research paper chapter 2 synthesis sample

• 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: Aug 12, 2024 11:48 AM
• 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

How to Synthesize Written Information from Multiple Sources

Shona McCombes

Content Manager

B.A., English Literature, University of Glasgow

Shona McCombes is the content manager at Scribbr, Netherlands.

Learn about our Editorial Process

Saul McLeod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul McLeod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

On This Page:

When you write a literature review or essay, you have to go beyond just summarizing the articles you’ve read – you need to synthesize the literature to show how it all fits together (and how your own research fits in).

Synthesizing simply means combining. Instead of summarizing the main points of each source in turn, you put together the ideas and findings of multiple sources in order to make an overall point.

At the most basic level, this involves looking for similarities and differences between your sources. Your synthesis should show the reader where the sources overlap and where they diverge.

Unsynthesized Example

Franz (2008) studied undergraduate online students. He looked at 17 females and 18 males and found that none of them liked APA. According to Franz, the evidence suggested that all students are reluctant to learn citations style. Perez (2010) also studies undergraduate students. She looked at 42 females and 50 males and found that males were significantly more inclined to use citation software ( p < .05). Findings suggest that females might graduate sooner. Goldstein (2012) looked at British undergraduates. Among a sample of 50, all females, all confident in their abilities to cite and were eager to write their dissertations.

Synthesized Example

Studies of undergraduate students reveal conflicting conclusions regarding relationships between advanced scholarly study and citation efficacy. Although Franz (2008) found that no participants enjoyed learning citation style, Goldstein (2012) determined in a larger study that all participants watched felt comfortable citing sources, suggesting that variables among participant and control group populations must be examined more closely. Although Perez (2010) expanded on Franz’s original study with a larger, more diverse sample…

Step 1: Organize your sources

After collecting the relevant literature, you’ve got a lot of information to work through, and no clear idea of how it all fits together.

Before you can start writing, you need to organize your notes in a way that allows you to see the relationships between sources.

One way to begin synthesizing the literature is to put your notes into a table. Depending on your topic and the type of literature you’re dealing with, there are a couple of different ways you can organize this.

Summary table

A summary table collates the key points of each source under consistent headings. This is a good approach if your sources tend to have a similar structure – for instance, if they’re all empirical papers.

Each row in the table lists one source, and each column identifies a specific part of the source. You can decide which headings to include based on what’s most relevant to the literature you’re dealing with.

For example, you might include columns for things like aims, methods, variables, population, sample size, and conclusion.

For each study, you briefly summarize each of these aspects. You can also include columns for your own evaluation and analysis.

The summary table gives you a quick overview of the key points of each source. This allows you to group sources by relevant similarities, as well as noticing important differences or contradictions in their findings.

Synthesis matrix

A synthesis matrix is useful when your sources are more varied in their purpose and structure – for example, when you’re dealing with books and essays making various different arguments about a topic.

Each column in the table lists one source. Each row is labeled with a specific concept, topic or theme that recurs across all or most of the sources.

Then, for each source, you summarize the main points or arguments related to the theme.

The purposes of the table is to identify the common points that connect the sources, as well as identifying points where they diverge or disagree.

Step 2: Outline your structure

Now you should have a clear overview of the main connections and differences between the sources you’ve read. Next, you need to decide how you’ll group them together and the order in which you’ll discuss them.

For shorter papers, your outline can just identify the focus of each paragraph; for longer papers, you might want to divide it into sections with headings.

There are a few different approaches you can take to help you structure your synthesis.

If your sources cover a broad time period, and you found patterns in how researchers approached the topic over time, you can organize your discussion chronologically .

That doesn’t mean you just summarize each paper in chronological order; instead, you should group articles into time periods and identify what they have in common, as well as signalling important turning points or developments in the literature.

If the literature covers various different topics, you can organize it thematically .

That means that each paragraph or section focuses on a specific theme and explains how that theme is approached in the literature.

Source Used with Permission: The Chicago School

If you’re drawing on literature from various different fields or they use a wide variety of research methods, you can organize your sources methodologically .

That means grouping together studies based on the type of research they did and discussing the findings that emerged from each method.

If your topic involves a debate between different schools of thought, you can organize it theoretically .

That means comparing the different theories that have been developed and grouping together papers based on the position or perspective they take on the topic, as well as evaluating which arguments are most convincing.

Step 3: Write paragraphs with topic sentences

What sets a synthesis apart from a summary is that it combines various sources. The easiest way to think about this is that each paragraph should discuss a few different sources, and you should be able to condense the overall point of the paragraph into one sentence.

This is called a topic sentence , and it usually appears at the start of the paragraph. The topic sentence signals what the whole paragraph is about; every sentence in the paragraph should be clearly related to it.

A topic sentence can be a simple summary of the paragraph’s content:

“Early research on [x] focused heavily on [y].”

For an effective synthesis, you can use topic sentences to link back to the previous paragraph, highlighting a point of debate or critique:

“Several scholars have pointed out the flaws in this approach.” “While recent research has attempted to address the problem, many of these studies have methodological flaws that limit their validity.”

By using topic sentences, you can ensure that your paragraphs are coherent and clearly show the connections between the articles you are discussing.

As you write your paragraphs, avoid quoting directly from sources: use your own words to explain the commonalities and differences that you found in the literature.

Don’t try to cover every single point from every single source – the key to synthesizing is to extract the most important and relevant information and combine it to give your reader an overall picture of the state of knowledge on your topic.

Step 4: Revise, edit and proofread

Like any other piece of academic writing, synthesizing literature doesn’t happen all in one go – it involves redrafting, revising, editing and proofreading your work.

Checklist for Synthesis

•   Do I introduce the paragraph with a clear, focused topic sentence?
•   Do I discuss more than one source in the paragraph?
•   Do I mention only the most relevant findings, rather than describing every part of the studies?
•   Do I discuss the similarities or differences between the sources, rather than summarizing each source in turn?
•   Do I put the findings or arguments of the sources in my own words?
•   Is the paragraph organized around a single idea?
•   Is the paragraph directly relevant to my research question or topic?
•   Is there a logical transition from this paragraph to the next one?

Further Information

How to Synthesise: a Step-by-Step Approach

Help…I”ve Been Asked to Synthesize!

Learn how to Synthesise (combine information from sources)

How to write a Psychology Essay

Academia.edu no longer supports Internet Explorer.

