant to help make other scholars’ lives easier by collecting and summarizing, synthesizing, and analyzing existing research on a topic. This can be especially helpful for students or scholars getting into a new research area, or for directing an entire community of scholars toward questions that have not yet been answered.

What are the parts of a lit review?

Most lit reviews use a basic introduction-body-conclusion structure; if your lit review is part of a larger paper, the introduction and conclusion pieces may be just a few sentences while you focus most of your attention on the body. If your lit review is a standalone piece, the introduction and conclusion take up more space and give you a place to discuss your goals, research methods, and conclusions separately from where you discuss the literature itself.

Introduction:

• An introductory paragraph that explains what your working topic and thesis is
• A forecast of key topics or texts that will appear in the review
• Potentially, a description of how you found sources and how you analyzed them for inclusion and discussion in the review (more often found in published, standalone literature reviews than in lit review sections in an article or research paper)
• Summarize and synthesize: Give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: Don’t just paraphrase other researchers – add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically Evaluate: Mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: Use transition words and topic sentence to draw connections, comparisons, and contrasts.

Conclusion:

• Summarize the key findings you have taken from the literature and emphasize their significance
• Connect it back to your primary research question

How should I organize my lit review?

Lit reviews can take many different organizational patterns depending on what you are trying to accomplish with the review. Here are some examples:

• Chronological : The simplest approach is to trace the development of the topic over time, which helps familiarize the audience with the topic (for instance if you are introducing something that is not commonly known in your field). If you choose this strategy, be careful to avoid simply listing and summarizing sources in order. Try to analyze the patterns, turning points, and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred (as mentioned previously, this may not be appropriate in your discipline — check with a teacher or mentor if you’re unsure).
• Thematic : If you have found some recurring central themes that you will continue working with throughout your piece, you can organize your literature review into subsections that address different aspects of the topic. For example, if you are reviewing literature about women and religion, key themes can include the role of women in churches and the religious attitude towards women.
• Qualitative versus quantitative research
• Empirical versus theoretical scholarship
• Divide the research by sociological, historical, or cultural sources
• Theoretical : In many humanities articles, the literature review is the foundation for the theoretical framework. You can use it to discuss various theories, models, and definitions of key concepts. You can argue for the relevance of a specific theoretical approach or combine various theorical concepts to create a framework for your research.

What are some strategies or tips I can use while writing my lit review?

Any lit review is only as good as the research it discusses; make sure your sources are well-chosen and your research is thorough. Don’t be afraid to do more research if you discover a new thread as you’re writing. More info on the research process is available in our "Conducting Research" resources .

As you’re doing your research, create an annotated bibliography ( see our page on the this type of document ). Much of the information used in an annotated bibliography can be used also in a literature review, so you’ll be not only partially drafting your lit review as you research, but also developing your sense of the larger conversation going on among scholars, professionals, and any other stakeholders in your topic.

Usually you will need to synthesize research rather than just summarizing it. This means drawing connections between sources to create a picture of the scholarly conversation on a topic over time. Many student writers struggle to synthesize because they feel they don’t have anything to add to the scholars they are citing; here are some strategies to help you:

• It often helps to remember that the point of these kinds of syntheses is to show your readers how you understand your research, to help them read the rest of your paper.
• Writing teachers often say synthesis is like hosting a dinner party: imagine all your sources are together in a room, discussing your topic. What are they saying to each other?
• Look at the in-text citations in each paragraph. Are you citing just one source for each paragraph? This usually indicates summary only. When you have multiple sources cited in a paragraph, you are more likely to be synthesizing them (not always, but often
• Read more about synthesis here.

The most interesting literature reviews are often written as arguments (again, as mentioned at the beginning of the page, this is discipline-specific and doesn’t work for all situations). Often, the literature review is where you can establish your research as filling a particular gap or as relevant in a particular way. You have some chance to do this in your introduction in an article, but the literature review section gives a more extended opportunity to establish the conversation in the way you would like your readers to see it. You can choose the intellectual lineage you would like to be part of and whose definitions matter most to your thinking (mostly humanities-specific, but this goes for sciences as well). In addressing these points, you argue for your place in the conversation, which tends to make the lit review more compelling than a simple reporting of other sources.

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• PLoS Comput Biol
• v.9(7); 2013 Jul

Ten Simple Rules for Writing a Literature Review

Marco pautasso.

1 Centre for Functional and Evolutionary Ecology (CEFE), CNRS, Montpellier, France

2 Centre for Biodiversity Synthesis and Analysis (CESAB), FRB, Aix-en-Provence, France

Literature reviews are in great demand in most scientific fields. Their need stems from the ever-increasing output of scientific publications [1] . For example, compared to 1991, in 2008 three, eight, and forty times more papers were indexed in Web of Science on malaria, obesity, and biodiversity, respectively [2] . Given such mountains of papers, scientists cannot be expected to examine in detail every single new paper relevant to their interests [3] . Thus, it is both advantageous and necessary to rely on regular summaries of the recent literature. Although recognition for scientists mainly comes from primary research, timely literature reviews can lead to new synthetic insights and are often widely read [4] . For such summaries to be useful, however, they need to be compiled in a professional way [5] .

When starting from scratch, reviewing the literature can require a titanic amount of work. That is why researchers who have spent their career working on a certain research issue are in a perfect position to review that literature. Some graduate schools are now offering courses in reviewing the literature, given that most research students start their project by producing an overview of what has already been done on their research issue [6] . However, it is likely that most scientists have not thought in detail about how to approach and carry out a literature review.

Reviewing the literature requires the ability to juggle multiple tasks, from finding and evaluating relevant material to synthesising information from various sources, from critical thinking to paraphrasing, evaluating, and citation skills [7] . In this contribution, I share ten simple rules I learned working on about 25 literature reviews as a PhD and postdoctoral student. Ideas and insights also come from discussions with coauthors and colleagues, as well as feedback from reviewers and editors.

Rule 1: Define a Topic and Audience

How to choose which topic to review? There are so many issues in contemporary science that you could spend a lifetime of attending conferences and reading the literature just pondering what to review. On the one hand, if you take several years to choose, several other people may have had the same idea in the meantime. On the other hand, only a well-considered topic is likely to lead to a brilliant literature review [8] . The topic must at least be:

• interesting to you (ideally, you should have come across a series of recent papers related to your line of work that call for a critical summary),
• an important aspect of the field (so that many readers will be interested in the review and there will be enough material to write it), and
• a well-defined issue (otherwise you could potentially include thousands of publications, which would make the review unhelpful).

Ideas for potential reviews may come from papers providing lists of key research questions to be answered [9] , but also from serendipitous moments during desultory reading and discussions. In addition to choosing your topic, you should also select a target audience. In many cases, the topic (e.g., web services in computational biology) will automatically define an audience (e.g., computational biologists), but that same topic may also be of interest to neighbouring fields (e.g., computer science, biology, etc.).

Rule 2: Search and Re-search the Literature

After having chosen your topic and audience, start by checking the literature and downloading relevant papers. Five pieces of advice here:

• keep track of the search items you use (so that your search can be replicated [10] ),
• keep a list of papers whose pdfs you cannot access immediately (so as to retrieve them later with alternative strategies),
• use a paper management system (e.g., Mendeley, Papers, Qiqqa, Sente),
• define early in the process some criteria for exclusion of irrelevant papers (these criteria can then be described in the review to help define its scope), and
• do not just look for research papers in the area you wish to review, but also seek previous reviews.

The chances are high that someone will already have published a literature review ( Figure 1 ), if not exactly on the issue you are planning to tackle, at least on a related topic. If there are already a few or several reviews of the literature on your issue, my advice is not to give up, but to carry on with your own literature review,

The bottom-right situation (many literature reviews but few research papers) is not just a theoretical situation; it applies, for example, to the study of the impacts of climate change on plant diseases, where there appear to be more literature reviews than research studies [33] .

• discussing in your review the approaches, limitations, and conclusions of past reviews,
• trying to find a new angle that has not been covered adequately in the previous reviews, and
• incorporating new material that has inevitably accumulated since their appearance.

When searching the literature for pertinent papers and reviews, the usual rules apply:

• be thorough,
• use different keywords and database sources (e.g., DBLP, Google Scholar, ISI Proceedings, JSTOR Search, Medline, Scopus, Web of Science), and
• look at who has cited past relevant papers and book chapters.

Rule 3: Take Notes While Reading

If you read the papers first, and only afterwards start writing the review, you will need a very good memory to remember who wrote what, and what your impressions and associations were while reading each single paper. My advice is, while reading, to start writing down interesting pieces of information, insights about how to organize the review, and thoughts on what to write. This way, by the time you have read the literature you selected, you will already have a rough draft of the review.

Of course, this draft will still need much rewriting, restructuring, and rethinking to obtain a text with a coherent argument [11] , but you will have avoided the danger posed by staring at a blank document. Be careful when taking notes to use quotation marks if you are provisionally copying verbatim from the literature. It is advisable then to reformulate such quotes with your own words in the final draft. It is important to be careful in noting the references already at this stage, so as to avoid misattributions. Using referencing software from the very beginning of your endeavour will save you time.

Rule 4: Choose the Type of Review You Wish to Write

After having taken notes while reading the literature, you will have a rough idea of the amount of material available for the review. This is probably a good time to decide whether to go for a mini- or a full review. Some journals are now favouring the publication of rather short reviews focusing on the last few years, with a limit on the number of words and citations. A mini-review is not necessarily a minor review: it may well attract more attention from busy readers, although it will inevitably simplify some issues and leave out some relevant material due to space limitations. A full review will have the advantage of more freedom to cover in detail the complexities of a particular scientific development, but may then be left in the pile of the very important papers “to be read” by readers with little time to spare for major monographs.

There is probably a continuum between mini- and full reviews. The same point applies to the dichotomy of descriptive vs. integrative reviews. While descriptive reviews focus on the methodology, findings, and interpretation of each reviewed study, integrative reviews attempt to find common ideas and concepts from the reviewed material [12] . A similar distinction exists between narrative and systematic reviews: while narrative reviews are qualitative, systematic reviews attempt to test a hypothesis based on the published evidence, which is gathered using a predefined protocol to reduce bias [13] , [14] . When systematic reviews analyse quantitative results in a quantitative way, they become meta-analyses. The choice between different review types will have to be made on a case-by-case basis, depending not just on the nature of the material found and the preferences of the target journal(s), but also on the time available to write the review and the number of coauthors [15] .

Rule 5: Keep the Review Focused, but Make It of Broad Interest

Whether your plan is to write a mini- or a full review, it is good advice to keep it focused 16 , 17 . Including material just for the sake of it can easily lead to reviews that are trying to do too many things at once. The need to keep a review focused can be problematic for interdisciplinary reviews, where the aim is to bridge the gap between fields [18] . If you are writing a review on, for example, how epidemiological approaches are used in modelling the spread of ideas, you may be inclined to include material from both parent fields, epidemiology and the study of cultural diffusion. This may be necessary to some extent, but in this case a focused review would only deal in detail with those studies at the interface between epidemiology and the spread of ideas.

While focus is an important feature of a successful review, this requirement has to be balanced with the need to make the review relevant to a broad audience. This square may be circled by discussing the wider implications of the reviewed topic for other disciplines.

Rule 6: Be Critical and Consistent

Reviewing the literature is not stamp collecting. A good review does not just summarize the literature, but discusses it critically, identifies methodological problems, and points out research gaps [19] . After having read a review of the literature, a reader should have a rough idea of:

• the major achievements in the reviewed field,
• the main areas of debate, and
• the outstanding research questions.

It is challenging to achieve a successful review on all these fronts. A solution can be to involve a set of complementary coauthors: some people are excellent at mapping what has been achieved, some others are very good at identifying dark clouds on the horizon, and some have instead a knack at predicting where solutions are going to come from. If your journal club has exactly this sort of team, then you should definitely write a review of the literature! In addition to critical thinking, a literature review needs consistency, for example in the choice of passive vs. active voice and present vs. past tense.

Rule 7: Find a Logical Structure

Like a well-baked cake, a good review has a number of telling features: it is worth the reader's time, timely, systematic, well written, focused, and critical. It also needs a good structure. With reviews, the usual subdivision of research papers into introduction, methods, results, and discussion does not work or is rarely used. However, a general introduction of the context and, toward the end, a recapitulation of the main points covered and take-home messages make sense also in the case of reviews. For systematic reviews, there is a trend towards including information about how the literature was searched (database, keywords, time limits) [20] .

How can you organize the flow of the main body of the review so that the reader will be drawn into and guided through it? It is generally helpful to draw a conceptual scheme of the review, e.g., with mind-mapping techniques. Such diagrams can help recognize a logical way to order and link the various sections of a review [21] . This is the case not just at the writing stage, but also for readers if the diagram is included in the review as a figure. A careful selection of diagrams and figures relevant to the reviewed topic can be very helpful to structure the text too [22] .

Rule 8: Make Use of Feedback

Reviews of the literature are normally peer-reviewed in the same way as research papers, and rightly so [23] . As a rule, incorporating feedback from reviewers greatly helps improve a review draft. Having read the review with a fresh mind, reviewers may spot inaccuracies, inconsistencies, and ambiguities that had not been noticed by the writers due to rereading the typescript too many times. It is however advisable to reread the draft one more time before submission, as a last-minute correction of typos, leaps, and muddled sentences may enable the reviewers to focus on providing advice on the content rather than the form.

Feedback is vital to writing a good review, and should be sought from a variety of colleagues, so as to obtain a diversity of views on the draft. This may lead in some cases to conflicting views on the merits of the paper, and on how to improve it, but such a situation is better than the absence of feedback. A diversity of feedback perspectives on a literature review can help identify where the consensus view stands in the landscape of the current scientific understanding of an issue [24] .

Rule 9: Include Your Own Relevant Research, but Be Objective

In many cases, reviewers of the literature will have published studies relevant to the review they are writing. This could create a conflict of interest: how can reviewers report objectively on their own work [25] ? Some scientists may be overly enthusiastic about what they have published, and thus risk giving too much importance to their own findings in the review. However, bias could also occur in the other direction: some scientists may be unduly dismissive of their own achievements, so that they will tend to downplay their contribution (if any) to a field when reviewing it.

In general, a review of the literature should neither be a public relations brochure nor an exercise in competitive self-denial. If a reviewer is up to the job of producing a well-organized and methodical review, which flows well and provides a service to the readership, then it should be possible to be objective in reviewing one's own relevant findings. In reviews written by multiple authors, this may be achieved by assigning the review of the results of a coauthor to different coauthors.

Rule 10: Be Up-to-Date, but Do Not Forget Older Studies

Given the progressive acceleration in the publication of scientific papers, today's reviews of the literature need awareness not just of the overall direction and achievements of a field of inquiry, but also of the latest studies, so as not to become out-of-date before they have been published. Ideally, a literature review should not identify as a major research gap an issue that has just been addressed in a series of papers in press (the same applies, of course, to older, overlooked studies (“sleeping beauties” [26] )). This implies that literature reviewers would do well to keep an eye on electronic lists of papers in press, given that it can take months before these appear in scientific databases. Some reviews declare that they have scanned the literature up to a certain point in time, but given that peer review can be a rather lengthy process, a full search for newly appeared literature at the revision stage may be worthwhile. Assessing the contribution of papers that have just appeared is particularly challenging, because there is little perspective with which to gauge their significance and impact on further research and society.

Inevitably, new papers on the reviewed topic (including independently written literature reviews) will appear from all quarters after the review has been published, so that there may soon be the need for an updated review. But this is the nature of science [27] – [32] . I wish everybody good luck with writing a review of the literature.

