Field Inspection of In-Service FRP Bridge Decks (2006)

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PART II: REPORT

SUMMARY: REPORT After the Cold War, the technology transfer initiatives taken by the federal government to use the unused manufacturing capacities of composite manufacturers in the military and space industries resulted in the proliferation of fiber reinforced polymers (FRP) usage in the bridge industry. Some of these companies capitalized on the potential of the transportation market and were instrumental in advancement of FRP use on bridge structures. Since the 1990s, numerous bridges with FRP decks have been built in the United States, and the number of such bridges is continuously growing as bridge engineers become comfortable with the material and its performance. However, most of these bridge decks have been built using proprietary and/or experimental systems and details. The lack of standardization has been a challenge to bridge engineers, who traditionally are accustomed to standard shapes, sizes, and material properties. In addition, variations in the design and composition of FRP decks have resulted in unique problems and maintenance issues associated with each type, further complicating the upkeep of these decks. As the usage of FRP decks becomes more widespread, the state DOTs will need to have guidelines and uniform standards to inspect, assess, and evaluate the condition of their in-service FRP deck bridges. This study was undertaken to help state DOTs and other bridge owners assess the condition of FRP bridge decks in their inventory. This study’s goals are (1) to develop recommended uniform guidelines for the inspection and condition evaluation of in- service FRP bridge decks and (2) to develop a course to train bridge inspectors in the methods for inspecting FRP bridge decks. The study is based on state-of-the-art knowledge of FRP material and decks, ongoing research, experiences from state DOTs’ experimental FRP deck projects, experiences of the defense and aerospace industries with use of FRP materials, and the state of current practice in the use and assessment of this material in the United States and abroad. The manual and course target the practicing engineer or inspector, and the content and organization of the manual are devised to supplement the existing bridge inspection manuals and courses offered by FHWA. The research team completed Tasks 1 through 10 of this research project in accordance with the research plan. This final report documents the project and its significant milestones and contains required project deliverables. The appendixes compiled during the report’s technology review are available online at trb.org/news/blurb_detail.asp?id=5905 (see p. 163 for a list of appendixes). 124

CHAPTER 1 INTRODUCTION AND RESEARCH APPROACH The objective of NCHRP Project 10-64, “Field Inspection of In-Service FRP Bridge Decks” (initiated by the project research team on April 24, 2003) was to develop a recommended manual and an inspector’s training course for field inspection of in-service FRP bridges. Currently, there are no uniform standards or guidelines for field inspection of in-service FRP bridge decks. As the usage of FRP decks becomes more widespread, state DOTs will need uniform standards to inspect, assess, and evaluate the condition of their in-service FRP deck bridges. This project endeavored to add to current knowledge on FRP decks in order to develop a uniform approach to inspecting, assessing, and evaluating them. The project was accomplished through successful execution of 10 tasks outlined in the project statement. The final report presented herein documents the research program. 1.1 BACKGROUND Historically, composite materials—FRP in particular—have been used extensively in many areas, ranging from highly complex aerospace and military applications to more routine applications such as liquid storage tanks, fishing rods, and truck bedliners. Due to their low weight, high strength, and significant durability advantages, the most prevalent nonconsumer use of FRP material has been in the military aviation and civilian space applications. Although the defense and aerospace industry readily adopted composite materials in the 1960s, it took another 20 years before the bridge industry adopted them as viable alternatives to traditional materials. One of the earliest uses of FRP materials in a U.S. bridge superstructure commenced in 1994, when Lockheed Martin designed, fabricated, and tested a 30-ft-span, all-composite FRP bridge (1). The design effort and subsequent testing program lasted 1 year, and the bridge was eventually installed on a private road at a federal facility in Idaho; instrumentation, testing, and evaluation continued on the bridge. However, the first all- composite-superstructure vehicular bridge on a U.S. public road was installed in 1996 in Russell, Kansas (2). Several small-span all-composite bridges have since been built in other states, but the use of all-composite structures has been experimental, and limited to small bridges on lightly traveled rural roads. On the other hand, due to its significantly lower weight and inherent durability advantage over traditional materials such as reinforced concrete, FRP is seeing wider acceptance and use in relatively less critical but maintenance-intensive and dead-weight-sensitive components such as bridge decks. 125 Field Inspection of In-Service FRP Bridge Decks: Report