To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to  upgrade your browser .

Enter the email address you signed up with and we'll email you a reset link.

• We're Hiring!
• Help Center

CHAPTER 2 REVIEW OF RELATED LITERATURE AND STUDIES

Related Papers

Ana Liza Sigue

Motoky Hayakawa

Rene E Ofreneo

... Rene E. Ofreneo University of the Philippines School of Labor and Industrial Relations ... Erickson, Christopher L.; Kuruvilla, Sarosh ; Ofreneo, Rene E.; and Ortiz, Maria Asuncion , &amp;quot;Recent Developments in Employment Relations in the Philippines&amp;quot; (2001). ...

Lucita Lazo

This book begins by looking at the status of women in Filipino society and their place in the general socio-economic situation. It continues with sections on education and training in the Philippines and work and training. The next section reviews the constraints to women’s participation in training. In the summary the author gives a general overview of the situation of women and opportunities for work and training in the Philippines and offers some practical suggestions for the enhancement of women’s training and development.

EducationInvestor Global

Tony Mitchener

Rosalyn Eder

In this article, I examine the role of CHED and the Technical Panels (TPs) in the “production” of the globally competitive Filipina/o worker. For this paper, I draw on relevant literature on the topic and take nurse education, which is rooted in the colonial system established during the US-American occupation, as an example of how CHED and the TPs could be more linked to labor migration. I use the colonial difference - a space that offers critical insights and interpretation - to illustrate how coloniality remains hidden under the cloak of modernity. Link to the article: http://dx.doi.org/10.1080/00131946.2016.1214913

Asia Pacific Journal of Management and Sustainable Development ISSN 2782-8557(Print)

Ryan O Tayco , Pio Supat

This study aims to determine the employability of the Negros Oriental State University graduates from 2016 to 2020. Employability is measured using different dimensions-from the graduates' side including the perspectives of the employers. A total of 1, 056 NORSU graduates and 68 employers locally and abroad answered the questionnaire through online and offline survey methods. Basic statistics were used and simple linear regression was also used to estimate the relationship between manifestations of respondents in NORSU VMGOs and the job performance as perceived by the employers. Most of the respondents in the study are presently employed and work locally. Many of them stay and accept the job because of the salaries and benefits they received, a career challenge, and related to the course they have taken in college. The study shows that the curriculum used and competencies learned by the NORSU graduates are relevant to their job. Competencies such as communication skills, human relations skills, critical thinking skills, and problem-solving skills are found to be useful by the respondents. It is found that the manifestation of the respondents is very high and homogenous. The same can be said with job performance as perceived by employers in terms of attitudes and values, skills and competencies, and knowledge. Furthermore, job performance and the manifestation of NORSU VMGOs have a significant relationship. That is, those respondents who have higher job performance in terms of attitude and values, skills and competencies, and knowledge have higher manifestations of NORSU VMGOs.

Annals of Tropical Research

Pedro Armenia

Ezekiel Succor

Loading Preview

Sorry, preview is currently unavailable. You can download the paper by clicking the button above.

RELATED PAPERS

The Miseducation of the Filipino

Micabalo, Sheila Marie G.

Evan carlo deblois

Jesse Orlina

Bradernantz Geronag

Junie Leonard Herrera

Asian and Pacific Migration Journal

boscovolunteeraction.co.uk

James Trewby

Asia Proceedings of Social Sciences

Marlon Raquel

Kiran Budhrani , Lloyd Espiritu

Leonardo Lanzona

MaryNathanael Flores OSB

Philippine Journal of …

Nandy Aldaba

South African Journal of Higher Education

Kolawole Samuel Adeyemo

International Journal of Intelligent Computing and Technology

Glenn Velmonte

Rosini Grageda

Randel D Estacio

Reydenn Taccad

International Research in Education

Diane Mae Ulanday

Miseducation of Filipino

John Victor H . Dajac

Douglas Meade

Rebecca Gaddi

Jayvann Carlo Olaguer

Lorena Club

Trisha Bernadette Ecleo

Sara Villorente

•   We're Hiring!
•   Help Center
• Find new research papers in:
• Health Sciences
• Earth Sciences
• Cognitive Science
• Mathematics
• Computer Science
• Academia ©2024

Library Guides

Literature reviews: synthesis.

• Criticality

Synthesise Information

So, how can you create paragraphs within your literature review that demonstrates your knowledge of the scholarship that has been done in your field of study?  

You will need to present a synthesis of the texts you read.  

Doug Specht, Senior Lecturer at the Westminster School of Media and Communication, explains synthesis for us in the following video:  

Synthesising Texts  

What is synthesis? 

Synthesis is an important element of academic writing, demonstrating comprehension, analysis, evaluation and original creation.  

With synthesis you extract content from different sources to create an original text. While paraphrase and summary maintain the structure of the given source(s), with synthesis you create a new structure.  

The sources will provide different perspectives and evidence on a topic. They will be put together when agreeing, contrasted when disagreeing. The sources must be referenced.  

Perfect your synthesis by showing the flow of your reasoning, expressing critical evaluation of the sources and drawing conclusions.  

When you synthesise think of "using strategic thinking to resolve a problem requiring the integration of diverse pieces of information around a structuring theme" (Mateos and Sole 2009, p448). 

Synthesis is a complex activity, which requires a high degree of comprehension and active engagement with the subject. As you progress in higher education, so increase the expectations on your abilities to synthesise. 

How to synthesise in a literature review: 

Identify themes/issues you'd like to discuss in the literature review. Think of an outline.  

Read the literature and identify these themes/issues.  

Critically analyse the texts asking: how does the text I'm reading relate to the other texts I've read on the same topic? Is it in agreement? Does it differ in its perspective? Is it stronger or weaker? How does it differ (could be scope, methods, year of publication etc.). Draw your conclusions on the state of the literature on the topic.  

Start writing your literature review, structuring it according to the outline you planned.  

Put together sources stating the same point; contrast sources presenting counter-arguments or different points.  

Present your critical analysis.  

Always provide the references. 

The best synthesis requires a "recursive process" whereby you read the source texts, identify relevant parts, take notes, produce drafts, re-read the source texts, revise your text, re-write... (Mateos and Sole, 2009). 

What is good synthesis?  