Acknowledgments

Many thanks to M. Barbosa, K. Dehnen-Schmutz, T. Döring, D. Fontaneto, M. Garbelotto, O. Holdenrieder, M. Jeger, D. Lonsdale, A. MacLeod, P. Mills, M. Moslonka-Lefebvre, G. Stancanelli, P. Weisberg, and X. Xu for insights and discussions, and to P. Bourne, T. Matoni, and D. Smith for helpful comments on a previous draft.

Funding Statement

This work was funded by the French Foundation for Research on Biodiversity (FRB) through its Centre for Synthesis and Analysis of Biodiversity data (CESAB), as part of the NETSEED research project. The funders had no role in the preparation of the manuscript.

The Sheridan Libraries

• Write a Literature Review
• Sheridan Libraries
• Find This link opens in a new window
• Evaluate This link opens in a new window

Get Organized

• Lit Review Prep Use this template to help you evaluate your sources, create article summaries for an annotated bibliography, and a synthesis matrix for your lit review outline.

Synthesize your Information

Synthesize: combine separate elements to form a whole.

Synthesis Matrix

A synthesis matrix helps you record the main points of each source and document how sources relate to each other.

After summarizing and evaluating your sources, arrange them in a matrix or use a citation manager to help you see how they relate to each other and apply to each of your themes or variables.  

By arranging your sources by theme or variable, you can see how your sources relate to each other, and can start thinking about how you weave them together to create a narrative.

• Step-by-Step Approach
• Example Matrix from NSCU
• Matrix Template
• << Previous: Summarize
• Next: Integrate >>
• Last Updated: Sep 26, 2023 10:25 AM
• URL: https://guides.library.jhu.edu/lit-review

• University of Oregon Libraries
• Research Guides

How to Write a Literature Review

• 6. Synthesize
• Literature Reviews: A Recap
• Reading Journal Articles
• Does it Describe a Literature Review?
• 1. Identify the Question
• 2. Review Discipline Styles
• Searching Article Databases
• Finding Full-Text of an Article
• Citation Chaining
• When to Stop Searching
• 4. Manage Your References
• 5. Critically Analyze and Evaluate

Synthesis Visualization

Synthesis matrix example.

• 7. Write a Literature Review

• Synthesis Worksheet

About Synthesis

Approaches to synthesis.

You can sort the literature in various ways, for example:

How to Begin?

Read your sources carefully and find the main idea(s) of each source

Look for similarities in your sources – which sources are talking about the same main ideas? (for example, sources that discuss the historical background on your topic)

Use the worksheet (above) or synthesis matrix (below) to get organized

This work can be messy. Don't worry if you have to go through a few iterations of the worksheet or matrix as you work on your lit review!

Four Examples of Student Writing

In the four examples below, only ONE shows a good example of synthesis: the fourth column, or  Student D . For a web accessible version, click the link below the image.

Long description of "Four Examples of Student Writing" for web accessibility

• Download a copy of the "Four Examples of Student Writing" chart

Click on the example to view the pdf.

From Jennifer Lim

• << Previous: 5. Critically Analyze and Evaluate
• Next: 7. Write a Literature Review >>
• Last Updated: Jan 10, 2024 4:46 PM
• URL: https://researchguides.uoregon.edu/litreview

Contact Us Library Accessibility UO Libraries Privacy Notices and Procedures

1501 Kincaid Street Eugene, OR 97403 P: 541-346-3053 F: 541-346-3485

• Visit us on Facebook
• Visit us on Twitter
• Visit us on Youtube
• Visit us on Instagram
• Report a Concern
• Nondiscrimination and Title IX
• Accessibility
• Privacy Policy
• Find People

What is RRL in Research

Table of Contents

Have you ever felt lost in a sea of information while doing research? You’re not alone! Research involves navigating tons of existing knowledge, and that’s where RRL comes in. But what exactly is RRL? Come and learn in this blog what is RRL in research .

What is the meaning of RRL in research?

In the world of studying and learning new things, you may come across the term “RRL.” But what does it mean? RRL stands for “Related Literature Review. ” This refers to the part of a research study where existing literature, studies, and findings related to the topic being investigated are reviewed and analyzed. It involves examining what other researchers have already discovered and published about the subject.

RRL is an important aspect of any research task as it helps researchers understand the current state of knowledge in their field. By reviewing existing literature, researchers can identify gaps in knowledge, determine the significance of their study, and build upon the work of others.

Understanding the Role of RRL in Research

Related Literature Review (RRL) plays a significant role in research by providing a foundation for the study. It helps researchers in the following ways:

i. Gain Insights:

By reviewing existing literature, researchers can gain valuable insights into the topic they are studying. This allows them to understand the context, theories, methodologies, and findings related to their research area.

ii. Identify Gaps:

RRL helps researchers identify gaps or areas where further research is needed. By analyzing existing literature, researchers can pinpoint unanswered questions or inconsistencies in previous studies, paving the way for new research avenues.

iii. Justify Research:

RRL helps researchers justify the significance of their study. By demonstrating how their research builds upon or contributes to existing literature, researchers can highlight the relevance and importance of their work.

iv. Avoid Duplication:

By looking at what others have already studied, researchers can make sure they don’t repeat the same research that has already been done. This ensures that research efforts are focused on addressing new questions or expanding existing knowledge rather than replicating what has already been done.

Example of RRL in Research

To better understand the concept of RRL, let’s consider an example of RRL research. Imagine a researcher is conducting a study on the effects of exercise on mental health. Before designing their study, they would conduct a Related Literature Review to examine what previous research has revealed about this topic.

During their RRL, the researcher finds several studies that have investigated the relationship between exercise and mental health. They discover that existing literature suggests a positive correlation between regular exercise and improved mental well-being.

Based on this information, the researcher identifies a gap in the literature regarding the specific types of exercises that are most beneficial for mental health. This gap motivates them to design a study focusing on different types of exercises and their effects on mental health outcomes.

By conducting a thorough RRL, the researcher not only gains a deeper understanding of the topic but also identifies a unique research question to explore further.

Importance of RRL in Research

Related Literature Review (RRL) holds significant importance in the research process. It serves as a cornerstone for any research study and offers numerous benefits to researchers. Here is the following importance of RRL in research:

i. Establishing Context and Background

One of the primary purposes of RRL is to establish the context and background for a research study. By reviewing existing literature, researchers can understand the historical development, key concepts, and foundational theories related to their topic.

ii. Justifying the Research

RRL helps researchers justify their study by demonstrating its relevance and significance in the broader context of existing literature. By highlighting gaps or limitations in previous research, researchers can articulate how their study contributes to filling these gaps or addressing unanswered questions.

iii. Identifying Research Gaps

Another essential aspect of RRL is its role in identifying research gaps. By analyzing existing literature, researchers can identify areas where further investigation is needed. This helps in shaping the research question and designing a study that addresses these gaps, thus advancing the field’s knowledge.

What is the purpose of RRL in research?

Understanding the purpose of Related Literature Review (RRL) is important for researchers beginning a new study. Let’s see the various purposes of RRL research:

i. Providing a Comprehensive Overview

One of the primary purposes of RRL is to provide researchers with a comprehensive overview of literature related to their topic. By reviewing a wide range of studies, researchers can gain insights into the various perspectives, methodologies, and findings that have been explored by other scholars.

ii. Evaluating Methodologies and Findings

RRL allows researchers to evaluate the methodologies and findings of previous studies. By critically analyzing the strengths and weaknesses of existing research, researchers can identify potential methodological approaches for their study and assess the reliability and validity of previous findings.

iii. Guiding Research Design

RRL plays a crucial role in guiding the design of new research studies. By identifying gaps, inconsistencies, or unresolved questions in existing literature, researchers can shape their research questions, hypotheses, and methodologies to address these areas effectively.

iv. Informing Theoretical Frameworks

RRL helps researchers develop and refine theoretical frameworks for their study. By synthesizing existing theories and conceptual models from the literature, researchers can build a solid foundation for their research and situate their study within the broader theoretical context of their field.

v. Illustrating Significance and Relevance

RRL helps researchers illustrate the significance and relevance of their study within the broader scholarly discourse. By showcasing how their research builds upon or contributes to existing literature, researchers can justify the importance of their study and its potential impact on the field.

What is RRL in practical research?

Related Literature Review (RRL) is not just a theoretical exercise; it has practical implications for researchers conducting empirical studies. Let’s explore how RRL is applied in practical research settings.

i. Informing Research Design and Methodology

In practical research, RRL informs the design and methodology of the study. By reviewing existing literature, researchers can identify appropriate research methods, data collection techniques, and analytical approaches that have been used successfully in previous studies addressing similar research questions.

ii. Providing Baseline Data and Comparisons

RRL provides researchers with baseline data and comparisons for their study. By examining previous findings and results, researchers can establish benchmarks against which they can compare their own findings. This allows researchers to contextualize their results within the existing body of knowledge and assess the novelty and significance of their contributions.

iii. Identifying Variables and Constructs

RRL helps researchers identify relevant variables and constructs for their study. By reviewing conceptual frameworks and theoretical models from existing literature, researchers can identify key variables, constructs, and relationships that need to be considered in their research design.

iv. Supporting Data Interpretation and Discussion

RRL supports data interpretation and discussion in practical research. By grounding their findings in existing literature, researchers can provide a meaningful interpretation of their results and discuss their implications within the context of previous studies. This strengthens the validity and credibility of their findings and enhances the overall quality of the research.

What is RRL in quantitative research?

Related Literature Review (RRL) plays a crucial role in quantitative research by providing a foundation for the study and informing various aspects of the research process. Let’s explore how RRL in quantitative research works:

i. Guiding Hypothesis Development

In quantitative research, RRL guides the development of hypotheses or research questions. By reviewing existing literature, researchers can identify gaps, patterns, or trends that suggest potential relationships or associations to explore in their own study.

ii. Informing Sample Selection and Data Collection

RRL informs sample selection and data collection in quantitative research. By examining previous studies, researchers can identify appropriate sampling techniques, sample sizes, and data collection methods that have been used effectively in similar studies.

iii. Validating Measurement Instruments

RRL helps validate measurement instruments in quantitative research. By reviewing previous studies that have used similar measures, researchers can assess the reliability and validity of measurement instruments and determine their suitability for their study.

iv. Providing Comparative Analysis

RRL facilitates comparative analysis in quantitative research. By comparing their findings to existing literature, researchers can assess the consistency or divergence of their results and contribute to the ongoing dialogue within the field.

What is RRL in Research Paper?

Related Literature Review (RRL) is an essential component of any research paper. It serves several key purposes and contributes to the overall quality and credibility of the paper. Let’s explore the specific role of RRL in research papers.

i. Establishing Context and Justifying Research

One of the primary functions of RRL in a research paper is to establish the context for the study and justify its significance. By reviewing existing literature, researchers can demonstrate the relevance of their study within the broader scholarly discourse and articulate its contribution to filling gaps or addressing unanswered questions in the field.

ii. Providing a Theoretical Framework

RRL provides a theoretical framework for the research paper. By synthesizing existing theories, conceptual models, and empirical findings from the literature, researchers can build a solid foundation for their study and situate it within the broader theoretical context of their field.

iii. Supporting Methodological Choices and Data Interpretation

RRL supports methodological choices and data interpretation in the research paper. By reviewing previous studies, researchers can justify their methodological approach, sampling techniques, and data analysis methods. Additionally, RRL provides a basis for interpreting the findings of the study within the context of existing literature.

iv. Enhancing Credibility and Validity

Finally, RRL enhances the credibility and validity of the research paper. By grounding the study in existing literature, researchers demonstrate a thorough understanding of the topic and its historical development. This strengthens the overall argument and contributes to the paper’s credibility as a scholarly contribution to the field.

In conclusion, Related Literature Review (RRL) is a fundamental aspect of the research process with far-reaching implications for academic inquiry. By reviewing existing literature, researchers can gain insights, identify gaps, and justify the significance of their study. RRL informs various aspects of the research process, including research design, methodology, data interpretation, and theoretical framework. It enhances the credibility and validity of research endeavors and contributes to the ongoing dialogue within the field.

As researchers begin on their studies, it’s essential to recognize the importance of RRL and its role in shaping the trajectory of research inquiry. By conducting a thorough RRL, researchers can build upon the work of others, advance the field’s knowledge, and make meaningful contributions to their respective disciplines.

1. What is the difference between RRL and a literature review?

RRL specifically refers to the part of a research study where existing literature related to the topic being investigated is reviewed and analyzed. In contrast, a literature review is a broader overview of existing literature on a particular topic, which may or may not be part of a research study.

2. How do researchers conduct a Related Literature Review (RRL)?

Researchers conduct RRL by systematically searching for and reviewing existing literature related to their research topic. This involves using academic databases, libraries, and other sources to gather relevant studies, articles, and publications. Researchers then analyze and synthesize the findings, identifying key themes, trends, and gaps in the literature.

3. Can RRL be conducted for any type of research study?

Yes, RRL can be conducted for various types of research studies, including quantitative, qualitative, and mixed-methods approaches. Regardless of the research methodology, conducting a thorough RRL is essential for establishing the context, justifying the research, and informing various aspects of the study.

4. How do researchers incorporate RRL into their research papers?

Researchers incorporate RRL into their research papers by dedicating a section specifically to reviewing and discussing existing literature related to their topic. This section typically precedes the methodology and findings sections of the paper and provides a comprehensive overview of relevant studies, theories, and findings that inform the current study.

5. Is RRL the same as a literature review in a research paper?

While RRL is a component of a literature review in a research paper, they are not the same. RRL specifically focuses on reviewing literature related to the research topic being investigated, whereas a literature review in a research paper may include a broader overview of literature relevant to the study’s context, theoretical framework, and methodology.

Leave a Comment Cancel Reply

Your email address will not be published. Required fields are marked *

Save my name, email, and website in this browser for the next time I comment.

Literature Review: Google Scholar

• Sample Searches
• Examples of Published Literature Reviews
• Researching Your Topic
• Subject Searching
• Google Scholar
• Track Your Work
• Citation Managers This link opens in a new window
• Citation Guides This link opens in a new window
• Tips on Writing Your Literature Review This link opens in a new window
• Research Help

Google Scholar Library Links

To see links to BenU Library subscription content in your Google Scholar search results:

• Go to Google Scholar > Settings > Library Links
• Search " Benedictine "
• Check the boxes
• Click Save and you're done!
• Google Scholar Library Links Tutorial This tutorial will guide you step-by-step through the quick setup process.

Finding Academic Literature

• 8 Winning hacks to use Google Scholar for your research paper

Ask a Librarian

Chat with a Librarian

Lisle: (630) 829-6057 Mesa: (480) 878-7514 Toll Free: (877) 575-6050 Email: [email protected]

Book a Research Consultation Library Hours

• << Previous: Subject Searching
• Next: Track Your Work >>
• Last Updated: Apr 25, 2024 3:34 PM
• URL: https://researchguides.ben.edu/lit-review

Kindlon Hall 5700 College Rd. Lisle, IL 60532 (630) 829-6050

Gillett Hall 225 E. Main St. Mesa, AZ 85201 (480) 878-7514

Educational resources and simple solutions for your research journey

How to Write a Thematic Literature Review: A Beginner’s Guide

Literature reviews provide a comprehensive understanding of existing knowledge in a particular field, offer insights into gaps and trends, and ultimately lay the foundation for innovative research. However, when tackling complex topics spanning multiple issues, the conventional approach of a standard literature review might not suffice. Many researchers present a literature review without giving any thought to its organization or structure, but this is where a thematic literature review comes into play. In this article, we will explore the significance of thematic reviews, delve into how and when to undertake them, and offer invaluable guidance on structuring and crafting a compelling thematic literature review.