The number of FRP-decked bridges is continuously growing as bridge engineers become more comfortable with the material and its performance. The lack of standardization, however, has been a challenge to bridge engineers, who traditionally are accustomed to standard shapes, sizes, and material properties. In addition, variations in the design and composition of FRP decks have resulted in unique problems and maintenance issues associated with each type, thereby further complicating the upkeep of these decks. Most studies and research to date have been focused either on understanding the behavior of FRP decks or on verifying and monitoring in-service performance (3–8). However, increased usage of FRP decks will require uniform standards for inspection, assessment, and evaluation of these bridge components (9). In the developmental stages of FRP bridge technology, load testing and dynamic response (modal) testing have been used for assessing the condition of FRP decks. Although these methods provide important condition-related information, the information is global in nature and does not provide clues to potential future problems. The relative complexity of the FRP material and its deterioration modes that—unlike those of conventional materials—do not necessarily provide visual clues make the inspection and assessment of FRP decks even more difficult. It was thought that inspection protocols for bridge decks could be drawn from the aerospace industry, which has made extensive use of FRP composites for decades. However, there are fundamental differences in inspection and maintenance philosophies between the aerospace and highway transportation sectors. Aircraft structures are normally inspected and maintained daily, whereas highway bridges are inspected every 2 years. The differences in inspection frequency and a much more wear-prone application on a bridge make it difficult to use directly the design, inspection, and maintenance philosophies from defense and aerospace industries. In addition, bridge engineers and inspectors are accustomed to working with less fragile materials such as steel and concrete, which show distinct visual clues when they are damaged or deteriorated. Although signs do exist for FRP material condition, the bridge inspectors acquainted with traditional materials have yet to be indoctrinated, and the visual clues are not yet cataloged or adapted for use by the bridge engineering community. As identified by Mertz et al. (9), a “lack of easy and reliable inspection and repair procedures” therefore necessitates development of simple indicators and procedures comparable with those that practicing bridge engineers and technicians now use for conventional materials such as steel and concrete. 1.2 NCHRP PROJECT STATEMENT AND RESEARCH TASKS To address the need for practical guidelines in the inspection and assessment of FRP decks, NCHRP developed the following project statement for Project 10-64: Guidelines and recommended field procedures for inspection of in-service fiber reinforced polymer (FRP) bridge decks are needed. Inspection and monitoring of FRP structures varies widely, from no monitoring, to visual Field Inspection of In-Service FRP Bridge Decks: Report 126

127 Field Inspection of In-Service FRP Bridge Decks: Report inspection, to experimental NDE techniques. The criteria for field inspection should be based on identification of critical components of FRP decks and determination of critical accumulated damage thresholds in those components. Modal analysis, global inspection techniques, and remote monitoring are already being employed on FRP structures for overall condition assessment. An emphasis on techniques for point damage detection is needed. Other inspection issues include accuracy and reliability requirements for inspection data, continuous versus periodic data collection, depth and frequency of inspection, reliability requirements for equipment and sensors, and calibrating the guidelines with field project data. In addition, the type of inspection data collected and the recording format varies. As a consequence, it is difficult to compare one project to another. Thus, there is a need for a standard inspection reporting format to make such comparisons possible. Comparative data would also help the composites industry to refine the technology to better meet the states’ needs. The objective of this project is to develop recommended field procedures, evaluation guidelines, and reporting standards for periodic inspection of in-service FRP bridge decks. A training course for FRP bridge deck inspectors shall also be developed. The project was conducted through execution of the following 10 tasks: • Task 1: Prepare an assessment of performance data, research findings, and other information to determine the failure modes and serviceability problems of FRP bridge decks. Catalog critical details, damage types, and the accumulated damage thresholds for each type of FRP bridge deck. This information shall be assembled from technical literature and from unpublished experiences of engineers, owners, fabricators, and others. • Task 2: Describe the state of inspection practice for FRP bridge decks and identify applicable FRP inspection procedures from other industries. The applicability and effectiveness of visual inspection procedures should be thoroughly evaluated. Documented field performance, especially as it relates to predictions based on the results of current inspection practices, is of particular interest. Field procedures, evaluation guidelines, and reporting standards shall be assessed for speed and economy of use, and for their suitability for integration into the states’ bridge inspection programs. • Task 3: Determine suitable inspection procedures for each critical detail, damage type, and deck type identified in Task 1. With an emphasis on point damage