The quality of your synthesis can be assessed considering the following (Mateos and Sole, 2009, p439):  

Integration and connection of the information from the source texts around a structuring theme. 

Selection of ideas necessary for producing the synthesis. 

Appropriateness of the interpretation.  

Elaboration of the content.  

Example of Synthesis

Original texts (fictitious): 

Synthesis: 

Animal experimentation is a subject of heated debate. Some argue that painful experiments should be banned. Indeed it has been demonstrated that such experiments make animals suffer physically and psychologically (Chowdhury 2012; Panatta and Hudson 2016). On the other hand, it has been argued that animal experimentation can save human lives and reduce harm on humans (Smith 2008). This argument is only valid for toxicological testing, not for tests that, for example, merely improve the efficacy of a cosmetic (Turner 2015). It can be suggested that animal experimentation should be regulated to only allow toxicological risk assessment, and the suffering to the animals should be minimised.   

Bibliography

Mateos, M. and Sole, I. (2009). Synthesising Information from various texts: A Study of Procedures and Products at Different Educational Levels. European Journal of Psychology of Education,  24 (4), 435-451. Available from https://doi.org/10.1007/BF03178760 [Accessed 29 June 2021].

• << Previous: Structure
• Next: Criticality >>
• Last Updated: Nov 18, 2023 10:56 PM
• URL: https://libguides.westminster.ac.uk/literature-reviews

CONNECT WITH US

• Welcome to Chapter 2

How to Critically Analyze Sources

Learning about synthesis analysis, chapter 2 webinars.

• Student Experience Feedback Buttons
• Library Guide: Research Process This link opens in a new window
• ASC Guide: Outlining and Annotating This link opens in a new window
• Library Guide: Organizing Research & Citations This link opens in a new window
• Library Guide: RefWorks This link opens in a new window
• Library Guide: Copyright Information This link opens in a new window
• Library Research Consultations This link opens in a new window

Jump to DSE Guide

Need help ask us.

• Research Process An introduction to the research process.
• Determining Information Needs A Review Scholarly Journals and Other Information Sources.
• Evaluating Information Sources This page explains how to evaluate the sources of information you locate in your searches.
• Video: Doctoral Level Critique in the Literature Review This video provides doctoral candidates an overview of the importance of doctoral-level critique in the Literature Review in Chapter 2 of their dissertation.

What D oes Synthesis and Analysis Mean?

Synthesis: the combination of ideas to

• show commonalities or patterns

Analysis: a detailed examination

• of elements, ideas, or the structure of something
• can be a basis for discussion or interpretation

Synthesis and Analysis: combine and examine ideas to

• show how commonalities, patterns, and elements fit together
• form a unified point for a theory, discussion, or interpretation
• develop an informed evaluation of the idea by presenting several different viewpoints and/or ideas
• Article Spreadsheet Example (Article Organization Matrix) Use this spreadsheet to help you organize your articles as you research your topic.

Was this resource helpful?

• Next: Library Guide: Research Process >>
• Last Updated: Apr 19, 2023 11:59 AM
• URL: https://resources.nu.edu/c.php?g=1007176

© Copyright 2024 National University. All Rights Reserved.

Privacy Policy | Consumer Information

Have a language expert improve your writing

Run a free plagiarism check in 10 minutes, generate accurate citations for free.

• Knowledge Base

Methodology

• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

Instantly correct all language mistakes in your text

Upload your document to correct all your mistakes in minutes

Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

Receive feedback on language, structure, and formatting

Professional editors proofread and edit your paper by focusing on:

• Academic style
• Vague sentences
• Style consistency

See an example

Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

Don't submit your assignments before you do this

The academic proofreading tool has been trained on 1000s of academic texts. Making it the most accurate and reliable proofreading tool for students. Free citation check included.

Try for free

To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• 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 sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

Open Google Slides Download PowerPoint

If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

• Sampling methods
• Simple random sampling
• Stratified sampling
• Cluster sampling
• Likert scales
• Reproducibility

 Statistics

• Null hypothesis
• Statistical power
• Probability distribution
• Effect size
• Poisson distribution

Research bias

• Optimism bias
• Cognitive bias
• Implicit bias
• Hawthorne effect
• Anchoring bias
• Explicit bias

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

Cite this Scribbr article

If you want to cite this source, you can copy and paste the citation or click the “Cite this Scribbr article” button to automatically add the citation to our free Citation Generator.

McCombes, S. (2023, September 11). How to Write a Literature Review | Guide, Examples, & Templates. Scribbr. Retrieved August 12, 2024, from https://www.scribbr.com/dissertation/literature-review/

Is this article helpful?

Shona McCombes

Other students also liked, what is a theoretical framework | guide to organizing, what is a research methodology | steps & tips, how to write a research proposal | examples & templates, get unlimited documents corrected.

✔ Free APA citation check included ✔ Unlimited document corrections ✔ Specialized in correcting academic texts

Risk-Based Inspection and Strength Evaluation of Suspension Bridge Main Cable Systems (2023)

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.

5 C H A P T E R 2 Literature Review and Synthesis Literature Review Purpose of Literature Review NCHRP 534 represents the current guidelines followed by bridge owners for planning and conducting inspections of main cables of suspension bridges and for estimating their remaining strength. The literature review for the present project used this previous NCHRP effort as a starting point. Rather than repeating all the information gathered during the development of NCHRP 534, attention was focused on the developments that have occurred on inspection methods and assessment of the remaining cable strength of main cables of suspension bridges from the publication of the NCHRP 534 report to the present. An effort was made to highlight the knowledge gaps between state of the-art and current guidelines. Literature Review Process The literature review effort started from the body of work contained in the NCHRP 534 Guidelines and built on it, looking at the published work produced from 2004 until the present. The review was conducted using the library search engines of Columbia University together with inspection reports and studies available to the members of the research team. The search focused on international peer- reviewed journals like the American Society of Civil Engineers (ASCE) Journal of Bridge Engineering and the ASCE Journal of Structural Engineering, as well as bridge-specific conference proceedings. Rather than including it here, an annotated bibliography, e.g. the full list of literature reviewed, along with a summary of each document, is provided in Appendix A. With regard to the assessment of the main cable's strength, it appears that, from the results of the literature review, the vast majority of the published work has been done by members of this research team. The focal point appears to be the 2007 paper by Shi, Deodatis and Betti where a random field methodology was introduced as a more rigorous and accurate alternative to the one presented in the NCHRP 534 Guidelines. Although not officially applied in the field, this methodology has been published in peer-reviewed journals and validated by comparison to currently used methods. It has been used in various publications to study a variety of related problems (e.g. inter-wire friction, time- dependent corrosion rate, thermal effects, etc.). It represents the springboard for the development of the new methodology proposed in this study. The literature search revealed the existence of an additional method for computing the remaining strength of a cable: it is the BTC method, a proprietary method proposed by Bridge Technology Consulting. With regard to cable inspections, few studies were found where Nondestructive Techniques (NDT) were used in the inspection of main cables. The FHWA Report (FHWA-HRT-14-023), produced by