Table of Contents

What is a thematic literature review?

A thematic literature review, also known as a thematic review, involves organizing and synthesizing the existing literature based on recurring themes or topics rather than a chronological or methodological sequence. Typically, when a student or researcher works intensively on their research there are many sub-domains or associated spheres of knowledge that one encounters. While these may not have a direct bearing on the main idea being explored, they provide a much-needed background or context to the discussion. This is where a thematic literature review is useful when dealing with complex research questions that involve multiple facets, as it allows for a more in-depth exploration of specific themes within the broader context.

When to opt for thematic literature review?

It is common practice for early career researchers and students to collate all the literature reviews they have undertaken under one single broad umbrella. However, when working on a literature review that involves multiple themes, lack of organization and structure can slow you down and create confusion. Deciding to embark on a thematic literature review is a strategic choice that should align with your research objectives. Here are some scenarios where opting for a thematic review is advantageous:

• Broad Research Questions: When your research question spans across various dimensions and cannot be adequately addressed through a traditional literature review.
• Interdisciplinary Research: In cases where your research draws from multiple disciplines, a thematic review helps in synthesizing diverse literature cohesively.
• Emerging Research Areas: When exploring emerging fields or topics with limited existing literature, a thematic review can provide valuable insights by focusing on available themes.
• Complex Issues: Thematic reviews are ideal for dissecting complex issues with multiple contributing factors or dimensions.

Advantages of a Thematic Literature Review

With better comprehension and broad insights, thematic literature reviews can help in identifying possible research gaps across themes. A thematic literature review has several advantages over a general or broad-based approach, especially for those working on multiple related themes.

• It provides a comprehensive understanding of specific themes within a broader context, allowing for a deep exploration of relevant literature.
• Thematic reviews offer a structured approach to organizing and synthesizing diverse sources, making it easier to identify trends, patterns, and gaps.
• Researchers can focus on key themes, enabling a more detailed analysis of specific aspects of the research question.
• Thematic reviews facilitate the integration of literature from various disciplines, offering a holistic view of the topic.
• Researchers can provide targeted recommendations or insights related to specific themes, aiding in the formulation of research hypotheses.

Now that we know the benefits of a thematic literature review, what is the best way to arrange reviewed literature in a thematic format?

How to write a thematic literature review

To effectively structure and write a thematic literature review, follow these key steps:

• Define Your Research Question: Clearly define the overarching research question or topic you aim to explore thematically. When writing a thematic literature review, go through different literature review sections of published research work and understand the subtle nuances associated with this approach.
• Identify Themes: Analyze the literature to identify recurring themes or topics relevant to your research question. Categorize the bibliography by dividing them into relevant clusters or units, each dealing with a specific issue. For example, you can divide a topic based on a theoretical approach, methodology, discipline or by epistemology. A theoretical review of related literature for example, may also look to break down geography or issues pertaining to a single country into its different parts or along rural and urban divides.
• Organize the Literature: Group the literature into thematic clusters based on the identified themes. Each cluster represents a different aspect of your research question. It is up to you to define the different narratives of thematic literature reviews depending on the project being undertaken; there is no one formal way of doing this. You can weigh how specific areas stack up against others in terms of existing literature or studies and how many more aspects may need to be added or further looked into.
• Review and Synthesize: Within each thematic cluster, review and synthesize the relevant literature, highlighting key findings and insights. It is recommended to identify any theme-related strengths or weaknesses using an analytical lens.
• Integrate Themes: Analyze how the themes interact with each other, draw linkages between earlier studies and see how they contribute to your own research. A thematic literature review presents readers with a comprehensive overview of the literature available on and around the research topic.
• Provide a Framework: Develop a framework or conceptual model that illustrates the relationships between the themes. Present the most relevant part of the thematic review toward the end and study it in greater detail as it reflects the literature most relevant and directly related to the main research topic.
• Conclusion: Conclude your thematic literature review by summarizing the key findings and their implications for your research question. Be sure to highlight any gaps or areas requiring further investigation in this section.
• Cite and Reference: It is important to remember that a thematic review of literature for a PhD thesis or research paper lends greater credibility to the student or researcher. So ensure that you properly cite and reference all sources according to your chosen citation style.
• Edit and Proofread: Take some time to review your work, ensure proper structure and flow and eliminate any language, grammar, or spelling errors that could deviate reader attention. This will help you deliver a well-structured and elegantly written thematic literature review.

Thematic literature review example

In essence, a thematic literature review allows researchers to dissect complex topics into smaller manageable themes, providing a more focused and structured approach to literature synthesis. This method empowers researchers to gain deeper insights, identify gaps, and generate new knowledge within the context of their research.

To illustrate the process mentioned above, let’s consider an example of a thematic literature review in the context of sustainable development. Imagine the overarching research question is: “What are the key factors influencing sustainable urban planning?” Potential themes could include environmental sustainability, social equity, economic viability, and governance. Each theme would have a dedicated section in the review, summarizing relevant literature and discussing how these factors intersect and impact sustainable urban planning. Close with a strong conclusion that highlights research gaps or areas of investigation. Finally, review and refine the thematic literature review, adding citations and references as required.

In conclusion, when tackling multifaceted research questions, a thematic literature review proves to be an indispensable tool for researchers and students alike. By adopting this approach, scholars can navigate the intricate web of existing literature, unearth meaningful patterns, and contribute to the advancement of knowledge in their respective fields. We hope the information in this article helps you create thematic reviews that illuminate your path to new discoveries and innovative insights.

R Discovery is a literature search and research reading platform that accelerates your research discovery journey by keeping you updated on the latest, most relevant scholarly content. With 250M+ research articles sourced from trusted aggregators like CrossRef, Unpaywall, PubMed, PubMed Central, Open Alex and top publishing houses like Springer Nature, JAMA, IOP, Taylor & Francis, NEJM, BMJ, Karger, SAGE, Emerald Publishing and more, R Discovery puts a world of research at your fingertips.  

Try R Discovery Prime FREE for 1 week or upgrade at just US$72 a year to access premium features that let you listen to research on the go, read in your language, collaborate with peers, auto sync with reference managers, and much more. Choose a simpler, smarter way to find and read research – Download the app and start your free 7-day trial today !  

Related Posts

How to Write a Research Paper Outline (with Examples)

How to Read, Write, Promote Your Research Effectively: Timesaving Solution for Busy Researchers

• Walden University
• Faculty Portal

Common Assignments: Literature Review Matrix

Literature review matrix.

As you read and evaluate your literature there are several different ways to organize your research. Courtesy of Dr. Gary Burkholder in the School of Psychology, these sample matrices are one option to help organize your articles. These documents allow you to compile details about your sources, such as the foundational theories, methodologies, and conclusions; begin to note similarities among the authors; and retrieve citation information for easy insertion within a document.

You can review the sample matrixes to see a completed form or download the blank matrix for your own use.

• Literature Review Matrix 1 This PDF file provides a sample literature review matrix.
• Literature Review Matrix 2 This PDF file provides a sample literature review matrix.
• Literature Review Matrix Template (Word)
• Literature Review Matrix Template (Excel)

Related Resources

Didn't find what you need? Email us at [email protected] .

• Previous Page: Commentary Versus Opinion
• Next Page: Professional Development Plans (PDPs)
• Office of Student Disability Services

Walden Resources

Departments.

• Academic Residencies
• Academic Skills
• Career Planning and Development
• Customer Care Team
• Field Experience
• Military Services
• Student Success Advising
• Writing Skills

Centers and Offices

• Center for Social Change
• Office of Academic Support and Instructional Services
• Office of Degree Acceleration
• Office of Research and Doctoral Services
• Office of Student Affairs

Student Resources

• Doctoral Writing Assessment
• Form & Style Review
• Quick Answers
• ScholarWorks
• SKIL Courses and Workshops
• Walden Bookstore
• Walden Catalog & Student Handbook
• Student Safety/Title IX
• Legal & Consumer Information
• Website Terms and Conditions
• Cookie Policy
• Accessibility
• Accreditation
• State Authorization
• Net Price Calculator
• Contact Walden

Walden University is a member of Adtalem Global Education, Inc. www.adtalem.com Walden University is certified to operate by SCHEV © 2024 Walden University LLC. All rights reserved.

Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design (2020)

Chapter: chapter 2 - literature review and synthesis.

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

4 Literature Review and Synthesis Literature Review Purpose of Literature Review Performance-based seismic design (PBSD) for infrastructure in the United States is a developing field, with new research, design, and repair technologies; definitions; and method- ologies being advanced every year. A synthesis report, NCHRP Synthesis 440: Performance- Based Seismic Bridge Design (Marsh and Stringer 2013), was created to capture PBSD understanding up to that point. This synthesis report described the background, objec- tives, and research up until 2011 to 2012 and synthesized the information, including areas where knowledge gaps existed. The literature review in this research report focuses on new infor mation developed after the efforts of NCHRP Synthesis 440. The intention is that this research report will fuel the next challenge: developing a methodology to implement PBSD for bridge design. Literature Review Process Marsh and Stringer (2013) performed an in-depth bridge practice review by sending a questionnaire to all 50 states, with particular attention to regions with higher seismic hazards. The survey received responses from a majority of those agencies. This process was continued in the current project with a request for new information or research that the state depart- ment of transportation (DOT) offices have participated in or are aware of through other organizations. The research team reached out to the list of states and researchers in Table 1. An X within a box is placed in front of their names if they responded. The team also examined the websites of the state DOTs that participated to investigate whether something was studied locally, especially work being developed in California. The research team made an additional effort to perform a practice review of bridge designs, research, and other design industries, specifically in the building industry. The building industry has been developing PBSD for more than 20 years, and some of their developments are appli- cable to bridge design. These combined efforts have allowed the research team to assemble an overview of the state of PBSD engineering details and deployment since Marsh and Stringer’s (2013) report was published. NCHRP Synthesis 440 primarily dealt with the effects of strong ground motion shaking. Secondary effects such as tsunami/seiche, ground failure (surface rupture, liquefaction, or slope failure), fire, and flood were outside the scope of this study. Regardless, their impact on bridges may be substantial, and investigation into their effects is undoubtedly important. C H A P T E R 2

Literature Review and Synthesis 5 The following e-mail was sent to the owners and researchers. Dear (individual): We are assisting Modjeski & Masters with the development of proposed guidelines for Performance- Based Seismic Bridge Design, as part of NCHRP [Project] 12-106. Lee Marsh and our Team at BergerABAM are continuing our efforts from NCHRP Synthesis 440, which included a literature review up to December of 2011. From this timeframe forward, we are looking for published research, contractual language, or owner documents that deal with the following categories: 1. Seismic Hazards (seismic hazard levels, hazard curves, return periods, geo-mean vs. maximum direc- tion, probabilistic vs. deterministic ground motions, conditional mean spectrum, etc.) 2. Structure Response (engineering design parameters, materials and novel columns, isolation bearings, modeling techniques, etc.) 3. Damage Limit States (performance descriptions, displacement ductility, drift ratios, strain limits, rotation curvature, etc.) 4. Potential for Loss (damage descriptions, repairs, risk of collapse, economical loss, serviceability loss, etc.) 5. Performance Design Techniques (relating hazard to design to performance to risk, and how to assess [these] levels together) If you are aware of this type of resource, please provide a contact that we can work with to get this information or provide a published reference we can gather. Your assistance is appreciated. We want to minimize your time, and ask that you respond by Wednesday, 8 February 2017. Thank you again, Research Team Synthesis of PBSD (2012–2016) Objectives of NCHRP Synthesis 440 The synthesis gathered data from a number of different but related areas. Marsh and Stringer (2013), herein referred to as NCHRP Synthesis 440, set the basis for this effort. The research report outline follows what has been added to the NCHRP Synthesis 440 effort since 2012. The information gathered that supplements NCHRP Synthesis 440 includes, but is not limited to, the following topics. • Public and engineering expectations of seismic design and the associated regulatory framework Participation State Alaska DOT Arkansas DOT California DOT (Caltrans) Illinois DOT Indiana DOT Missouri DOT Montana DOT Nevada DOT Oregon DOT South Carolina DOT Utah DOT Washington State DOT Table 1. List of state DOT offices and their participation.

6 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design • Seismic hazard analysis • Structural analysis and design • Damage analysis • Loss analysis • Organization-specific criteria for bridges • Project-specific criteria Where new or updated information is available for these areas, a summary is included. Marsh and Stringer (2013) also identified gaps in the knowledge base of PBSD, current as of 2012, that need to be closed. Knowledge gaps certainly exist in all facets of PBSD; however, key knowledge gaps that should be closed in order to implement PBSD are covered. • Gaps related to seismic hazard prediction • Gaps related to structural analysis • Gaps related to damage prediction • Gaps related to performance • Gaps related to loss prediction • Gaps related to regulatory oversight and training • Gaps related to decision making These knowledge gaps have been filled in somewhat in this research report but, for the most part, these areas are still the key concepts that require additional development to further the development of a PBSD guide specification. Public and Engineering Expectations of Seismic Design and the Associated Regulatory Framework The public expectation of a structure, including a bridge, is that it will withstand an earthquake, but there is a limited understanding of what that actually means. Decision makers struggle to understand how a bridge meeting the current requirements of the AASHTO Guide Specifications for LRFD Seismic Bridge Design (2011), herein referred to as AASHTO guide specifications, will perform after either the expected (design) or a higher level earthquake. Decision makers understand the basis of life safety, wherein the expectation is that no one will perish from a structure collapsing, but often mistakenly believe that the structure will also be usable after the event. In higher level earthquakes, even in some lower level events, this is not true without repair, retrofit, or replacement. In the past decade, there has been an increased awareness by owners and decision makers as to the basis of seismic design. As a result, a need has developed for performance criteria so that economic and social impacts can be interwoven with seismic design into the decision processes (see Figure 1). Several states, including California, Oregon, and the State of Washington, are working toward resiliency plans, although these are developed under different titles or programs within the states. Resiliency has been defined in several ways: (1) amount of damage from an event measured in fatalities, structural replacement cost, and recovery time and (2) the time to resto- ration of lifelines, reoccupation of homes and structures, and, in the short term, resumption of normal living routines. The California DOT Caltrans has generated risk models and is in the process of developing a new seismic design specification to address PBSD in bridge design. The risk models and specifications are not published yet, but the use in PBSD is discussed in greater detail later in this chapter.