detection, select procedures from those identified in Task 2 based on technical, operational, and economic criteria. Document and justify the reasons for these selections. Clearly identify details, damage types, and deck types for which no suitable inspection procedures exist. • Task 4: Prepare a detailed outline of an inspection manual for FRP bridge decks. The outline shall include recommended record keeping requirements, relevant data items, and a proposed inspection report format. • Task 5: Submit an interim report that documents the results of Tasks 1 through 4. Following project panel review of the interim report, meet with the panel to discuss the interim report and the remaining tasks. NCHRP approval of the interim report will be required before proceeding with the remaining tasks. • Task 6: Develop a draft inspection manual based on the approved outline. The manual shall be prepared in the format used in FHWA’s Safety Inspection of In- Service Bridges: Participant Notebook (10). • Task 7: Develop an instructors guide and appropriate training materials for a course on field inspection and documentation of the condition of FRP bridge decks. • Task 8: Revise the inspection manual, the training guide, and training materials consistent with panel comments. • Task 9: Plan and conduct a pilot training course on FRP bridge deck inspection. The NCHRP will select course participants and provide the facility for the course. The contractor will be responsible only for the cost of training materials and training staff. • Task 10: Submit a final report documenting the research effort. The inspection manual, training guide, and training materials, revised to reflect comments from the pilot training class, constitute appendixes to the report. 1.3 RESEARCH APPROACH In accomplishing the project objectives, the research team believed that adaptation of accumulated inspection experiences and well-served practices from other industries and countries would provide the maximum return for the bridge engineering community. Lessons learned over the past 50 years from the design, inspection, maintenance, and repair of FRP composites in the defense and aerospace industries and experiences with FRP usage in the civil engineering practice provided the basis for selecting methods for inspection and evaluation of FRP bridge decks. In particular, the research team accomplished the project objectives by implementing tasks described in Section 1.4 of this chapter. Field Inspection of In-Service FRP Bridge Decks: Report 128

129 Field Inspection of In-Service FRP Bridge Decks: Report The research team conducted a complete technological review to identify the variety of FRP bridge deck problems and their causes. Emphasis was given to identifying the types and composition of FRP bridge decks, common detailing practices, problems associated with each type of bridge deck, and the likely causes responsible for the various problems. In addition, the research team investigated the range of problems associated with FRP components in other countries and industries and identified tested and widely used methods to detect and rectify these problems from the U.S. defense and aerospace industries and in the bridge industry in the United States and abroad. In parallel with the published literature and technology practices research, the research team collected first- hand information, via surveys, on the inspection and evaluation practices and experiences of owners, maintainers, and inspectors of FRP bridge decks. This two- pronged approach allowed the research team to concurrently identify the spectrum of problems and issues associated with FRP bridge decks and to detect potential practices that would be most beneficial for inspection of FRP bridge decks. Based on these findings, an inspection manual and inspectors’ training guidelines were developed. 1.4 RESEARCH TASKS The project team has accomplished the following research activities and objectives. The following activities were conducted by the Research Team under each task as listed. • Task 1: Prepare an assessment of performance data, research findings, and other information to determine the failure modes and serviceability problems of FRP bridge decks. – A literature search was conducted to acquire reports, papers, guidelines, and other information about FRP material and FRP bridge decks (for a listing, see Appendix 1: List of Reviewed Literature). The literature was collected from various sources including the Transportation Research Information Service (TRIS), the Portland Cement Association libraries, FHWA electronic documents, websites, conference proceedings, and others. A databank was created to systematically store the literature search data. In addition, more than 100 electronic documents (reports, manuals or guidelines, and papers) have currently been acquired and saved in a database. The literature search is structured into the following three areas: FRP decks and other civil engineering FRP components. The literature includes information on design, construction, inspection, instrumentation, laboratory testing, and load testing of FRP bridge decks as well as other FRP bridge superstructure members. The literature collected to date covers experiences with FRP bridge components in the United States as well as Europe and Australia. Limited literature on use of FRP in Japan was discovered and is included in the literature database.