6 members of this research team, contains an up-to-date review of NDT technologies, e.g. Acoustic Emission, Magnetostrictive, Flux Leakage, used in practice and research and was used as the starting point for the work done in this study. Identification of Knowledge Gaps Following the general approach presented in NCHRP NCHRP Report 534, the tasks required for a proper assessment of the remaining strength of a parallel wire cable involve the following steps: 1) Inspecting and mapping the corrosion grades across the cross-section of the cable, 2) Extracting wire samples from the various corrosion grades, 3) Developing wire stress-strain diagrams using tests of extracted wires, 4) Finding the minimum strength of a given length of wire, 5) Calculating probabilistic characteristics describing how the strength of wires vary within the cross-section and along the length of the cable, 6) Estimating the number of cracked and broken wires within a panel, 7) Determining the effectiveness of the cable bands in redeveloping the strength of a wire broken at some distance from the point at which the strength is being determined, 8) Estimating the effect on the cable strength of a given panel of the deterioration in panels near the one being evaluated, 9) Estimating the strength of the cable in a given panel based on this data. While Steps 1 through 3 are well defined and regulated by precise procedural standards, Steps 4) and 5) require some clarifications. Steps 4) and 5) involve the description of a wire "of a given length". If this "given length of the wire" is made of n unit segments (specimens), the strength of such a length of wire can be calculated to be the minimum of the n strengths of the n unit segments (weakest link model). This computation can be done either by using some extreme value distribution (exact or asymptotic), or through equivalent Monte Carlo simulations. In most of the publications on this topic, we found that there is an inherent assumption made in this standard procedure: the n random variables that model the strength of the n successive unit length segments along the wire "of a given length" are independent (e.g. the corresponding n strengths are uncorrelated). This is an assumption that it is acceptable when dealing with brittle and quasi-brittle materials but it is highly questionable and potentially wrong for a ductile material like steel. It is with the pivotal paper by Shi et al. (2007) that the spatial correlation of the wire strength along its length was introduced in the estimation of the strength of suspension bridge cables. In the approach proposed by Shi et al. (2007), the strength of a wire of length equal to n unit length segments is modeled as a Random Field (e.g. as n correlated random variables). This approach was successfully applied to the estimation of the remaining cable strength of the Williamsburg Bridge (New York City, NY). From the literature review, we found that there are four basic variations of the standard approach, based on four different ways to estimate the strength of a wire consisting of n unit length segments: 1) using the exact extreme value distribution (EVD) of the smallest value of the strength (Exact EVD), 2) using Type I asymptotic distribution of the smallest value (Type I EVD), 3) using a Type Ill asymptotic distribution of the smallest value (Type Ill EVD, also known as the Weibull distribution), and

7 4) using Monte Carlo simulations reflecting the EVD (simulating independent and identically distributed random variables). This last approach is basically equivalent to numerically computing the results of the Exact EVD approach: it requires that: 1) the wire "of a given length" be modeled as n uncorrelated random variables, each describing the strength of a unit length wire segment, 2) select an initial distribution (e.g. lognormal, beta) of the strength of a unit length segment, 3) generate n unit length segment strengths from the selected initial distribution, 4) determine the smallest strength among the n generated strengths and this will be the strength of the wire "of a given length", and 5) repeat this procedure a large number of times to generate the statistics of the strength of a wire "of a given length". All the previous studies and guidelines for assessing the remaining strengths of suspension bridge cables have been based on such methodologies. In 1988, Steinman et al. attempted to estimate the strength of the Williamsburg Bridge main cable by assuming, as the initial distribution for the strength of 1-ft-long wire segment, a Gaussian distribution and then used the assumption of n independent and identically distributed random variables to estimate the strength of a wire of length equal to n units. The shortcoming of this approach was the use of a Gaussian distribution, since it allows the strength of a unit length segment to assume negative values, something that is physically impossible. However, while from a purely theoretical point of view, only distributions that assume nonnegative values should be considered, the Gaussian distribution provides reasonably good estimates (the left tail of the Gaussian distribution becomes negligibly thin for negative values of the strength). Following the same approach, Matteo et al. (1994) used the Gaussian distribution as the initial distribution and then used a Type I EVD approach to find the strength of a wire of a given length. A similar approach based on Type I EVD was used by Haight et al. (1997) to assess the remaining strength of main cables for four suspension bridges. It was in 1998 that Perry introduced the Type Ill EVD model for the reliability analysis of the Williamsburg Bridge cables and this type model, together with the Type I EVD, was set into standard in the NCHRP NCHRP Report 534 (2004). It should be mentioned that from a practical point of view, the aforementioned two distributions (Type I and Type Ill) yield almost identical results. It was Shi et al. (2007) that established a new approach in the way cable strength should be calculated. Looking at the laboratory results from the testing of 330 wire segments, they found that the probability distribution function that best fits the data is a beta probability distribution function (limited to positive values only). In addition, having the sequential order of the segments along the long samples removed from the bridge cable, they were able to estimate an autocorrelation function for the wire strength as a function of the separation distance along the length of the wire. A Monte Carlo approach was then used to generate a large number of realizations from which it was possible to obtain the mean and the standard deviation of the cable's strength. This approach, by accounting for the correlation of the wire strength along the length of the cable and its inherent non-Gaussianity, provided estimations of the mean strength of the cable that were about 10%-12% higher than those obtained from the previous methods. Estimating the number of cracked and broken wires in a cable has a pronounced impact on the estimation of cable strength. Very little information is contained in the current literature about how to