Literature Review and Synthesis 7 The State of Washington The State of Washington’s resiliency plan, outlined in Washington State Emergency Management Council–Seismic Safety Committee (2012), works to identify actions and policies before, during, and after an earthquake event that can leverage existing policies, plans, and initiatives to realize disaster resilience within a 50-year life cycle. The hazard level used for trans- portation planning is the 1000 year event. The goals for transportation systems vary depending on the type of service a route provides, as shown in following components of the plan. For major corridors such as Interstates 5, 90, and 405 and floating bridges SR 520, I-90, and Hood Canal, the target timeframe for response and recovery is between 1 to 3 days and 1 to 3 months, depending on location. The current anticipated timeframe based on current capacity and without modifications is between 3 months to 1 year and 1 to 3 years, depending on location. The actual response and recovery time will depend on a number of factors. For example: 1. The number of Washington State DOT personnel who are able to report to work may be limited by a variety of circumstances, including where personnel were at the time of the earthquake and whether they sustained injuries. 2. Bridges and roadways in earthquake-affected areas must be inspected. How long this takes will depend on the number and accessibility of the structures and the availability of qualified inspectors. 3. Some bridges and segments of road may be rendered unusable or only partially usable as a result of the earthquake or secondary effects. The response and recovery timeframe will depend on the number, the location, and the extent of the damage. 4. Certain earthquake scenarios could result in damage to the Ballard Locks and cause the water level in Lake Washington to drop below the level required to operate the floating bridges. 5. Depending on the scenario and local conditions, liquefaction and slope failure could damage both interstates and planned detours. During the first 3 days after the event, the Washington State Department of Transportation (Washington State DOT) will inspect bridges and begin repairs as needed. Washington State DOT’s first priority will be to open key routes for emergency response vehicles. Subsequent phases of recovery will include setting up detours where necessary and regulating the type and Figure 1. PBSD decision-making process (Guidelines Figure 2.0-1). References to guidelines figures and tables within parentheses indicate the proposed AASHTO guidelines.

8 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design volume of traffic, to give the public as much access as possible while damaged roads and bridges are repaired. For major and minor arterials, which encompass arterial roadways (including bridges) other than the interstates (so therefore includes state highways and many city and county roads), the target timeframe for response and recovery is between 0 to 24 hours and 3 months to 1 year, depending on location; the percentage of roadways that are open for use will increase over this period. Anticipated timeframe based on current capacity is between 1 week to 1 month and 1 to 3 years, depending on location; the percentage of roadways that are open for use will increase over this period. The goal of Washington State Emergency Management Council’s resiliency plan is to establish a means to coordinate agencies, public–private partnerships, and standards toward these resiliency goals. The plan outlines goals for recovery times for transportation systems in terms of hours, days, weeks, months, and years, with targets to achieve different levels of recovery (see Table 2) as follows. Similar recovery timeframe processes were established for service sectors (e.g., hospitals, law enforcement, and education); utilities; ferries, airports, ports, and navigable waterways; mass transit; and housing. The overall resiliency plan also discusses the degree to which the recovery of one component or sector would depend on the restoration of another. The key interdependencies that the participants identified include information and communication technologies, transportation, electricity, fuel, domestic water supplies, wastewater systems, finance and banking, and planning and community development. It appears that the implementation of the Washington State Emergency Management Council’s initiative, originally assumed to take 2.5 to 3 years in 2012, has not seen significant development since then. However, the State’s initiative to develop a more resilient community has been extended down to the county level, with King County’s efforts referenced in Rahman et al. (2014) and, at the city level, with the City of Seattle referenced in CEMP (2015). This reflects the commitment needed not only by the legislature and the state departments but also by other agencies (e.g., county, city, or utilities) and the public to take an interest in, and provide funding for, the development of a resiliency plan. The recovery continuum is presented graphically in Figure 2. Developing this relationship with other agency plans is an iterative process that will take time, as shown in Figure 3. Identifying the critical sectors of the agency is necessary to develop a resiliency model and determine how to approach a disaster recovery framework. King County worked from Washington State’s initiative to develop Figure 4. The Oregon DOT Oregon DOT has developed a variation of the approach identified by the State of Wash- ington; further discussion is found later in this chapter. Other Resilience Documents The building industry has recently seen the development of two additional documents that address PBSD in terms of expectations and process. The REDi Rating System from REDi (2013) sets an example for incorporating resilience- based design into the PBSD process. This document outlines structural resilience objectives for organizational resilience, building resilience, loss assessment, and ambient resilience to evaluate and rate the decision making and design methodology using PBSD for a specific project.

Literature Review and Synthesis 9 The document is one of the only references that addresses a system to develop probabilistic methods to estimate downtime. The overall intent is to provide a roadmap to resilience. This roadmap is intended to allow owners to resume business operation and to provide livable conditions quickly after an earthquake. The Los Angeles Tall Buildings Structural Design Council (LATBSDC 2014) created an alter- native procedure specific to their location. Design specification criteria are identified and modi- fications are described as appropriate for the PBSD approach to tall buildings in this localized Minimal (A minimum level of service is restored, primarily for the use of emergency responders, repair crews, and vehicles transporting food and other critical supplies.) Functional (Although service is not yet restored to full capacity, it is sufficient to get the economy moving again—for example, some truck/freight traffic can be accommodated. There may be fewer lanes in use, some weight restrictions, and lower speed limits.) Operational (Restoration is up to 80 to 90 percent of capacity: A full level of service has been restored and is sufficient to allow people to commute to school and to work.) Time needed for recovery to 80 to 90 percent operational given current conditions. Source: Washington State Emergency Management Council–Seismic Safety Committee (2012). Table 2. Washington State’s targets of recovery.

10 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Source: Adapted from FHWA by CEMP (2015). Figure 2. Recovery continuum process. Source: CEMP (2015). Figure 3. Relationship of disaster recovery framework to other city plans. region. This procedure is a good example of how PBSD criteria and methodology need to be established locally, with a knowledge of risk, resources, and performance needs in order to set the criteria for true PBSD. Seismic Hazard Prediction As outlined in NCHRP Synthesis 440, the seismic hazard includes the regional tectonics and the local site characteristics from either a deterministic or probabilistic viewpoint. The deterministic form allows the assessment of shaking at a site as a function of the controlling earthquake that can occur on all the identified faults or sources. The probabilistic approach

Literature Review and Synthesis 11 defines an acceleration used in design that would be exceeded during a given window of time (e.g., a 7% chance of exceedance in 75 years). The following subsections provide a summary of procedures currently used within AASHTO, as well as new issues that should be eventually addressed in light of approaches used by the building industry. AASHTO Probabilistic Approach As summarized in the AASHTO guide specifications, the current approach used by AASHTO involves the use of a probabilistic hazard model with a nominal return period of 1000 years. Baker (2013) noted that the probabilistic seismic hazard analysis involves the following five steps: 1. Identify all earthquake sources capable of producing damaging ground motions. 2. Characterize the distribution of earthquake magnitudes (the rates at which earthquakes of various magnitudes are expected to occur). 3. Characterize the distribution of source-to-site distances associated with potential earthquakes. 4. Predict the resulting distribution of ground motion intensity as a function of earthquake magnitude, distance, and so forth. 5. Combine uncertainties in earthquake size, location, and ground motion intensity, using a calculation known as the total probability theorem. While implementation of the five steps in the probabilistic approach is beyond what most practicing bridge engineers can easily perform, AASHTO, working through the U.S. Geological Survey, developed a website hazard tool that allows implementation of the probabilistic proce- dure based on the latitude and longitude of a bridge site. The product of the website includes peak ground acceleration (PGA), spectral acceleration at 0.2 s (Ss), and spectral acceleration at 1 s (S1). These values are for a reference-site condition comprising soft rock/stiff soil, having a time-averaged shear wave velocity (Vs) over the upper 100 feet of soil profile equal to 2500 feet per second (fps). The Geological Survey website can also correct for local site conditions following procedures in the AASHTO Guide Specifications for LRFD Seismic Bridge Design. One of the limitations of the current U.S. Geological Survey hazard website is that it is based on a seismic hazard model developed in 2002. The Geological Survey updated its seismic model in 2008 and then in 2014; however, these updates are currently not implemented within the AASHTO hazard model on the Geological Survey’s website. Oregon and the State of Washington have updated the seismic hazard map used by the Oregon DOT and the Washington State Source: Rahman et al. (2014). Figure 4. Resilient King County critical sectors and corresponding subsectors.

12 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design DOT to include the 2014 U.S. Geological Survey hazard model; however, most state DOTs are still using the out-of-date hazard model. Use of the outdated hazard model introduces some inconsistencies in ground motion prediction, relative to the current Geological Survey hazard website tool at some locations. Discussions are ongoing between NCHRP and the U.S. Geological Survey to update the 2002 website tool. Another issue associated with the current AASHTO probabilistic method is that it is based on the geomean of the ground motion. In other words, the ground motion prediction equations in the hazard model are based on the geomean of recorded earthquake motions. These motions are not necessarily the largest motion. The building industry recognized that the maximum direction could result in larger ground motions and introduced maximum direction corrections. These corrections increase spectral acceleration by a factor of 1.1 and S1 by a factor of 1.3. The relevance of this correction to bridges is discussed in the next subsection of this review. The building industry also introduced a risk-of-collapse correction to the hazard model results. This correction is made to Ss and S1. The size of the correction varies from approximately 0.8 to 1.2 within the continental United States. It theoretically adjusts the hazard curves to provide a 1% risk of collapse in 50 years. The risk-of-collapse corrections were developed by the U.S. Geological Survey for a range of building structures located throughout the United States. Although no similar corrections have been developed for bridges, the rationale for the adjust- ment needs to be further evaluated to determine if the rationale should be applied to bridge structures. As a final point within this discussion of probabilistic methods within the AASHTO guide specifications, there are several other areas of seismic response that need to be considered. These include near-fault and basin effects on ground motions, as well as a long-period transition factor. The near-fault and basin adjustments correct the Ss and S1 spectral accelerations for locations near active faults and at the edge of basins, respectively. These adjustments typically increase spectral accelerations at longer periods (> 1 s) by 10% to 20%, depending on specifics of the site. The long-period transition identifies the point at which response spectral ordinates are no longer proportional to the 1/T decay with increasing period. These near-fault, basin, and long-period adjustments have been quantified within the building industry guidance documents but remain, for the most part, undefined within the AASHTO guide specifications. As bridge discussions and research move closer to true probabilistic format for PBSD, these issues need to be addressed as part of a future implementation process. Correction for Maximum Direction of Motion Over the last decade, a debate has been under way within the building industry regarding the appropriate definition of design response spectra (Stewart et al. 2011). The essence of the argument relates to the representation of bidirectional motion via response spectra. In both the AASHTO LRFD Bridge Design Specifications (2014), as well as the AASHTO Guide Specifications for LRFD Seismic Bridge Design (SGS), response spectra are established by defining spectral ordinates at two or three different periods from design maps developed by the U.S. Geological Survey for a return period of 1000 years. The resulting spectra are then adjusted for local site conditions, resulting in the final design spectra. In establishing the design maps for parameters such as Ss and S1, the U.S. Geological Survey has traditionally relied upon probabilistic seismic hazard analysis, which utilizes ground motion prediction equations (GMPEs) defined by the geometric mean of the two principal directions of recorded motion. In 2006, Boore introduced a new rotation independent geometric mean definition termed GMRotI50 (Boore et al. 2006). Then, in 2010, Boore developed a new defini- tion that does not rely upon the geometric mean termed RotD50 spectra, which can be generi- cally expressed as RotDNN spectra, where NN represents the percentile of response (i.e., 50 is

Literature Review and Synthesis 13 consistent with the median, 0 is the minimum, and 100 is the maximum). The NGA–West2 project GMPEs utilized RotD50 spectra for the ground motion models; however, the 2009 National Earthquake Hazards Reduction Program (NEHRP) provisions adopted a factor to modify the median response, RotD50, to the maximum possible response, RotD100 as the spectra for the design maps (Stewart et al. 2011). Introducing RotD100 resulted in a 10% to 30% increase in spectral ordinates results relative to the geometric mean, which has traditionally been used as a basis of seismic design. In order to appreciate the impact of these choices, a brief discussion of RotDNN spectra is warranted. As described in Boore (2010), for a given recording station, the two orthogonal- component time series are combined into a single time series corresponding to different rotation angles, as shown in Equation 1: aROT(t ; θ) = a1(t)cos(θ) + a2(t)sin(θ) (1) where a1(t ) and a2(t ) are the orthogonal horizontal component acceleration time series and θ is the rotation angle. For example, consider the two orthogonal horizontal component time series, H1 and H2, shown in Figure 5. The single time series corresponding to the rotation angle θ is created by combining the Direction 1 and Direction 2 time series. Then, the response spectrum for that single time series can be obtained, as shown in the figure. The process is repeated for a range of azimuths from 0° to one rotation-angle increment less than 180°. If the rotation-angle increment is θ, then there will be 180/θ single time series, as well as 180/θ corresponding response spectra. For example, if θ = 30°, then there will be six single time series (the original two, as well as four generated time series), as well as six response spectra, as shown in Figure 6. Once the response spectra for all rotation angles are obtained, then the nth percentile of the spectral amplitude over all rotation angles for each period is computed (e.g., RotD50 is the median value and RotD100 is the largest value for all rotation angles). For example, at a given period of 1 s, the response spectra values for all rotation angles are sorted, and the RotD100 value would be the largest value from all rotation angles while RotD50 would be the median. This is repeated for all periods, with potentially different rotation angles, producing the largest Source: Palma (2019). Figure 5. Combination of time series to generate rotation dependent spectra.

14 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design response at any given period (period-dependent rotation angle.) Figure 7 shows an example of the two orthogonal horizontal components, as well as the RotD50 and RotD100 spectra for the as-recorded ground motion from the 2011 Christchurch, New Zealand, earthquake at Kaiapoi North School station. As can be seen in the sample spectra (see Figure 7), the RotD100 spectrum represents a sub- stantial increase in demand when compared with the RotD50 spectrum. The main question facing the bridge community from this point onward is the appropriate selection of response spectra definition. This question can only be answered by developing sample designs to both the RotD50 and RotD100 spectra, which would then be evaluated via no-linear time history analysis. Such a study will require multiple bridge configurations and multiple ground motions. As an example of the potential impact, Figure 8 shows the results of a single-degree-of- freedom bridge column designed according to both RotD50 and RotD100 spectra, along with the resulting nonlinear time history analysis. The column was designed using direct displacement- based design to achieve a target displacement of 45 cm. It is clear from the results in Figure 8d that the nonlinear response of the column designed to the RotD100 spectrum matches the target Source: Palma (2019). Figure 6. Example of time series rotations with an angle increment (p) of 30ç. Source: Palma (2019). Figure 7. Sample spectra for a recorded ground motion pair.

Literature Review and Synthesis 15 reasonably well, while designing to the RotD50 spectrum results in displacements that are much greater than expected. This is, of course, only one result of an axisymmetric system. In the future (and outside the scope of this project), a systematic study could be conducted for both single degree of freedom and multiple degrees of freedom systems. The literature on this topic can be divided into two categories: (1) response spectra definitions and (2) impact on seismic response. The majority of the literature addresses the former. For example, Boore et al. (2006) and Boore (2010) introduced orientation-independent measures of seismic intensity from two horizontal ground motions. Boore et al. (2006) proposed two measures of the geometric mean of the seismic intensity, which are independent of the in-situ orientations of the sensors. One measure uses period-dependent rotation angles to quantify the spectral intensity, denoted GMRotDnn. The other measure is the GMRotInn, where I stands for period-independent. The ground motion prediction equations of Abrahamson and Silva (1997), Figure 8. Single bridge column designed according to both RotD50 and RotD100 spectra (Tabas EQ = Tabas earthquake and displ. = displacement).