Inspection and assessment of FRP components. Because limited published literature was available from civil engineering applications, the literature in this area was collected from sources and industries such as the military, aerospace, shipbuilding/naval engineering, pipeline, and industrial applications. Damage thresholds and remaining life prediction of FRP components. The literature in this area was gathered from the defense and aerospace industries and addresses the issues of damage and residual strength of FRP composite components. These data served as a basis for development of a rating procedure. – The research team developed a survey questionnaire to obtain unpublished experiences of owners, engineers, fabricators, and maintainers and to obtain specific information on inspection methods and damage types of existing in- service FRP decks (see Appendix 2: Survey Questionnaire). – The team also conducted targeted telephone interviews using the questionnaire as a standard framework. The survey responses have been divided into the following groups: Bridge Owners: Fifteen state DOTs and one county highway department were contacted by telephone: California; Delaware; Georgia; Indiana; Illinois; Iowa; Kansas; Maine; Maryland; New York; Ohio; Oregon; Pennsylvania; West Virginia; and Wisconsin; and Butler County, Ohio. Of the bridge owners contacted, survey questionnaire responses were obtained from Delaware; Georgia; Illinois; Iowa; Maine; Maryland; New York; Ohio; Oregon; West Virginia; and Butler County, Ohio. Bridge plans, details, and inspection records were obtained from Delaware, Illinois, New York, Ohio, and West Virginia. Design plans, inspection reports, and Structural Inventory and Appraisal (SI&A) forms have been obtained on the Muddy Run Bridge in Delaware. Additional information in the form of testing data and construction and inspection photographs are anticipated on this bridge. Design plans, construction photos, connection details, and a project report were obtained on one FRP deck bridge in Illinois. Biennial inspection reports on seven FRP deck bridges were obtained from New York. These bridges include Route 46 (Osceola Road) over Salmon River, Route 52 (Triphammer Road) over Conesus Outlet, Route 223 over Cayuga Creek, Route 248 over Bennett Creek, Route 367 over Bentley Creek, Route 418 over Schroon River, and South Broad Street over Dyke Creek. From Ohio, a detailed inspection report on the Salem Avenue Bridge was obtained. In addition, design plans and inspection reports were obtained Field Inspection of In-Service FRP Bridge Decks: Report 130

131 Field Inspection of In-Service FRP Bridge Decks: Report for the Tech-21 Bridge from Butler County, Ohio. Design and inspection reports on the Hanover Street Bridge were obtained from West Virginia. Bridge Research Community: To obtain unpublished data on the failure modes and in-service performance of FRP bridge decks, a list of universities conducting research in FRP decks was created. This list was expanded through addition of universities and researchers recommended by the NCHRP panel members. The universities contacted by the research team included Georgia Tech, Iowa State University, University of California at San Diego, University of Cincinnati, University of Delaware, University of Maine, University of Missouri, University of Pittsburgh, University of North Carolina, University of Wisconsin, Virginia Tech, and West Virginia University. In addition, the research team contacted FHWA’s Non-Destructive Evaluation (NDE) Center for information on its latest research. The research team has received responses from Georgia Tech, University of North Carolina, and University of Pittsburgh. Manufacturers and Fabricators: The research team created a list of FRP deck manufacturers in the United States and has established contact with all major manufacturers to obtain their perspective on in-service behavior of the FRP bridge decks. International Agencies: The research team contacted and obtained research and policy reports from two international agencies: Centrum voor Lichtgewicht Constructies TUD-TNO in The Netherlands and The Highway Agency of the Department of Transport in the United Kingdom. – Published literature and survey/interview responses were used by the research team to digest information on the current state of the FRP bridge deck inventory as well as the state of inspection practice (for a summary of survey responses, see Appendix 3: Survey Results). – FRP deck types and manufacturers were cataloged, and details of various deck types identified (for a summary of findings, see Appendixes 4: Summary of Installed FRP Decks and Their Damage Inspection, Appendix 5: Connection Details and Critical Inspection Points, and Appendix 6: Damage Types). • Task 2: Describe the state of inspection practice for FRP bridge decks and identify applicable FRP inspection procedures from other industries. – An assessment of the current methods of inspection was made.

• Task 3: Determine suitable inspection procedures for each critical detail, damage type, and deck type identified in Task 1. – A list of potential inspection methods used for inspection of FRP components was created. The inspection methods were gathered from various industries such as aerospace, defense, shipbuilding, pressure vessels, and bridges. The inspection methods’ utility was researched and assessed (for a description and discussion of inspection methods, see Appendix 7: Inspection Methods). • Task 4: Prepare a detailed outline of an inspection manual for FRP bridge decks. – The research team developed an interim inspection manual. • Task 5: Submit an interim report that documents the results of Tasks 1 through 4. – An interim project report was prepared and submitted for review. • Task 6: Develop a draft inspection manual based on the approved outline. – The research team developed and submitted a draft inspection manual. The manual was based on an outline approved by the NCHRP panel. • Task 7: Develop Instructor’s Guide Manual. – The research team developed an instructor’s guide and a comprehensive training course based on the newly developed manual for inspection and evaluation of FRP bridge decks. An instructors’ training presentation was created along with the training course to effectively disseminate the theoretical background and practical aspects of inspection, identification, and evaluation of defects in FRP decks. • Task 8: Revise Inspection Manual, Training Guide, and Training Material Manual. – After review of the submitted material by the NCHRP project panel, the research team revised the inspection manual, the training guide, and training material consistent with the panel comments. • Task 9: Pilot Training Course Manual – On November 15 and 16, 2004, the team conducted a pilot training course on FRP bridge deck inspection for participants selected by NCHRP. The course included hands-on inspection training with FRP deck samples and visual inspection and nondestructive testing (NDT) techniques, encompassing tap testing, ultrasonic testing, and infrared imaging. The participants were trained Field Inspection of In-Service FRP Bridge Decks: Report 132