8 establish the percentage of cracked and broken wires. The methodology contained in NCHRP 534 is, at present, the only approach that is being used. A review of inspection reports indicates that little data has been collected as to the observed distribution of cracked and broken wires. Developing an inspection procedure and statistical methodology for a more reliable method of establishing these parameters and how they impact cable strength was a goal of this project. In computing the remaining strength of a parallel wire cable, an important parameter is represented by the redevelopment length of a broken wire. This is the length that it takes for a broken wire to regain its full strength through friction with the surrounding wires. Hence, it is strongly dependent on the level of compaction of the cable, as induced by the cable bands. Until recently, the redevelopment length was estimated by the retraction distances when samples were cut and was usually considered equal to two panel lengths on each side of fracture surface (NCHRP NCHRP Report 534, 2004). In the past few years, work done at Columbia University (Noyan et al., 2010, Betti et al., 2011) has focused on the friction among wires and on how it affects the strain (stress) transfer from a broken wire to the surrounding wires. Using neutron diffraction technology on small strands of parallel (steel and aluminum) wires, Noyan et al. (2010) have shown that the length from the fracture surface to the point where the wire has regained its full strength is much shorter than the one previously estimated. These results have been incorporated in various finite element analyses to assess the friction effect on the estimation of the cable strength (Betti et al., 2011). The effects of this conclusion are further investigated for potential changes in the guidelines. With respect to the inspection of a parallel wire main cable of a suspension bridge, very little information is available in the current literature. The current practice of visual inspection, consisting in unwrapping, wedging and visually classifying the exposed wire into 4-5 categories, is still the only one that is used in field investigations for assessing the cable strength. However, even in the case of unwrapping the entire length of a cable, this practice provides only a limited amount of information because the amount of wires exposed (and consequently inspected) is still a quite small percentage of the entirety of wires. Consequently, the effectiveness of the various methodologies for estimating the remaining cable strength is affected by the reliability and completeness of such a limited information. In recent years, thanks to the advances in sensor technologies, a variety of nondestructive evaluation technologies (e.g. acoustic emission, magneto-strictive, fiber optic gauges, etc.) has appeared on the stage of cable inspection but the results, so far, have been inconclusive. The major stumbling problem for their success is represented by the size of a main cable of a suspension bridge. While all of these technologies are valid and cost-effective for small bundles of wires, like a strand at the anchorage point, they have difficulties when presented with an enormous bundle of wires such as a main cable. A recent report from FHWA (FHWA-HRT-14-023), released in May 2014 and prepared by members of this research team, provides a comprehensive assessment of the state of the-art in main cable inspection technologies, highlighting the strengths as well as limitations of each method. The following NDE technologies were evaluated: • Acoustic Emission (AE) • Magnetostrictive (MS) • Fiber optics (pH, humidity, chloride content, strain, etc.) • Electromagnetic (magnetic flux leakage) • Linear Polarization Resistance (LPR) • Electrochemical impedence spectroscopy The results of this research were promising. They showed that commercially available sensors are capable of providing useful information about the environmental conditions within the interior of a

9 main cable, and that they are sufficiently durable to survive the rigors of field installation. The ability to monitor variables such as temperature and humidity can be used as indirect indicators of the potential for corrosion activity. Several direct sensing systems were also identified as having a strong potential for future applications, these included the main flux method and a system based on a combination of AE and MS technologies (the latter being applicable to smaller strands, such as those found in anchorages). Based on the literature review performed by the research team, there have not been any noteworthy advances in the NDE/SHM technology from the results published in 2014. It should be noted that the scope of the literature review was to identify information on commercially available NDE technologies, as well as SHM and other bridge preservation technologies such as dehumidification, that are relevant to suspension bridges in general and main cables in particular. It should be further noted that the development of new NDE methods for cable inspection and/or evaluation is outside the scope of this project. Synthesis of Survey Purpose of Survey The previous NCHRP effort, which led to the development of NCHRP 534, that represents the current guidelines followed by bridge owners for planning and conducting inspections of main cables of suspension bridges and for estimating their remaining strength, was based upon data from primarily two bridges with partial information from one other. Now that the methodology developed under NCHRP 534 has been in use since 2004, and numerous bridges have been inspected and evaluated using NCHRP 534, it was felt that most data was available than was the case in 2004. In addition, the use of NCHRP 534 for many more bridge inspections could reveal any shortcomings in the present methodology as well as establish areas that the present approach could be improved. An effort was made to highlight the knowledge gaps between state of the-art and current guidelines. Survey Process and Summary of Results A survey was developed by the research team and was sent by e-mail to the owners of approximately 70 suspension bridges located in North America, Europe and Asia. Responses were received addressing 21 bridges located in North America and Europe. Sixteen bridges were in North America and five were in Europe. No responses were received from Asian bridge owners. Of the 21 bridges, 17 utilized parallel wire cables and four had helical strand cables. A copy of the questionnaire is included in Appendix A. Due to security concerns, many of the bridge owners requested that the data received be “masked” in such a way that the data could not be associated with any specific bridge. For this reason, the RT made the decision to summarize the data in ranges and charts in such a way that no direct association can be made of the data and a specific bridge. A summary of the results are as follows and is presented in the same order and question numbers used in the questionnaire. Q1.0 Organization. (21 Responses) Of the 21 bridges for which data was received, 15 of the bridges were owned by Authorities, five were owned by departments of transportation and one was from a private owner. Q2.0 Keep Information out of the Public Domain?

10 As stated above, for reasons of security, most of the bridge owners requested that the data provided not be specifically associated with their bridge. Q3.0 Description of Suspension Bridge. (21 Responses) Q3.1 Name of the Bridge. (21 Responses) For reasons of security, most of the bridge owners requested that the bridge name not be used due to concern that the data provided might be specifically associated with their bridge. For this reason, no bridge names are presented in the data summaries. Q3.2 Date Opened to Traffic. (21 Responses) Date Opened to traffic. Of the responses received, the oldest bridge opened to traffic in 1921 and the newest opened to traffic in 1997. Figure 1. Period Bridges Opened to Traffic Q3.3 Roadway Carried. (21 Responses) Roadways carried included interstate highways, state highways, local streets and privately-owned roadways. Q3.4 Length – Anchorage to Anchorage. (19 Responses) Of the responses received, the total bridge length (Anchorage to Anchorage ranged from just under 2,000 feet to 9,570 feet).