16 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Boore et al. (1997), Campbell and Bozorgnia (2003), and Sadigh et al. (1997) have been updated using GMRotI50 as the dependent variable. Since more users within the building industry expressed the desire to use the maximum spec- tral response over all the rotation angles without geometric means, Boore (2010) introduced the measures of ground-shaking intensity irrespective of the sensor orientation. The measures are RotDnn and RotInn, whose computation is similar to GMRotDnn and GMRotInn without computing the geometric means. With regard to impact on seismic response, the opinion paper by Stewart et al. (2011) and the work by Mackie et al. (2011) on the impact of incidence angle on bridge response are relevant. Specifically, Stewart et al. (2011) noted the importance of computational analysis of structures (which had not been done as of 2011) in proposing appropriate spectra definitions. Other Methodologies for Addressing Seismic Ground Motion Hazards There are several other reports that address the question of the methodology that may be utilized in developing the seismic hazard. These recent studies endeavored to create a method- ology that is easier for engineers, as users, to understand how to tie the seismic hazard to the performance expectation. The variability of these approaches also demonstrates the broad range of options and therefore a limited understanding by practitioners in the bridge design industry. Following are some examples that apply to PBSD. Wang et al. (2016) performed a probabilistic seismic risk analysis (SRA) based on a single ground motion parameter (GMP). For structures whose responses can be better predicted using multiple GMPs, a vector-valued SRA (VSRA) gives accurate estimates of risk. A simplified approach to VSRA, which can substantially improve computational efficiency without losing accuracy, and a new seismic hazard de-aggregation procedure are proposed. This approach and the new seismic hazard de-aggregation procedure would allow an engineer to determine a set of controlling earthquakes in terms of magnitude, source–site distance, and occurrence rate for the site of interest. Wang et al. presented two numerical examples to validate the effectiveness and accuracy of the simplified approach. Factors affecting the approximations in the simplified approach were discussed. Kwong and Chopra (2015) investigated the issue of selecting and scaling ground motions as input excitations for response history analyses of buildings in performance-based earthquake engineering. Many ground motion selection and modification procedures have been developed to select ground motions for a variety of objectives. This report focuses on the selection and scaling of single, horizontal components of ground motion for estimating seismic demand hazard curves of multistory frames at a given site. Worden et al. (2012) used a database of approximately 200,000 modified Mercalli intensity (MMI) observations of California earthquakes collected from U.S. Geological Survey reports, along with a comparable number of peak ground motion amplitudes from California seismic networks, to develop probabilistic relationships between MMI and peak ground velocity (PGV), PGA, and 0.3-s, 1-s, and 3-s 5% damped pseudo-spectral acceleration. After associating each ground motion observation with an MMI computed from all the seismic responses within 2 kilometers of the observation, a joint probability distribution between MMI and ground motion was derived. A reversible relationship was then derived between MMI and each ground motion parameter by using a total least squares regression to fit a bilinear function to the median of the stacked probability distributions. Among the relationships, the fit-to-peak ground velocity has the smallest errors, although linear combinations of PGA and PGV give nominally better results. The magnitude and distance terms also reduce the overall residuals and are justifiable on an information theoretical basis.

Literature Review and Synthesis 17 Another approach to developing the appropriate seismic hazard comes out of Europe. Delavaud et al. (2012) presented a strategy to build a logic tree for ground motion prediction in European countries. Ground motion prediction equations and weights have been determined so that the logic tree captures epistemic uncertainty in ground motion prediction for six different tectonic regions in Europe. This includes selecting candidate GMPEs and simultaneously running them through a panel of six experts to generate independent logic trees and rank the GMPEs on available test data. The collaboration of this information is used to set a weight to the GMPEs and create a consensus logic tree. This output then is run through a sensitivity analysis of the proposed weights on the seismic hazard before setting a final logic tree for the GMPEs. Tehrani and Mitchell (2014) used updated seismic hazard maps for Montreal, Canada to develop a uniform hazard spectra for Site Class C and a seismic hazard curve to analyze bridges in the localized area. Kramer and Greenfield (2016) evaluated three case studies following the 2011 Tohoku earthquake to better understand and design for liquefaction. Existing case history databases are incomplete with respect to many conditions for which geotechnical engineers are often required to evaluate liquefaction potential. These include liquefaction at depth, liquefaction of relatively dense soils, and liquefaction of gravelly soils. Kramer and Greenfield’s investigation of the three case histories will add to the sparse existing data for those conditions, and their interpretations will aid in the validation and development of predictive procedures for liquefaction potential evaluation. Structural Analysis and Design Predicting the structural response to the earthquake ground motions is critical for the PBSD process. NCHRP Synthesis 440 outlined several analysis methods that can be used to accomplish this task. The multimodal linear dynamic procedures are outlined in AASHTO LRFD Bridge Design Specifications (AASHTO 2014) and AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO 2011), although the Guide Specifications also include the parameters for performing a model pushover analysis in addition to prescriptive detail practices to ensure energy-dissipating systems behave as intended and other elements are capacity-protected. Other methods of analysis may be better suited for PBSD, but the initial PBSD approach will likely follow the procedures of the AASHTO guide specifications, with multi-level hazards and performance expectations. Limited research and code development have been accomplished since NCHRP Synthesis 440, but one new analysis method, outlined in Babazadeh et al. (2015), includes a three-dimensional finite element model simulation that is used to efficiently predict intermediate damage limit states in a consistent manner, with the experimental observations extracted from the actual tested columns. Other recent articles of structural analysis identified areas of improvement in the current design methodology that may be beneficial to PBSD. Huff and Pezeshk (2016) compared the substitute structure method methodology for isolated bearings with the displacement-based design methodology for ordinary bridges and showed that these two methodologies vary in estimating inelastic displacements. Huff (2016a) identified issues that are generally simplified or ignored in current practice of predicting inelastic behavior of bridges during earthquakes, both on the capacity (in the section of the element type and geometric nonlinearities) and demand (issues related to viscous dampening levels) sides of the process. The current SGS methodology for nonlinear static procedures were compared in Hajihashemi et al. (2017) with recent methodologies for multimodal pushover procedures that take into account all significant modes of the structure and with modified equivalent linearization procedures developed for

18 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design FEMA-440 (FEMA 2005). All of these analysis articles identify areas of current discussion on how to improve the analytical procedures proposed in the SGS. NCHRP Synthesis 440 focused primarily on new analysis methods, but a recent increased focus, in both academia and industry, has to do with new materials and systems and their impacts on PBSD. The evolution of enhanced seismic performance has been wrapped into several research topics, such as accelerated bridge construction (ABC), novel columns, and PBSD. The following are several aspects, though not all-encompassing, which have been improved upon in the last 6 years or so. Improving Structural Analysis Through Better Material Data The analysis and performance of a bridge are controlled with material property parameters incorporated into the seismic analysis models, specifically for the push-over analysis method. AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO 2011) specifies the strain limits to use for ASTM A706 (Grade 60) and ASTM A615 Grade 60 reinforcement. These strain limits come from Caltrans study of 1,100 mill certificates for ASTM A706 Grade 60 in the mid-1990s for projects in Caltrans bridge construction. The results were reported as elongation—not strain—at peak stress, so select bar pull tests were performed to correlate elongation to strain at peak stress. This was assumed to be a conservative approach, though it has recently been validated with a new ASTM A706 Grade 80 study at North Carolina State University by Overby et al. (2015a), which showed Caltrans numbers, by comparison, for Grade 60 are reasonable and conservative. Overby et al. (2015b) developed stress strain parameters for ASTM A706 Grade 80 reinforcing steel. Approximately 800 tests were conducted on bars ranging from #4 to #18 from multiple heats from three producing mills. Statistical results were presented for elastic modulus, yield strain and stress, strain-hardening strain, strain at maximum stress, and ultimate stress. Research is currently under way at North Carolina State University that aims to identify strain limit states, plastic hinge lengths, and equivalent viscous damping models for bridge columns constructed from A706 Grade 80 reinforcing steel. Work is also under way at the University of California, San Diego, on applications of Grade 80 rebar for capacity-protected members such as bridge cap beams. Design Using New Materials and Systems Structural analysis and design are fundamentally about structural response to the earthquake ground motion and the analysis methods used to develop this relationship. The complexity of the analysis depends on the geometry of the structure and elements and the extent of inelastic behavior. This is coupled with the damage, or performance criteria but has been broken out for the purposes of this report and NCHRP Synthesis 440. Next generation bridge columns, often referred to as novel columns, are improving as a tool for engineers to control both the structural analysis, as the make-up of the material changes the inelastic behavior, and the element performance of bridges in higher seismic hazards. The energy-dissipating benefits of low damage materials—such as ultrahigh-performance concrete (UHPC), engineered cementi- tious composites (ECC), and shape memory alloy, fiber-reinforced polymer (FRP) wraps and tubes, elastomeric bearings, and post-tensioned strands or bars—can be utilized by engineers to improve seismic performance and life-cycle costs after a significant seismic event. Recent (Saiidi et al. 2017) studies tested various combinations of these materials to determine if there are columns that can be built with these materials that are equivalent to, or better than, conventional reinforced concrete columns (in terms of cost, complexity, and construction duration) but that improve seismic performance, provide greater ductility, reduce damage, and accommodate a quicker recovery time and reduce loss in both the bridge and the economic environment.

Literature Review and Synthesis 19 Accelerated bridge construction is also a fast-developing field in bridge engineering, with draft guide specifications for design and construction currently being developed for adop- tion by AASHTO for AASHTO LRFD Bridge Design Specifications (AASHTO 2014). ABC has economic impacts that go beyond seismic engineering, but research is focusing on details and connections for accelerated construction in higher seismic regions, moving two research paths forward at the same time. Tazarv and Saiidi (2014) incorporated ABC research with novel column research to evaluate combined novel column materials that can be constructed quickly. The research focused on the performance of materials and how to incorporate them into practice. Key mechanical properties of reinforcing SMA were defined as follows: • Observed yield strength (fyo) is the stress at the initiation of nonlinearity on the first cycle of loading to the upper plateau. • Austenite modulus (k1) is the average slope between 15% to 70% of fyo. • Post yield stiffness (k2) is the average slope of curve between 2.5% and 3.5% of strain on the upper plateau of the first cycle of loading to 6% strain. • Austenite yield strength (fy) is the stress at the intersection of line passing through origin with slope of k1 and line passing through stress at 3% strain with slope of k2. • Lower plateau inflection strength (fi) is the stress at the inflection point of lower plateau during unloading from the first cycle to 6% strain. • Lower plateau stress factor, β = 1 – (fi/fy). • Residual strain (eres) is the tensile strain after one cycle to 6% and unloading to 1 ksi (7 MPa). • Recoverable super-elastic strain (er) is maximum strain with at least 90% strain recovery capacity. Using the ASTM standard for tensile testing, er ≤ 6%. • Martensite modulus (k3) is the slope of the curve between 8% to 9% strain, subsequent to one cycle of loading to 6% strain, unloading to 1 ksi (7 MPa) and reloading to the ultimate stress. • Secondary post-yield stiffness ratio, α = k3/k1. • Ultimate strain (eu) is strain at failure. A graphical representation is shown in Figure 9, and minimum and expected mechanical properties are listed in Table 3. Other researchers, such as at the University of Washington, are currently testing grouted bars using conventional grouts and finding that these development lengths can be reduced greatly. However, it is the force transfer of the grouted duct to the reinforcing outside the duct that may Figure 9. NiTi SE SMA nonlinear model.

20 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design require additional length to adequately develop the energy-dissipating or capacity-protecting system that was intended by the designer for performance of the bridge in a high seismic event. Tazarv and Saiidi (2014) identified other material properties such as UHPC and ECC, shown in Tables 4 and 5, respectively. Tazarv and Saiidi (2014) also addressed grouted splice sleeve couplers, self-consolidating concrete (SCC), and other connection types that could be used in ABC and novel column configurations, testing these materials in the laboratory to see if various combinations produced a logical system to be carried forward in research, design, and implementation. Trono et al. (2015) studied a rocking post-tensioned hybrid fiber-reinforced concrete (HyFRC) bridge column that was designed to limit damage and residual drifts and that was tested dynamically under earthquake excitation. The column utilized post-tensioned strands, HyFRC, and a combination of unbonded and headed longitudinal reinforcement. There have been two projects related to the field of novel columns and ABC through the National Cooperative Highway Research Program. One project was NCHRP Project 12-101, which resulted in NCHRP Report 864, 2 volumes (Saiidi et al. 2017), and the other project was NCHRP Project 12-105, which resulted in NCHRP Research Report 935 (Saiidi et al. 2020). NCHRP Project 12-101 identified three novel column systems—specifically, SMA and ECC, ECC and FRP, and hybrid rocking column using post-tensioned strands and fiber-reinforced Parameter Tensile Compressive,ExpectedbExpectedbMinimuma Table 3. Minimum expected reinforcing NiTi SE SMA mechanical properties. Properties Range Poisson’s Ratio 0.2 Creep Coefficient* 0.2 to 0.8 Total Shrinkage** *Depends on curing conditions and age of loading. up to 900x10-6 Equation Compressive Strength (f'UHPC) f'UHPC 20 to 30 ksi, (140 to 200 MPa) Coefficient of Thermal Expansion (5.5 to 8.5)x10 -6/°F, (10 to 15)x10-6/°C Specific Creep* (0.04 to 0.3)x10 -6/psi, (6 to 45)x10-6/MPa A time-dependent equation for UHPC strength is available. Tensile Cracking Strength (ft,UHPC) ft,UHPC = 6.7 (psi) f'UHPCEUHPC = 49000 (psi) 0.9 to 1.5 ksi, (6 to 10 MPa) Modulus of Elasticity (EUHPC) 6000 to 10000 ksi, (40 to 70 GPa) **Combination of drying shrinkage and autogenous shrinkage and depends on curing method. Table 4. UHPC mechanical properties.

Literature Review and Synthesis 21 polymer confinement—and compared them to a conventional reinforced column. The research and properties of the material are provided; incorporating laboratory tests and calibration, design examples are created to help engineers understand how to use these advanced materials in a linear elastic seismic demand model and to determine performance using a pushover analysis. It is worth noting that ductility requirements do not accurately capture the perfor- mance capabilities of these novel columns, and drift ratio limits are being used instead, similar to the building industry. NCHRP Project 12-101 also provided evaluation criteria that can be evaluated and incorporated by AASHTO into a guide specification or into AASHTO Guide Specifications for LRFD Seismic Bridge Design (AASHTO 2011) directly. NCHRP Project 12-105 synthesized research, design codes, specifications, and contract language throughout all 50 states and combined the knowledge base and lessons learned for ABC into proposed guide specifications for both design and construction. This work focused on connections, and most of that information is related to seismic performance of ABC elements and systems. Earthquake resisting elements (ERE) and earthquake resisting systems (ERS) are specifically identified, defined, and prescribed for performance in AASHTO guide specifica- tions (AASHTO 2011) but only implicitly applied in AASHTO LRFD Bridge Design Specifications (AASHTO 2014). Since NCHRP Project 12-105 is applicable to both of these design resources, ERE and ERS are discussed in terms of how to apply performance to the force-based seismic design practice of AASHTO LRFD Bridge Design Specifications (AASHTO 2014). The proposed guide specification language also identifies when performance of materials have to be incor- porated into the design, say in higher seismic hazards, and when it is acceptable to apply ABC connections and detailing practices with prescriptive design methodologies. As the industry’s understanding of performance increases, the engineering industry is accepting the benefits that come from a more user-defined engineering practice that is implemented by identifying material properties; evaluating hazards and soil and structural responses; and verifying performance through strain limits, damage limits states, moment curvature, displacements, and ductility. These tools and advancements in ABC and novel column designs, including other material property performance and analytical methodologies, are allowing PBSD to advance in other areas, such as hazard prediction, loss prediction, and the owner decision-making process. Feng et al. (2014a) studied the application of fiber-based analysis to predict the nonlinear response of reinforced concrete bridge columns. Specifically considered were predictions of overall force-deformation hysteretic response and strain gradients in plastic hinge regions. The authors also discussed the relative merits of force-based and displacement-based fiber elements and proposed a technique for prediction of nonlinear strain distribution based on the modified compression field theory. Fulmer et al. (2013) developed a new steel bridge system that is based upon ABC techniques that employ an external socket to connect a circular steel pier to a cap beam through the use of grout and shear studs. The resulting system develops a plastic hinge in the pipe away from the column-to-cap interface. An advantage of the design is ease of construction, as no field welding Properties Range Flexural Strength 1.5 to 4.5 ksi (10 to 30 MPa) Modulus of Elasticity 2600 to 5000 ksi (18 to 34 GPa) Ultimate Tensile Strain 1 to 8% Ultimate Tensile Strength 0.6 to 1.7 ksi (4 to 12 MPa) First Crack Strength 0.4 to 1.0 ksi (3 to 7 MPa) Compressive Strength 3 to 14 ksi (20 to 95 MPa) Table 5. ECC mechanical properties.