11 Figure 2. Total Length of Bridge (in feet) Q3.5 Span Arrangement. (20 Responses) Q3.5.1 Number of Suspended Spans. All but two of the bridges had three suspended spans. Two of the bridges had side spans not supported by the main cables. Q3.5.2 Length of Main Span. The length of main span of the bridges reported ranged from 644 feet to 4,260 feet. The distribution is shown below. Figure 3. Length of Main Span (in feet) Q3.5.3 Length of side spans. As stated above two of the bridges did not have side spans supported by the main cables. The side spans ranged in length from 176 feet to 1800 feet.

12 Figure 4. Length of Side Spans Supported by Main Cables (in feet) Q3.6 Width of Bridge curb to curb. (17 Responses) As illustrated in the graph below, the width of the bridge decks from curb to curb varied from 26 feet to 87 feet with one bridge having two roadways: one with a width of 80 feet and the other a width of 74 feet. Figure 5. Bridge Width (in feet) Q3.6.1 Number of traffic lanes. Four of the bridges carry two lanes of traffic, nine of the bridges carry four lanes of traffic, two carry six lanes of traffic, one carries eight lanes of traffic and one carries 12 lanes of traffic (two levels at six lanes each). Q3.6.2 Width of lanes. Of the bridges for which data was suppled, the lanes widths vary from a minimum of 10 feet to a maximum of 13 feet.

13 Q3.7 Sidewalks. (21 Responses) Fourteen of the bridges reported having sidewalks and seven did not have sidewalks. The widths of the sidewalks ranged in width from 2’-6” to 6 feet. Q4.1 Number of Cables. (21 Responses) Of the 21 bridges for which responses were received, 20 of the bridges had two main suspension cables with one bridge having four cables. Two of the bridges have supplementary cables. Q4.2 Cable Sag. (21 Responses) The cable sag is a measure of the vertical distance from a straight line between the tower saddles to the lowest point on the cable, usually at midspan. The cable sag for the 14 bridges for which the information was provided is shown below. The sag is most often expressed as a sag ratio which is the cable sag divided into the span length. Sixteen respondents reported the sag ratio for their bridge. The sag ratios for the bridges reported as a function of their date of construction are shown in Figure 7. Figure 6. Cable Sag

14 Figure 7. Sag Ratio versus Age Q4.3 Cable Diameters. (21 Responses) Seventeen of the respondents provided the diameter of cables on the bridges. Only the main span diameters are shown below. Two of the bridges have more wires and hence a slightly larger diameter in the side spans due to the span ratio. One of the bridges has four cable all the same diameter. Figure 8. Diameter of Cables (inches) Q4.4 Parallel Wires or Helical Strand? (21 Responses) Of the 21 bridges reported, 17 had parallel wires and four had helical strand comprising the cable. 4.5 Cable Protection System. (21 Responses) 4.5.1 Paste beneath the Wrapping Wire and Paste Material: Of the 21 responses, 19 bridges contained red lead paste with 15 of the bridges reported having had a zinc paste applied in panels that

15 had previously been opened. The remaining two bridges are reported to have a zinc chromate paste. These were both helical strand cables. 4.5.2 Wrapping Wire Used? Characteristics. Of the 21 responses to the questionnaire, 19 bridges have No 9 (0.148” in diameter) wrapping wire. Two of the bridge outside of North America use wrapping wire with diameters of 0.12” and 0.14” in diameter. 4.5.3 Have the cables been oiled? If yes, what material was used? Five bridges were reported to have had their cable oiled, two with raw linseed oil and three using a proprietary Prelube 19 material. Two of the bridges have had both cables oiled for their full length. The remaining bridges have only had the panels that have been opened for inspection oiled. Some of the bridge owners have oiled the strands in the anchorages. 4.5.4 If the cable has been oiled, when was it oiled? Most of the oiling has taken place in concert with cable inspections. The latest oiling of the cables has taken place in 1993, 1994, 1996, 1998, & 2002. 4.5.6 Does the cable have a Flexible Wrapping System? If yes, what material? Six bridges reported have a flexible wrapping material in addition to wrapping wire. One bridge reported use of a “polyethylene” material, three utilized ”Cable Guard” , one has part of its cable wrapped with Cable Guard, and one with a material as being “elastomeric.” 4.5.7 Does the cable have a dehumidification system? If yes, how long has it been in service? Five bridges were reported as having a cable dehumidification system for their main cables. Two bridges had dehumidification systems in service less than 1 year at the time of reporting, one was installed in 2009, one in 2008, and one installed in 2005. Q4.6 For Cables Comprised of Parallel Wires. (17 Responses) Q4.6.1 Diameter of wire used in the main cable: Of the 17 bridges reported to have parallel wire strand, all but one bridge was reported to have galvanized wire that was 0.196”in diameter. The one exception was reported to have a wire diameter of 0.207”. Q4.6.2 Number of Wires in the Main Span Main Cable. The Number of wires reported in the questionnaire ranged from 7,068 wires to 26,108 wires. The distribution is shown in the graph below.

16 Figure 9. Number of Wires in Parallel Wire Cables Q4.6.3 Number of wires in the side Spans. All the bridges containing parallel wires, with the exception of three bridges, were reported to have the same number of wires in the main span and the side spans. Three of the bridges had a small percentage of additional wires in the side spans due to the main span to side span length ratio. Q4.6.4 Mechanical Properties of the Wire? Ten bridge owners provided data regarding the strength of the wires. As can be seen in Figure 10, in most cases the mean tested strength of the various stages of the wire exceeded the original specified strength of the wire. Though not reported in the questionnaire, the standard deviation in the higher stages is typically greater. Figure 10. Mean Wire Strength by Corrosion Stage

17 Q4.6.5 Are the Wires galvanized? Eighteen respondents reported that the wires in their main cables are galvanized. The remaining three did not respond to this question. Q4.7 For Cables Comprised of Helical Strands. (3 Responses) Q4.7.1 For cables comprised of Helical Strands – Type of Strand? On the four bridges reported to have Helical strand two were reported to have Structural Strand – round wire, one was Locked Coil and one did not respond to the question. Q4.7.2 For cables comprised of Helical Strands – Diameter of Helical Strand The strand diameter of one of the three bridges that responded was reported to be 1.47 inches, while the second bridge had a combination of 1.75-inch and 1.25-inch strand. The third bridge had Locked Coil with a diameter of 2.37 inches. Q4.7.3 For cables comprised of Helical Strands – Number of Helical Strands in each Cable? Of the three bridges reported, one bridge was reported to have 61 strands with no diameter reported, while the second was reported to have 31 strands at 1.75 inch and six strands @ 1.25 inch. The bridge with locked coil had a total of 31 strands with no diameter reported. Q4.7.4 For cables comprised of Helical Strands – What Type of Filler Elements were used to make the cable round? One bridge was reported to use Cedar wood fillers; two were reported to have extruded aluminum and one was reported to use a combination of tubular aluminum, solid PVC, and hollow PVC. Q5.0 Main Cable Monitoring System. (21 Responses) Q5.1 Acoustical Monitoring System on the Bridge? Of the 21 responses received, 7 bridges are reported to have an acoustical monitoring system on the main cables. Figure 11. Bridges with Acoustic Monitoring

18 Q5.2 What Acoustical Monitoring System Is Used? Of the seven bridges reported to have an acoustical monitoring system three were installed by Pure and four were installed by MISTRAS. Q5.3 How Long Has the Acoustical System Been in Service? Of the seven bridges reported to have an acoustical monitoring system the oldest was installed in 2001 and the newest installed in 2015 Q5.4 Comments on the Effectiveness of the Acoustical Monitoring System Only one comment was made from one respondent. “Recent upgrades in sensors, cabling, and software have improved the performance of the acoustic monitoring system. Additionally, a wireless network connection over Verizon network has improved communications and reliability.” Q5.5 Health Monitoring System Installed? Of the respondents, none reported the installation of an operating health monitoring system. 5.0.1 Name of health monitoring system used and performance. One bridge had a test installation of various sensors but most of the sensors failed during compaction and rewrapping. No manufacturer was provided in the response. Q6.0 Main Cable Inspection History. Q6.1 Date of Last Cable Inspection. (21 Responses) Of the 21 responses, 19 reported the year of the last inspection, which varied from 1996 to 2018. Two did not respond to the question. See Figure 12 for the distribution of inspection years. Figure 12. Year of Last Inspection Q6.2 How Many Times Has the Cable Been Opened/Inspected? (21 Responses) Only 20 responders provided information on the number of times their cables have been inspected for each bridge ranges from one to nine inspections. One did not respond to the question. See Figure 13 for the response distribution.

19 Figure 13. Number of Times Cables Have Been Inspected Q6.3 Is the Cable Inspected on a Regular Basis? (21 Responses) As shown in Figure 14, of the 21 respondents, only 10 stated that they inspect their bridge cables on a regular basis. Figure 14. Regular Inspections Performed? Q6.3.1 If inspected on a regular basis, on what interval? Of the respondents that stated they performed regular inspections, six stated they inspected the cable every 10 years, three every 5 years and one that stated the next inspection was based on the findings of the previous inspection.

20 Q6.4 Number of Panels Opened During Each Inspection. (20 Responses) Two bridges were reported as having all the panels opened and inspected. In the case of both bridges, this took place prior to the publication of NCHRP 534. Subsequent inspections on one of these two bridges reported opening eight panels for each inspection. Figure 15. Number of Panels Inspected Q6.5 on What Basis Were the Panels Selected for Opening? (20 Responses) As illustrated in Figure 16, location was the primary criteria for selecting panels to open with 13 respondents citing location as at least one reason for selecting a certain panel. The explanation provided in the questionnaire responses stated that understanding of the behavior of a suspension bridge and accessibility were the two main factors that drove the location selected. Results from previous inspections was the primary criteria for four of the bridges while exterior condition of the cable was the primary criteria for four other bridges.

21 Figure 16. Selection Criteria for Opening Panels Q6.6 Were Field Inspection Forms Prepared for Your Bridge? (19 Responses) All 19 respondents stated that inspection forms were prepared for the cable inspection. Those that provided forms closely followed the examples in NCHRP 534. Q6.7 Total Number of Samples Taken for Testing? (17 Responses) Of the 17 parallel wire cables for which responses were received, only 14 reported the number of samples taken with the number ranging from 3 to 122. Q6.8 How Many Specimens Were Tested? (17 Responses) Only 10 of the 17 respondents provided the number of specimens that were taken from the samples. As shown in Figure 17, the number ranged from 11 to 1208. It does not appear that most of the inspections followed the number of samples recommended in NCHRP 534 though it is not possible to emphatically come to that conclusion without knowing if stage 3 and stage 4 wires were present at the time of inspection.

22 Figure 17. Number of Samples and Specimens Q6.9 What Tests Were Conducted on the Specimens? (10 Responses) It appears based on the 10 responses to the questionnaire that the majority of the specimens tested used most, if not all, of the tests recommended in NCHRP 534. Tests reported to have been performed were chemical analysis, tensile tests; coating weight; Preece test; surface chemistry; microscopic examination; fractographic examination; fatigue tests, hydrogen content, analysis of water in the cable, and bacterial testing. It appears that following the initial inspection the testing focus changed to primarily tensile tests, microscopic examinations, and fractographic examination. Q6.10 Please Describe the Sampling Technique Used? (15 Responses) Based on the responses to the questionnaire, most bridges sampled from eight wedge lines located at the 12:00, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00, and 10:30 clock positions. Responders reported samples were typically take from rings no deeper than approximately 2 inches into the cable. Most of the responders reported following NCHRP 534 as far as technique. Only one helical strand cable reported taken a few samples from broken wires on the surface of the strands. Q6.11 Were New Wires Spliced to Replace the Samples? (17 Responses) Respondents stated that in the case of 15 bridges, new wires were spliced to replace those taken for samples. Q6.12 Were New Wires Spliced to Replace Broken Wires? (15 Responses) The returned questionnaires reported five bridges for which new wires were spliced to replace the broken wires where conditions allowed; five bridges stated that the broken wires were not spliced; five reported no broken wires were found, and two provided no response. Q6.13 If Yes, to What Depth in the Cable? (14 Responses) Those replying regarding the depth to which they replace wires ranged from 1 inches (about five rings) to 2 inches (about 10 rings). Two bridges only replaced wires on the surface and one bridge had no response.