22 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design is required: the two assemblies are placed together and the annular space between the column and cap filled with grout. Figure 10 shows the details of this connection, and Figure 11 shows a test of the system. Another system being investigated is isolation bearings or dampening devices. Xie and Zhiang (2016) investigated the effectiveness and optimal design of protective devices for the seismic protection of highway bridges. Fragility functions are first derived by probabilistic seismic demand analysis, repair cost ratios are then derived using a performance-based methodol- ogy, and the associated component failure probability. Subsequently, the researchers tried to identify the optimal design parameters of protective devices for six design cases with various combinations of isolation bearings and fluid dampers and discussed the outcomes. Damage mitigation through isolation and energy dissipation devices is continually improving based on research, development, and implementation in the field. Recent events within the State of Washington, Alaska, and other state agencies have shown that the benefits of these tools can be compromised if the intended performance cannot be sustained for the 75-year design life of the structure. Mackie and Stojadinovic (2015) outlined performance criteria for fabrica- tion and construction that need to be administered properly, and engineers should consider the effects of moisture, salts, or other corrosive environmental conditions that can affect the performance of the isolation or energy-dissipating system. Another constraint with these systems can be the proprietary nature that occurs as a specific isolation or energy-dissipating system is utilized to develop a specific performance expectation that can only be accomplished with the prescribed system. This proprietary nature of these systems can create issues for certain funding sources that require equal bidding opportunities and the project expense that can accompany a proprietary system. To address this type of design constraint, Illinois DOT has been developing an earthquake-resisting system (ERS) to leverage the displacement capacity available at typical bearings in order to provide seismic protection to substructures of typical bridges. LaFave et al. (2013a) identified the effects and design parameters, Source: Fulmer et al. (2013). 5" 4 at 5" O.C. A A A-A Connection Details 45° UT 100% 3 8" 12 Studs Spaced Around Cross Section 30°Typ. 15° Offset Studs Inside Pipe from Cap Beam CL HSS16x0.500 Pipe 24x0.500 2'-0"2 14 " 4 at 5" O.C. 212"-34 "Ø Shear Studs 1'-11" Pipe Stud Detail Grout Provided By and Placed by NCSU Figure 10. Grouted shear stud bridge system.

Literature Review and Synthesis 23 such as fuse capacity, shear response, and sliding response, which can be used to account for more standard bearing configurations in seismic analysis, especially lower seismic hazard regions. A variation on the use of bearings in order to improve seismic performance of a pier wall configuration was outlined in Bignell et al. (2006). Historically, pinned, rocking, and sliding bearings have been used with interior pier walls and steel girder superstructures. These bearing configurations were compared with replacement elastomeric bearing configurations and details for structural analysis techniques, damage limit states, and structural fragility, and performance through probability distributions were utilized as a PBSD process for determining solutions to seismic isolation and enhanced seismic performance. The foundation conditions, pier wall effects, bearing type, and even embankment effects to structural performance were included in this evaluation. Another approach to enhanced performance is modifications to foundation elements or increased understanding and modeling of soil–structure interaction, specifically where lateral spread or liquefaction design conditions make conventional bridge design and elements imprac- tical. One example of this is the seismic design and performance of bridges constructed with rocking foundations, as evaluated in Antonellis and Panagiotou (2013). This type of rocking goes beyond the loss of contact area currently allowed in the guide specifications. The applica- tion of columns supported on rocking foundations accommodates large deformations, while there is far less damage, and can re-center after large earthquakes. Another approach is to tie a tolerable displacement of an individual deep foundation element to a movement that would cause adverse performance, excessive maintenance issues, or functionality problems with the bridge structure. Roberts et al. (2011) established a performance-based soil–structure–interaction design approach for drilled shafts. Chiou and Tsai (2014) evaluated displacement ductility of an in-ground hinging of a fixed head pile. Assessment formulas were developed for the displacement ductility capacity of a fixed-head pile in cohesion-less soils. The parameters in the formulas included the sectional over-strength ratio and curvature ductility capacity, as well as a modification factor for consider- ing soil nonlinearity. The modification factor is a function of the displacement ratio of the pile’s ultimate displacement to the effective soil yield displacement, which is constructed through a number of numerical pushover analyses. Source: Fulmer et al. (2013). Figure 11. Photograph of completed system before seismic testing showing hinge locations.

24 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Damage Analysis As stated in NCHRP Synthesis 440, it is a fundamental need for the PBSD methodology to determine the type of damage and the likelihood that such damage will occur in the particular components of the structural system. This determination is of vital importance, as the damage sustained by a structure (and its nonstructural components) is directly relatable to the use or loss of a system after an earthquake. Therefore, there is a need to be able to reliably link structural and nonstructural response (internal forces, deformations, accelerations, and displacements) to damage. This is the realm of damage analyses, where damage is defined as discrete observable damage states (e.g., yield, spalling, longitudinal bar buckling, and bar fracture). Although the primary focus of the discussions is on structural components, similar considerations must be made for nonstructural components as well. NCHRP Synthesis 440 outlined an initial discussion on types of structural damage observed during historic earthquakes and laboratory experiments, prefaced the methods that have been developed to predict damage, identified structural details and concepts that could be used to reduce damage even in strong ground shaking, and reviewed post-event inspection tools. The new materials discussed in previous sections also apply to this discussion but are not repeated herein. Accurate damage prediction relies upon accurate definitions of performance limit states at the material level (i.e., strain limits) and the corresponding relationship between strain and displacement. Examples of recent research follow. Research by Feng et al. (2014b, 2014c) used finite element analysis validated by experimental test results to develop a model for predicting the tension strain corresponding to bar buckling. The model considers the impact of loading history on the boundary conditions of longitudinal bar restraint provided by the transverse steel. Goodnight et al. (2016a) identified strain limits to initiate bar buckling based on experimental results from 30 column tests (Equation 2). Following additional bidirectional tests on 12 columns, Equation 2 was revised to Equation 3. In addition, strain limit state equations were proposed for the compression strain in concrete to cause spiral yielding (Goodnight et al. 2017a). Goodnight et al. (2016b) also developed a new plastic hinge length model based on the data collected during those tests, which accounts for the actual curvature distribution in RC bridge columns. The revised model separates the strain penetration component from the flexural component while also recognizing that the hinge length for compression is smaller than that for tension. Brown et al. (2015) developed strain limit state (Equation 4) (tube wall local buckling) and equivalent viscous damping equations for reinforced concrete filled steel tubes (RCFSTs). The recommendations of the authors were based upon reversed cyclic tests of 12 RCFSTs of variable D/t (diameter to thickness) ratios. 0.03 700 0.1 (2)bucklingbar f E P f A s s yhe s ce g ε = + ρ − ′ 0.032 790 0.14 (3)bucklingbar f E P f A s s yhe s ce g ε = + ρ − ′ 0.021 9100 (4)tension buckling D t yε = − ≥ ε

Literature Review and Synthesis 25 where rs = reinforcement ratio, fyhe = expected yield strength of the steel tube (ksi), Es = elastic modulus of steel (ksi), P = axial load (kip), f ′ce = expected concrete strength (ksi), Ag = gross area of concrete (in.2), D = diameter of tube (in.), t = thickness of tube (in.), and ey = yield strain for steel (in./in.). Loss Analysis The PBSD combines the seismic hazard, structural, and damage analysis into a performance matrix that can be estimated into a loss metric. There are many loss metrics that can be used by, and that are important to, stakeholders and decision makers (discussed in detail in NCHRP Synthesis 440), but all these metrics can be boiled down to three main categories: deaths, dollars, and downtime. Bertero (2014) discussed earthquake lessons, in terms of loss, to be considered in both design and construction of buildings. At the beginning of 2010, two large earthquakes struck the Americas. The January 12, 2010, Haiti earthquake with a magnitude 7.0 produced about 300,000 deaths (second by the number of fatalities in world history after the 1556 Shaanxi, China earthquake). A month later, the February 27, 2010, Maule Chilean earthquake with a magnitude 8.8 (an energy release 500 times bigger than that from the Haiti earthquake) produced 500 deaths, most due to the resulting tsunami. However, the Chilean earthquake caused more than $30 billion of direct damage, left dozens of hospitals and thousands of schools nonoperational, and caused a general blackout for several hours, as well as the loss of service of essential communications facilities, crucial to take control of the chaotic after-earthquake situ- ation. Bertero (2014) compared the severity of both earthquakes and comments on their effects to life and the economy of the affected countries, as well as the features of the seismic codes or the absence of codes. An example of risk analysis with PBSD is utilized in Bensi et al. (2011), with the development of a Bayesian network (BN) methodology for performing infrastructure seismic risk assessment and providing decision support with an emphasis on immediate post-earthquake applications. A BN is a probabilistic graphical model that represents a set of random variables and their probabilistic dependencies. The proposed methodology consists of four major components: (1) a seismic demand model of ground motion intensity as a spatially distributed random field, accounting for multiple sources and including finite fault rupture and directivity effects; (2) a model for seismic performance of point-site and distributed components; (3) models of system performance as a function of component states; and (4) models of post-earthquake decision making for inspection and operation or shutdown of components. The use of the term Bayesian to describe this approach comes from the well-known Bayes rule, attributed to the 18th-century mathematician and philosopher Thomas Bayes: A B AB B B A B A( ) ( )( ) ( ) ( ) ( )= =Pr Pr Pr Pr Pr Pr (5) Pr(AB) is the probability of joint occurrence of Events A and B; Pr(A) is the marginal probability of Event A; Pr(A|B) is the conditional probability of Event A, given that Event B

26 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design has occurred; and Pr(B) is the marginal probability of Event B. The quantity Pr(B | A) is known as the likelihood of the observed Event B. Note that the probability of Event A appears on both sides of Equation 5. The Bayes rule describes how the probability of Event A changes given information gained about the occurrence of Event B. For discrete nodes, a conditional probability table is attached to each node that provides the conditional probability mass function (PMF) of the random variable represented by the node, given each of the mutually exclusive combinations of the states of its parents. For nodes without parents (e.g., X1 and X2 in Figure 12), known as root nodes, a marginal probability table is assigned. The joint PMF of all random variables X in the BN is constructed as the product of the conditional PMFs: (6) 1 p x p x Pa xi ii n∏( ) ( )( )= = Bensi et al. (2011) goes on to introduce BN models further and discusses how to incorporate BN-based seismic demand models into bridge design. The BN methodology is applied to modeling of random fields, construction of an approximate transformation matrix, and numer- ical investigation of approximation methods, including a discussion on the effect of correlation approximations on system reliability. Modeling component performance with BNs to capture seismic fragility of point-site components and distributed components, as well as modeling system performance of BNs with both qualitative and conventional methods, is explained. This reference goes on to identify efficient minimal link set (MLS), minimal cut set (MCS) formulations, optimal ordering of efficient MLS and MCS formulations, and heuristic augmen- tation that can be utilized with the BN methodology. Bensi et al. (2011) continues the PBSD process by addressing the owner decision-making process (see more discussion later in the report) and how to incorporate this model into that process. Two example problems are provided utilizing this methodology, including a California high-speed rail system that incorporates the bridge modeling into the example. Similarly, in Tehrani and Mitchell (2014), the seismic performance of 15 continuous four- span bridges with different arrangements of column heights and diameters was studied using incremental dynamic analysis (IDA). These bridges were designed using the Canadian Highway Bridge Design Code provisions (CSA 2006). The IDA procedure has been adopted by some guidelines to determine the seismic performance, collapse capacity, and fragility of buildings. Similar concepts can be used for the seismic assessment of bridges. Fragility curves can be devel- oped using the IDA results to predict the conditional probability that a certain damage state is exceeded at a given intensity measure value. Assuming that the IDA data are lognormally distributed, it is possible to develop the fragility curves at collapse (or any other damage state) by computing only the median collapse capacity and the logarithmic standard deviation of the IDA results for any given damage state. The fragility curves can then be analytically computed using Equation 7 as follows: ln ln (7)50% TOT P failure S x x S a a C( )( ) ( )= = Φ − β     where function F = cumulative normal distribution function, SCa 50% = median capacity determined from the IDA, and βTOT = total uncertainty caused by record-to-record variability, design requirements, test data, and structural modeling. Figure 12. A simple BN.

Literature Review and Synthesis 27 The seismic risk associated with exceeding different damage states in the columns, includ- ing yielding, cover spalling, bar buckling, and structural collapse (i.e., dynamic instability) was predicted. Some simplified equations were derived for Montreal, Quebec, Canada, to estimate the mean annual probability of exceeding different damage states in the columns using the IDA results. Repair and retrofit procedures are linked to loss predictions, as outlined in the FHWA’s retro- fitting manual (Buckle et al. 2006). Several chapters/articles address analysis, methodologies, effects, analytical tools, and costs for retrofit and repairs to mitigate damage or return a structure to a serviceable condition. Zimmerman et al. (2013) is one example, in which numerical techniques and seismic retrofit solutions for shear-critical reinforced concrete columns was investigated, utilizing test data of a reinforced concrete column with widely spaced transverse reinforcement. The study focused on the analysis method of nonlinear trusses and the retrofit option known as supplemental gravity columns, which is an example of how loss prediction and the analysis process are linked and should be iterated through PBSD. Organization-Specific Criteria for Bridges and Project-Specific Criteria NCHRP Synthesis 440 has two sections of criteria: organization-specific criteria for bridges and project-specific criteria. New information for both of these sections since NCHRP Synthesis 440 published is combined. The California DOT (Caltrans) Caltrans is currently updating their Seismic Design Criteria (SDC) to specify requirements to meet the performance goals for newly designed Ordinary Standard and Recovery Standard con- crete bridges. Nonstandard bridges require Project-Specific Seismic Design Criteria, in addition to the SDC, to address their nonstandard features. For both standard and nonstandard bridges, Caltrans is also categorizing their inventory in terms of Ordinary Bridges, Recovery Bridges, and Important Bridges. Some states have had issues with terms like Important or Essential, as a bridge is considered important to those that utilize each bridge. Caltrans is using these terms to correlate with loss analysis of an owner’s infrastructure and the time to reopen the bridge to support lifeline and recovery corridors. The bridge performance is also evaluated using a dual-seismic hazard; for Caltrans SDC they are listed as a Safety Evaluation Earthquake (SEE) for Ordinary Bridges. Both SEE and Functional Evaluation Earthquake (FEE) for Recovery Bridges are summarized in Table 6. Caltrans SDC revisions will also provide updates to the design parameters in Chapter 3 of the SDC and updates to both the analysis methods and displacement ductility demand values in Chapter 4 of the SDC. The adjustments to the displacement ductility demand values are revised to limit the bridge displacements beyond the initial yielding point of the ERE, specifically if a recovery standard bridge is being designed. The revisions to their SDC is an example of how PBSD is being gradually introduced as a better method of dealing with the hazards, soil–structure interaction, analysis tools, methodologies, material properties, damage states, performance, and loss. Similar revisions are being made to Seismic Design Specifications of Highway Bridges, as detailed in Japan Road Association (JRA) revisions in 2012. A synopsis of the revisions is provided in Kuwabara et al. (2013). The JRA specifications apply to Japanese road bridges and consist of five parts: Part I, Common; Part II, Steel Bridges; Part III, Concrete Bridges; Part IV, Substruc- tures; and Part V, Seismic Design. The revisions are based on improvements in terms of safety,

28 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design serviceability, and durability of bridges. Based on those lessons, design earthquake ground motions corresponding to the subduction-type earthquake were revised, and the requirements for easy and secure maintenance (inspection and repair works) for the bridges were clearly specified. JRA has clarified their performance of ERE conventionally reinforced columns for a dual-level (SPL 2 and SPL 3) seismic performance evaluation, as summarized in Table 7. The JRA 2012 revisions also address connection failures between reinforced concrete steel piles and the pile-supported spread footing to improve structural detailing and performance at the head of the piles. This is similar to research performed by the University of Washington, see Stephens et al. (2015) and Stephens et al. (2016) for both Caltrans and Washington State DOT, respectively, to evaluate capacity protecting this region and even considering the development of plastic hinges at these locations for combined hazard events or large lateral spreading and liquefaction occurrences. Caltrans also funded a study by Saini and Saiidi (2014) to address probabilistic seismic design of bridge columns using a probabilistic damage control approach and reliability analysis. Source: Caltrans. BRIDGE CATEGORY SEISMIC HAZARD EVALUATION LEVEL POST EARTHQUAKE DAMAGE STATE EXPECTED POST EARTHQUAKE SERVICE LEVEL Table 6. Caltrans draft proposed seismic design bridge performance criteria. SPL2 SPL3 Note: SPL1: Fully operational is required. Limit state of bridge is serviceability limit state. Negligible structural damage and nonstructural damage are allowed. Table 7. Seismic performance of bridge and limit states of conventionally reinforced concrete bridge column.

Literature Review and Synthesis 29 The probabilistic damage control approach uses the extent of lateral displacement nonlinearity defined by Damage Index (DI) to measure the performance of bridge columns. DI is a measure of damage from the lower measure of zero damage to the ultimate measure of a collapse mecha- nism for an element that has been subjected to base excitations. The performance objective was defined based on predefined apparent Damage States (DS), and the DS were correlated to DIs based on a previous study at the University of Nevada, Reno (Figure 13) (Vosooghi and Saiidi 2010). A statistical analysis of the demand damage index (DIL) was performed to develop fragility curves (load model) and to determine the reliability index for each DS. The results of the reliability analyses were analyzed, and a direct probabilistic damage control approach was developed to calibrate design DI to obtain a desired reliability index against failure. The calculated reliability indices and fragility curves showed that the proposed method could be effectively used in seismic design of new bridges, as well as in seismic assessment of existing bridges. The DS and DI are summarized with performance levels defined by Caltrans in Table 8, which shows the correlation between DS and DI. Figure 14 shows a fragility curve using lognormal distribution. Figure 15 shows both the fragility curves (upper two graphs) and reliability indices (lower two graphs) for four column bents (FCBs), with 4-foot diameter columns that are 30 feet in length in Site D for both the 1000 year and 2500 year seismic events. Note: O-ST = ordinary standard bridge, O-NST = ordinary nonstandard bridge, Rec. = recovery bridge, Imp. = important bridge, and NA = not applicable. Damage State (DS) Service to Public Service to Emergency Emergency Repair Design Damage Index (DI) Earthquake Levels (Years) Table 8. Design performance levels. DI P (D I { D S) Figure 13. Correlation between DS and DI.

30 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Figure 14. Fragility curve. 100% 80% 60% 40% 20% 0% 0.00 0.20 0.40 0.60 0.80 1.00 P (D I L ) DIL 4.0 3.0 2.0 1.0 0.0 R el ia bi lit y In de x | D S DS3 DS4 DS5 DS6 Damage State (DS) 6.0 5.0 4.0 3.0 2.0 1.0 0.0 R el ia bi lit y In de x | D S DS3 DS4 DS5 DS6 Damage State (DS) (a) (b) (d)(c) 0.00 0.20 0.40 0.60 0.80 1.00 DIL 100% 80% 60% 40% 20% 0% P (D I L ) Figure 15. Fragility curves and reliability indices for FCBs with 4-foot columns in Site D. The Oregon DOT The Oregon DOT is developing a global plan for addressing resiliency in order to improve recovery for the next Cascadia Earthquake and Tsunami, using PBSD in terms of applying applicable hazards, identifying critical services, developing a comprehensive assessment of structures and systems, and updating public policies. The resilience goals are similar to those discussed at the beginning of this chapter, with the following statement: Oregon citizens will not only be protected from life-threatening physical harm, but because of risk reduction measures and pre-disaster planning, communities will recover more quickly and with less continuing vulnerability following a Cascadia subduction zone earthquake and tsunami.

Literature Review and Synthesis 31 Research has shown that the next great (magnitude 9.0) Cascadia subduction zone earth- quake is pending, as shown in Figure 16. This comparison of historical subduction zone earthquakes in northern California, Oregon, and Washington covers 10000 years of seismic history. The evidence of a pending event has made decision makers and the public take notice and put forth resources to develop strategies revolving around PBSD. Oregon’s performance-based features are modified from NCHRP Synthesis 440 to account for a third hazard condition: Cascadia Subduction Zone Earthquake (CSZE) in Oregon DOT’s Bridge Design and Drafting Manual—Section 1, Design (Oregon DOT 2016a; see also Oregon DOT 2016b). Design of new bridges on and west of US 97 references two levels of perfor- mance criteria: life safety and operational. Design of new bridges east of US 97 requires life safety criteria only. Seismic design criteria for life safety and operational criteria are described as follows. • “Life Safety” Criteria: Design all bridges for a 1,000-year return period earthquake (7 percent prob- ability of exceedance in 75 years) to meet the “Life Safety” criteria using the 2014 USGS Hazard Maps. The probabilistic hazard maps for an average return period of 1,000 years and 500 years are available at ODOT Bridge Section website, but not available on USGS website. To satisfy the “Life Safety” criteria, use Response Modification Factors from LRFD Table 3.10.7.1-1 using an importance category of “other.” • “Operational” Criteria: Design all bridges on and west of US 97 to remain “Operational” after a full rupture of Cascadia Subduction Zone Earthquake (CSZE). The full-rupture CSZE hazard maps are available at the ODOT Bridge Section website. To satisfy the “Operational” criteria, use Response Modification Factors from LRFD Table 3.10.7.1-1 using an importance category of “essential.” When requested in writing by a local agency, the “Operational” criteria for local bridges may be waived. The CSZE is a deterministic event, and a deterministic design response spectrum must be generated. To allow for consistency and efficiency in design for the CSZE, an application for generating the design response spectra has been developed by Portland State University (Nako et al. 2009). AASHTO guide specifications values for Table 3.4.2.3-1 are modified into two tables for (1) values of Site Factor, Fpga, at zero-period on the acceleration spectrum and (2) values of Site Factor, Fa, for short-period range of acceleration spectrum. Table 3.4.2.3-2 is replaced with values of Site Factor, Fv, for long-period range of acceleration spectrum. For seismic retrofit projects, the lower level ground motion is modified to be the CSZE with full rupture, as seen in Table 9. Performance levels, including performance level zero (PL0), are specified based on bridge importance and the anticipated service life (ASL) category required. Source: OSSPAC (2013). Figure 16. Cascadia earthquake timeline.

32 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design The South Carolina DOT South Carolina Department of Transportation (South Carolina DOT) has updated its geo- technical design manual (South Carolina DOT 2019). Chapters 12, 13, and 14 for geo technical seismic analysis, hazard, and design, respectively, have been updated to current practices and research, including incorporation of PBSD hazard prediction. South Carolina DOT is also updating their site coefficients to be more appropriate for South Carolina’s geologic and seismic conditions; see Andrus et al. (2014). Note that with the revisions, South Carolina DOT issued a design memorandum in November 2015 that revised the substructure unit quantitative damage criteria (maximum ductility demand) table (Table 7.1 of the SCDOT Seismic Design Specifications for Highway Bridges). See Table 10. The Utah DOT The Utah DOT and Brigham Young University (see Franke et al. 2014a, 2014b, 2015a, 2015b, 2015c, 2016) are researching the ability for engineers to apply the benefits of the full performance- based probabilistic earthquake analysis without requiring specialized software, training, or education. There is an emphasis on differences between deterministic and performance-based procedures for assessing liquefaction hazards and how the output can vary significantly with these two methodologies, especially in areas of low seismicity. Guidance is provided regarding when to use each of the two methodologies and how to bind the analysis effort. Additionally, a simplified performance-based procedure for assessment of liquefaction triggering using liquefaction loading maps was developed with this research. The components of this tool, as well as step-by-step procedures for the liquefaction initiation and lateral spread displacement models, are provided. The tool incorporates the simplified performance-based procedures determined with this research. National Highway Institute Marsh et al. (2014) referenced a manual for the National Highway Institute’s training course for engineers to understand displacement-based LRFD seismic analysis and design of bridges, which is offered through state agencies and open to industry engineers and geotechnical engi- neers. This course helps designers understand the principles behind both force-based AASHTO (AASHTO 2014) and displacement-based AASHTO (AASHTO 2011) methodologies, including a deeper understanding of what performance means in a seismic event. Other similar courses are also being offered to industry and are improving the understanding of practicing engineers. Federal Emergency Management Agency The Federal Emergency Management Agency (FEMA) has developed a series of design guidelines for seismic performance assessment of buildings and three of the five documents EARTHQUAKE GROUND MOTION BRIDGE IMPORTANCE and SERVICE LIFE CATEGORY Table 9. Modifications to minimum performance levels for retrofitted bridges.

Literature Review and Synthesis 33 are referenced in FEMA (2012a, 2012b, 2012c). A step-by-step methodology and explanation of implementation are provided for an intensity-based assessment and for a time-based assess- ment. The process of identifying and developing appropriate fragility curves is demonstrated. A software program called Performance Assessment Calculation Tool has also been developed with a user manual that is included in the FEMA documents to help engineers apply PBSD to the building industry. Japan Road Association The Japan Road Association (JRA) Design Specifications have been revised based on the performance-based design code concept in response to the international harmonization of design codes and the flexible employment of new structures and new construction methods. Figure 17 shows the code structure for seismic design using the JRA Design Specifications. The performance matrix is based on a two-level ground motion (Earthquakes 1 and 2), with the first one based on an interpolate-type earthquake and magnitude of around 8, and the second one with a magnitude of around 7 with a short distance to the structure. Kuwabara et al. (2013) outlined the incremental revisions from the JRA Design Specif i- cations between 2002 and 2012. These revisions include, but are not limited to, the ductility design method of reinforced concrete bridges, plastic hinge length equation, evaluation of hollow columns, and the introduction of high-strength steel reinforcement. Following the 2016 earthquake in Kumamoto, Japan, a new version of the JRA Design Specifications is in the works. Note: Analysis for FEE is not required for OC III bridges. Source: South Carolina DOT (2015). Design Earthquake Operational Classification (OC)Bridge Systems Table 10. South Carolina DOT substructure unit quantitative damage criteria (maximum ductility demand ld).

34 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design Identification of Knowledge Gaps The resources to develop guide specifications for PBSD are improving with examples such as the upcoming Seismic Design Criteria, Version 2 from Caltrans, which will address aspects of PBSD and the building industry’s efforts to develop practices in PBSD and tools for engineers and owners to collaborate on solutions based on performance criteria and expectations. There is still a perception that the bridge industry could better predict likely performance in large, damaging earthquakes than is being done at the present, and there are still gaps in that knowledge base that need to be closed. Most of the knowledge gaps listed in Marsh and Stringer (2013) are still applicable today; see Table 11. The technology readiness levels represent what has been developed and used; what research is done, ongoing, and being discussed; and what only exists in concept. Knowledge gaps certainly exist in all facets of PBSD; however, other key knowledge gaps beyond those listed in NCHRP Synthesis 440 (Marsh and Stringer 2013) that should be closed in order to improve the implementation of PBSD are covered. Objectives of Codes Mandated Specifications Overall Goals Functional Requirements (Basic Requirements) Performance Requirement Level Verification Methods and Acceptable Solutions Can be Modified or May be Selected with Necessary Verifications Importance, Loads, Design Ground Motion, Limit States Principles of Performance Verification Verifications of Seismic Performances (Static and Dynamic Verifications) Evaluation of Limit States of Members (RC and Steel Columns, Bearings, Foundations and Superstructure) Unseating Prevention Systems Principles of Seismic Design Figure 17. Code structure for seismic design using JRA design specifications. TRL Description 0-25 25-50 50-75 75-100 1 PBSD concept exists 2 Seismic hazard deployable 3 Structural analysis deployable 4 Damage analysis deployable 5 Loss analysis deployable 6 Owners willing and skilled in PBSD 7 Design guidelines 8 Demonstration projects 9 Proven effectiveness in earthquake Technology Readiness Level (TRL) % of Development Complete Table 11. Technology readiness levels for PBSD.

Literature Review and Synthesis 35 Gaps related to structural analysis can include minimum and expected properties for reinforcing greater than Grade 80, stainless steel, and other materials that can improve serviceability and in some conditions performance. Oregon DOT has been using stainless steel in their bridges located along the coastline and other highly corrosive environments to extend the service life of the bridge; however, many of these locations are also prone to large CSZE and the use of these materials in earthquake resisting elements is still being developed. In the State of Washington’s resiliency plan, outlined in Washington State Emergency Management Council–Seismic Safety Committee (2012), what is missing is a link between damage levels and return to service. This is a knowledge gap given what we know structurally and what this report is suggesting as a desired goal for post-earthquake recovery. Gaps related to decision makers can include bridge collapse. It is not intended that the PBSD guide specifications will address tsunami events, but the JRA specifications do address tsunami as well as landslide effects. Figures 18 and 19 are examples of these other types of failure systems and show the collapse of bridges caused by effects other than ground motion (Kuwabara et al. 2013). The decision to combine these types of effects with a seismic hazard, even combining liquefaction, down drag, and lateral spreading effects, needs additional clarification and is currently left up to the owner to assess implications of probability, safety, and cost ramifications. Liang and Lee (2013) summarized that in order to update the extreme event design limit states in the AASHTO 2014, combinations of all nonextreme and extreme loads need to be formulated on the same probability-based platform. Accounting for more than one-time variable load creates a complex situation, in which all of the possible load combinations, even many that are not needed for the purpose of bridge design, have to be determined. A formulation of a criterion to determine if a specific term is necessary to be included or rejected is described, and a comparison of the value of a given failure probability to the total pre-set permissible design failure probability can be chosen as this criterion. Figure 18. Collapse of bridge due to landslide. (Note: Reprinted courtesy of the National Institute of Standards and Technology, U.S. Department of Commerce. Not copyrightable in the United States). Source: Kuwabara et al. (2013).