23 Q6.14 Describe the Method Used to Tension New Wires? (17 Responses) Twelve respondents stated that a new wire was inserted with a pressed-on ferrule at one end and a pressed-on turnbuckle on the other end. Holding on to the two wire ends, a come-along was used to tension the wires to the desired load so that the installed turnbuckle could be tightened. The tension was also checked by recording the deflection of the wire under a fixed load over a fixed length. Five respondents did not answer the question. Q6.15 Method Used to Inspect and Evaluate the Condition and Strength? (21 Responses) All but two respondents answered this question. Of the remaining 19 bridges, one reported using a method that predated NCHRP (though an upcoming inspection was to use NCHRP), and the remaining 17 bridges used NCHRP. Two of the 17 bridges used both the NCHRP and the BTC method. Three of the four helical strand bridges stated they used NCHRP with modification for their cable inspection. Q6.16 If NCHRP Was Used Are There Any Suggestions or Recommendations? (3 Respondents) Three respondents, some owning multiple bridges, offered up the following suggestions: 1. Better define the inspection frequency and number of panels to open based on past inspections and condition findings. Incorporate any appropriate NDE methods. Consider level of maintenance, or changes in maintenance methods. Determine how dehumidification affects inspections. Expand the suspender rope inspection guidelines. 2. Need to include the details of inspection and strength evaluation of the main suspension cable that consists of the helical structural strands. Need to specify adequate NDT methods to detect in situ corrosions and wire breaks. 3. The third group of respondents from the owner of multiple suspension bridge offered the following: Cable Inspection, Sampling and Testing a. Consider length of cables when determining number of panels to be opened. Does it make sense to open the same number of panels on a small/short bridge as on a big/long bridge? If different bridges have fewer/more panels (or length of cable), why open the same number of panels? Might the number of openings be a percentage of the number of panels (or length of cables)? Every bridge cable (s) is unique as to the cable length, diameter, number of cables and wires, their condition, maintenance and inspection history, propensity for corrosion and level of deterioration, types of corrosion, propensity for cracked wires, number of broken wires, etc. The inspection plan must take these and other considerations into account and develop a recommended inspection program that is specific to the bridge and its cable(s). This would avoid opening up more panel points than necessary as it is unknown what harm cable openings may cause to long-term cable performance. b. Evaluate sample sizes. (Table 2.4.3.5.1-1). If the sample mean calculations are eliminated it may result in needing a different sample size where a smaller sample sizes can be used. Correlation to be developed for the number of wire samples to be taken vs. the cable wire condition found upon cable opening. If no wire breaks are discovered wire sampling requires cutting and splicing unbroken wires. This results in splicing back wires with some uncertainty as to the performance of a spliced wire and may be causing more harm to the cable. If numerous broken wires are found, then sampling of such wires limits the harm to the cable as they must be spliced. However, if no broken wires are found the number of wires to be cut and removed for sampling must be carefully considered so as to minimize cable wire damage. c. The current practice of wire sampling should be revisited and the use of statistical methods to improve the current wire sampling protocol should be considered. d. Wire sampling from interior of cable: Most samples come from the outer few layers of wires due to practical limitations on access. Recommend the collection of information from different owners

24 on methods used for wire cutting and wire repair for the interior wires in order to come up with a recommendation on how to utilize more wires from the interior of the cable in the wire sampling. e. Evaluate the inspection intervals (Table 2.2.4-1). 5 years between internal inspections is short. Consider including the safety factor and adding acoustic monitoring system at this level of corrosion. f. Consider adding safety factor as a criterion for scheduling the next opening. (Table 2.2.4-1). Why base the next scheduled opening on the level of corrosion? The level of corrosion doesn’t determine the safety factor (i.e. strength of the bridge). The capacity of the cable and the load (demand) on the cable encompasses both aspects unique to each particular bridge and should be considered when deciding the timeframe for the next cable opening. g. Include inspection methodologies for anchorage strands. The strength calculation for the anchorage splay have specific issues that are not covered by the report. For example, how does a broken wire effect a full strand, vs. a half strand, vs. a quarter strand? h. Address suspension bridges with four cables. Inspection and sample selection is based on “per cable”. Does the same hold true for bridges with four cables? Can the quantity of panels to be wedged *per cable* be reduced when the number of cables is increased? i. Conduct independent inspections. To measure the sensitivity of the inspection and calculations due to human objectivity, an experiment could be done by using two set of independent inspectors for a panel. The two sets of inspectors shall also independently rate the specimens before testing. This will help determine if there is an effect on the inspection subject to human objectivity. j. Conduct two sets of inspections with two sets of wedge lines. To evaluate the extrapolation practices, inspect eight wedge lines, then re-drive the wedge lines a few degrees (and only a few degrees) off the previous wedge line. This will gauge the sensitivity of the inspection results as a factor of the specific location of where the wedge line is driven. This is important to determine if changes from one inspection to another are the result of actual changes in cable condition or just change in the precise wedge line location. k. Evaluate/Compare results for bridges inspected since NCHRP 534 was implemented. Evaluate/Compare results for bridges inspected since NCHRP 534 was implemented. Possibly also compare to results from pre-NCHRP analyses. Cable Strength Evaluation a. Recommend the re-evaluation/further development of the methods used for cable strength evaluation to better account for variations between corrosion grade and ductility using statistical methods. b. The way the percent cracked wires determined from the sample population generally leads to an overestimation of the percent cracked wires, which leads to an overly conservative estimation of cable strength. c. Redevelopment length needs to be revisited, from experience it appears that a broken wire redevelops its full capacity sometimes within the cable panel point, and certainly at the nearest cable band. d. Fix calculation formulas that are incorrect. (4.3.1.1-1 & 4.5.2-4). A couple of formulas appear to have incorrect operation symbols (+/-). e. Reevaluate the calculation of the lowest strength of a wire (4.4.3). There has been some experiments that have indicated that a longer piece of wire might break at a lower level than the lowest break value of its smaller pieces. This conclusion is not fully understood or conclusively proven. However, the Guidelines tries to capture this by finding the lowest breaking value of a wire by using a distribution to define the minima of the distribution as the hypothetical minimum breaking strength. The strength of a longer wire should be further tested. Current practice might be overly conservative and demands lots of sample wires, it might be sufficient to assume that a wire breaks at its weakest point as a chain breaks at its weakest link. Experienced inspectors should be able to find the worst