36 Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design While the seismic hazard definition was once thought to be relatively well understood, there is a growing knowledge gap related to the effect of rotation angle on intensity of ground motions and how the use of a geometric mean of the motions, or other methods of including the effect of rotation angle (RotDxx), should be incorporated into seismic design. This issue is not specific to PBSD; like all seismic design methods, PBSD is reliant on a full understanding of the hazard definition for proper implementation. The knowledge gaps identified in NCHRP Synthesis 440 are still applicable. Many of these knowledge gaps will become evident to both engineers and decision makers as the PBSD guidelines are developed. Overall, the baseline information to develop PBSD guide specifica- tions are in place. Industry’s end goal of understanding the relationship between risk-based decision making and design decisions and methodologies to meet performance goals is going to be an iterative process. Figure 19. Collapse of bridge due to tsunami. (Note: Reprinted courtesy of the National Institute of Standards and Technology, U.S. Department of Commerce. Not copyrightable in the United States). Source: Kuwabara et al. (2013).

Performance-based seismic design (PBSD) for infrastructure in the United States is a developing field, with new research, design, and repair technologies; definitions; and methodologies being advanced every year.

The TRB National Cooperative Highway Research Program's NCHRP Research Report 949: Proposed AASHTO Guidelines for Performance-Based Seismic Bridge Design presents a methodology to analyze and determine the seismic capacity requirements of bridge elements expressed in terms of service and damage levels of bridges under a seismic hazard. The methodology is presented as proposed AASHTO guidelines for performance-based seismic bridge design with ground motion maps and detailed design examples illustrating the application of the proposed guidelines and maps.

Supplemental materials to the report include an Appendix A - SDOF Column Investigation Sample Calculations and Results and Appendix B - Hazard Comparison.

READ FREE ONLINE

Welcome to OpenBook!

You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

Do you want to take a quick tour of the OpenBook's features?

Show this book's table of contents , where you can jump to any chapter by name.

...or use these buttons to go back to the previous chapter or skip to the next one.

Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

To search the entire text of this book, type in your search term here and press Enter .

Share a link to this book page on your preferred social network or via email.

View our suggested citation for this chapter.

Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

Get Email Updates

Do you enjoy reading reports from the Academies online for free ? Sign up for email notifications and we'll let you know about new publications in your areas of interest when they're released.

• Literature Search

Q: How to outline the subtopics of review related literature?

Asked by Simonnette Saidoreg on 03 Nov, 2021

A review of related literature (RRL) puts your research in the context of what is currently known about the topic. Accordingly, it is a good way to highlight the knowledge gaps and what your study offers in terms of novelty and significance. Your question on outlining the subtopics is a pertinent one. However, outlining subtopics would heavily rely on the specific topic you are writing on. Without knowing that, we cannot clearly delineate the subtopics and their position in the text. However, we will try to provide hints that will help you choose and organize them optimally.

The opening paragraphs should provide an informative background, perhaps with a historical perspective, if applicable. Then, you should streamline the broad topic by narrowing the focus on the basis of various parameters.

Depending on the topic, you might want to choose a chronological organization or a thematic one. The former would require you to discuss the developments in the field from old to new. Meanwhile, a methodological review deals with research, data collection, and data analysis techniques. The subtopics in a methodological review would be specific methods/approaches followed in different studies, each with their pros and cons. An RRL organized by theme would have subheadings on various key concepts. One way to group the literature might be by region: global, regional, and national-level studies. Another way to group topics might be according to study findings, i.e., papers with similar results could be grouped together, and conflicting results could appear separately.

Note that each subtopic might have further subsections and sub-subsections. Moreover, managing references can be quite daunting. Make sure you use literature discovery apps ( R Discovery ) or reference managers like Mendeley. Questions similar to yours have been answered here:

• How do I do a review of related literature (RRL)?
• What would be the review of related literature (RRL) for my topic?

Hope this answers your question. All the best for your study

Answered by Editage Insights on 30 Nov, 2021

• Upvote this Answer

This content belongs to the Conducting Research Stage

Confirm that you would also like to sign up for free personalized email coaching for this stage.

Trending Searches

• Statement of the problem
• Background of study
• Scope of the study
• Types of qualitative research
• Rationale of the study
• Concept paper
• Literature review
• Introduction in research
• Under "Editor Evaluation"
• Ethics in research

Recent Searches

• Review paper
• Responding to reviewer comments
• Predatory publishers
• Scope and delimitations
• Open access
• Plagiarism in research
• Journal selection tips
• Editor assigned
• Types of articles
• "Reject and Resubmit" status
• Decision in process
• Conflict of interest

International Journal of Science and Research (IJSR) Call for Papers | Fully Refereed | Open Access | Double Blind Peer Reviewed

ISSN: 2319-7064

What is RRL in Research Paper?

RRL in a research paper usually refers to " Related Research Literature " or "Review of Related Literature". It is a section in a research paper that discusses the relevant studies, theories, and concepts that have been published in academic journals, books, or other sources that are related to the research topic.

The purpose of the RRL section is to provide a comprehensive understanding of the existing knowledge on the topic and to highlight the gaps in the literature that the current study aims to address. It also helps to establish the context of the research and to support the significance and relevance of the study.

The RRL section typically includes a summary and critique of the previous studies, identification of the similarities and differences between the previous studies and the current research, and a discussion of the theoretical frameworks or models that underlie the research. The sources cited in this section are used to build the theoretical foundation of the study, and they provide a basis for the formulation of the research questions or hypotheses.

Managing Editor , International Journal of Science and Research (IJSR)

www.ijsr.net

Numbers, Facts and Trends Shaping Your World

Read our research on:

Full Topic List

Regions & Countries

• Publications
• Our Methods
• Short Reads
• Tools & Resources

Read Our Research On:

What Are Americans’ Top Foreign Policy Priorities?

Protecting the u.s. from terrorism and reducing the flow of illegal drugs are top issues overall, but democrats and republicans have very different priorities, table of contents.

• Differences by partisanship
• Differences by age
• Acknowledgments
• The American Trends Panel survey methodology

Pew Research Center conducted this analysis to better understand Americans’ long-range foreign policy priorities. For this analysis, we surveyed 3,600 U.S. adults from April 1 to April 7, 2024. Everyone who took part in this survey is a member of the Center’s American Trends Panel (ATP), an online survey panel that is recruited through national, random sampling of residential addresses. This way nearly all U.S. adults have a chance of selection. The survey is weighted to be representative of the U.S. adult population by gender, race, ethnicity, partisan affiliation, education and other categories. Read more about the ATP’s methodology .

Here are the questions used for this analysis, along with responses, and its methodology .

Americans have a lot on their plates in 2024, including an important election to determine who will remain or become again president. But the world does not stop for a U.S. election, and multiple conflicts around the world as well as other issues of global prominence continue to concern Americans.

When asked to prioritize the long-range foreign policy goals of the United States, the majority of Americans say preventing terrorist attacks (73%), keeping illegal drugs out of the country (64%) and preventing the spread of weapons of mass destruction (63%) are top priorities. Over half of Americans also see maintaining the U.S. military advantage over other countries (53%) and preventing the spread of infectious diseases (52%) as primary foreign policy responsibilities.

About half of Americans say limiting the power and influence of Russia and China are top priorities. A recent annual threat assessment from the U.S. intelligence community focused heavily on those countries’ strengthening military relationship and their ability to shape the global narrative against U.S. interests.

Fewer than half of Americans say dealing with global climate change (44%) and getting other countries to assume more of the costs of maintaining world order (42%) are top priorities. The partisan gaps on these two issues are quite large:

• 70% of Democrats and Democratic-leaning independents say climate change should be a top priority, while 15% of Republicans and Republican leaners say this.
• 54% of Republicans say getting other countries to assume more of the costs of maintaining world order should be a top priority, compared with 33% of Democrats.

About four-in-ten Americans see limiting the power and influence of North Korea and Iran as top priorities. (The survey was conducted before Iran’s large-scale missile attack on Israel on April 13.) And about a third say the same about the U.S. being a leader in artificial intelligence, a technology that governments around the world are increasingly concerned about .

When it comes to goals that focus on international engagement, like strengthening the United Nations and NATO or finding a solution to the Israeli-Palestinian conflict, fewer than a third of Americans mark these as top foreign policy priorities.

Related: Fewer Americans view the United Nations favorably than in 2023

Only about a quarter of Americans prioritize promoting human rights in other countries, leading other countries in space exploration and reducing military commitments overseas. And similar shares say supporting Ukraine (23%) and Israel (22%) are top issues.

At the bottom of this list of foreign policy priorities are promoting global democracy ( a major policy push from the Biden administration ) and aiding refugees fleeing violence around the world – about two-in-ten Americans describe these as top concerns. These assessments come amid a recent global surge in asylum claims . Still, in Center surveys, democracy promotion has typically been at the bottom of Americans’ list of foreign policy priorities, even dating back to George W. Bush’s and Barack Obama’s administrations .

Overall, a majority of Americans say that all 22 long-range foreign policy goals we asked about should be given at least some priority. Still, about three-in-ten Americans say supporting Israel (31%), promoting democracy (28%) and supporting Ukraine (27%) should be given no priority.

The long-range foreign policy priority questions were also asked in 2018 and 2021, and since then there have been some significant shifts in responses:

• Since 2018, the public has become significantly more likely to say limiting the power and influence of China (+17 percentage points) and finding a solution to the Israeli-Palestinian conflict (+11) are top foreign policy priorities.
• Americans have also increased the emphasis they place on limiting the power and influence of Russia, particularly in the wake of the Russian invasion of Ukraine (+8 points since 2021).
• On the decline since 2018 are strengthening the UN and aiding refugees (-8 points each), reducing foreign military commitments (-6), and promoting and defending human rights in other countries (-5).
• Preventing the spread of infectious diseases is down 19 percentage points since 2021 – during the height of the COVID-19 pandemic – and about back to where it was in 2018.

These are among the findings from a Pew Research Center survey conducted April 1-7, 2024.

The survey of 3,600 U.S. adults shows that foreign policy remains a partisan issue. Republicans prioritize the prevention of terrorism, reducing the flow of illegal drugs into the country, and maintaining a military advantage over other nations. Meanwhile, Democrats prioritize dealing with climate change and preventing the spread of weapons of mass destruction (WMDs), but also preventing terrorist attacks.

There are also stark age differences on many of the policy goals mentioned, but for the most part, young adults are less likely than older Americans to say the issues we asked about are top priorities. The exceptions are dealing with climate change, reducing military commitments overseas, and promoting and defending human rights abroad – on these issues, 18- to 29-year-olds are significantly more likely than older Americans to assign top priority.

Even with these priorities, foreign policy generally takes the backset to domestic policy for most Americans: 83% say it is more important for President Joe Biden to focus on domestic policy, compared with 14% who say he should focus on foreign policy.

Americans are even less likely to prioritize international affairs than they were in 2019, when 74% wanted then-President Donald Trump to focus on domestic policy and 23% said he should focus on foreign policy.

Americans’ foreign policy priorities differ greatly by party. The largest divide, by a significant margin, is the 55 percentage point gap between Democrats and Republicans on dealing with global climate change (70% vs. 15%, respectively, see it as a top priority).

Supporting Ukraine, aiding refugees, reducing the spread of diseases, protecting human rights, and strengthening the UN are also issues on which Democrats are at least 20 points more likely than Republicans to prioritize. For example, 63% of Democrats say reducing the spread of infectious diseases is a top priority, compared with 41% of Republicans.

Republicans prioritize supporting Israel, reducing the flow of illegal drugs and maintaining a military advantage over other countries – among other security and hard power issues – significantly more than Democrats do. For example, more than half of Republicans (54%) say getting other countries to assume more of the costs of maintaining world order should be a top focus in foreign policy. Only a third of Democrats say the same.

The priority assigned to several issues is divided even further by ideology within parties. Take support for Israel and Ukraine as examples. Supporting Israel is generally a higher priority for Republicans than Democrats, but within the Republican Party, 48% of conservatives say it’s a top concern, while 18% of moderates and liberals agree. Previous Center research shows that conservative Republicans are especially likely to favor military aid to Israel .

Supporting Ukraine, something Democrats emphasize more than Republicans, is a top priority particularly for liberal Democrats (47%), while about three-in-ten moderate and conservative Democrats agree (29%). Democrats have also shown more willingness than Republicans to provide aid to Ukraine in its conflict with Russia.

Generally, the partisan differences on the importance of several foreign policy issues have gotten smaller since 2021 , when most of these questions were last fielded. This is especially true for items related to the relative power of major countries, like the U.S. maintaining a military advantage and limiting the power and influence of both Russia and China.

However, finding a solution to the conflict between Israelis and Palestinians – a priority that saw no partisan difference at all when it was last asked about in 2018 – has an emerging partisan gap today. The share of Democrats who call this a top priority has more than doubled, while the share of Republicans has changed little.

Age differences persist on foreign policy issues. Older Americans prioritize most of the issues we asked about at higher rates than those ages 18 t0 29.

On four issues, there is at least a 40 percentage point gap between Americans ages 65 and older and young adults ages 18 to 29. The oldest Americans are more likely to prioritize reducing the flow of illegal drugs, limiting the power and influence of China and Iran, and maintaining a U.S. military advantage.

Those in the oldest age group are also more concerned than their younger counterparts on an additional 11 issues, ranging from support for Israel to U.S. leadership in space exploration.

For their part, young adults are more likely to say dealing with global climate change, reducing U.S. military commitments overseas, and promoting and defending human rights in other countries should be top foreign policy priorities.

Even starker patterns appear when looking at partisanship within two age groups – adults ages 18 to 49 and those 50 and older.

Among Democrats, older adults place particularly high priority on supporting Ukraine, strengthening NATO, and limiting the power and influence of Russia amid its war with Ukraine. Older Democrats are also more likely than younger ones to prioritize preventing the development of WMDs, curbing the spread of diseases, strengthening the UN and promoting democracy around the world, among other issues.

Among Republicans, those ages 50 and older are more likely than those ages 18 to 49 to prioritize supporting Israel, limiting the power and influence of Iran and China, getting other countries to assume more foreign policy costs, reducing the amount of illegal drugs entering the U.S., preventing terrorism, and maintaining a military advantage.

Sign up for our weekly newsletter

Fresh data delivery Saturday mornings

Sign up for The Briefing

Weekly updates on the world of news & information

• Environment & Climate
• Global Health
• Human Rights
• International Affairs
• United Nations
• War & International Conflict

A growing share of Americans have little or no confidence in Netanyahu

Fewer americans view the united nations favorably than in 2023, rising numbers of americans say jews and muslims face a lot of discrimination, younger americans stand out in their views of the israel-hamas war, how u.s. muslims are experiencing the israel-hamas war, most popular, report materials.

1615 L St. NW, Suite 800 Washington, DC 20036 USA (+1) 202-419-4300 | Main (+1) 202-857-8562 | Fax (+1) 202-419-4372 |  Media Inquiries

Research Topics

• Age & Generations
• Coronavirus (COVID-19)
• Economy & Work
• Family & Relationships
• Gender & LGBTQ
• Immigration & Migration
• Internet & Technology
• Methodological Research
• News Habits & Media
• Non-U.S. Governments
• Other Topics
• Politics & Policy
• Race & Ethnicity
• Email Newsletters

ABOUT PEW RESEARCH CENTER  Pew Research Center is a nonpartisan fact tank that informs the public about the issues, attitudes and trends shaping the world. It conducts public opinion polling, demographic research, media content analysis and other empirical social science research. Pew Research Center does not take policy positions. It is a subsidiary of  The Pew Charitable Trusts .

Copyright 2024 Pew Research Center

Terms & Conditions

Privacy Policy

Cookie Settings

Reprints, Permissions & Use Policy