133 Field Inspection of In-Service FRP Bridge Decks: Report to use the inspection and testing instruments and methods on samples of FRP deck sections brought to the classroom. During the training course, the participants had the opportunity to inspect samples of FRP decks using the various field instruments and assessment and condition evaluation methods described in the training manual. The training course included interpretation of the results and association of the results to the condition assessment and evaluation. – Important feedback from inspector trainee participants was solicited through a survey form and question-and-answer sessions. These comments and additional feedback from the research panel provided direction for additional revisions of the draft inspection manual • Task 10: Submit Final Report along with the Inspection Manual, Training Guide, and Training Materials Manual. – In accordance with the scope of the project, the research team submitted this final report documenting the research effort. All comments of the NCHRP panel up to and including those generated at the pilot training course were incorporated, and the final revised inspection manual, training guide, and training material are hereby submitted, along with the final report. 1.5 REPORT ORGANIZATION The report is organized into four chapters, a reference section, and appendixes. The chapters synthesize observations and findings; the details of the work, reports, manuals and training materials, task products, collected information, and supporting data are presented in the appendixes, which are published online. The specific sections of the report are as follows: • Chapter 1: Introduction and Research Approach. This chapter provides background information on FRP decks and the current state of knowledge about the decks, the issues that necessitated the implementation of this research project, and the approach and scope of the project. • Chapter 2: Findings. This section presents findings from literature search and the survey of FRP deck owners, inspectors, maintainers, manufacturers, and researchers. In addition, this section presents a summary of findings on critical FRP deck details and methods for inspecting FRP decks.

• Chapter 3: Interpretation and Applications. This section presents interpretation of the findings, key issues, applicability of the interpretations to practice, practical considerations, and selection of ideal inspection methods. • Chapter 4: Conclusions. This section presents the conclusions from the research conducted to date and the course of further research that needs to be conducted to accomplish the objectives of this project. Develop a draft inspection manual based on the approved outline. • References for Report and Appendixes. These sections contain the supporting material and other deliverables that form the basis for the content in the chapters of this report. In addition, the appendixes contain detailed sections on inspection of specific types of FRP decks, the inspection manual, and the training guide. Field Inspection of In-Service FRP Bridge Decks: Report 134

135 Field Inspection of In-Service FRP Bridge Decks: Report CHAPTER 2 FINDINGS This chapter presents a summary of the research team findings. The findings are based primarily on a survey of the bridge and FRP community, the literature search, the personal experiences of the research team members, and feedback from bridge inspector trainees attending the pilot FRP deck inspector training session. 2.1 SURVEY FINDINGS As described in the preceding section, a telephone and mail survey was conducted to obtain both factual and anecdotal information from owners, engineers, inspectors, and researchers on their experiences with design, construction, inspection, and maintenance of FRP bridge decks. All state DOTs and many counties that owned or intended to install FRP bridge decks were contacted during this survey. In addition, almost all major FRP deck manufacturers and many research institutions currently conducting research on FRP decks were contacted during this survey. The survey findings are presented in the sections below. 2.1.1 TYPES OF FRP DECKS IN SERVICE The survey found that there are six major deck types in service at the time of the survey. Each of these deck types has unique cross-sectional geometry, material characteristics, manufacturing processes, and behavior. The deck designs are typically proprietary, and each type of deck is manufactured using specialized material and fabrication methods. The summary of manufacturers, deck descriptions, and cross-sectional views of the deck types is presented in Table 2.1.1-1.

Field Inspection of In-Service FRP Bridge Decks: Report 136 Manufacturer Deck Description Number of Bridges Deck Cross Section Kansas Structural Composites, Inc. (KSCI) Sandwich-type deck with top load- bearing skin, bottom sheet skin, and a deep corrugated core. 12 installations; first in 1996, most recent in 2003. Infrastructure Composites, Inc. (ICI) Same as the Kansas Structural Composites deck. 1 installation in United States; also in Europe. Martin Marietta Composites, Inc. (MMC) The DuraSpan deck system consists of a trapezoid cross- sectional piece manufactured by the pultrusion process. A DuraSpan deck is post-assembled to delivered width by bonding unit pieces with epoxy or urethane adhesive. 27 installations; first in 1996, most recent completed in 2004. Hardcore Composites, Inc. (HCI) Hardcore Composites uses various forms of Vacuum-Assisted Resin- Transfer Molding (VARTM ) technology for producing FRP decks. The majority of decks use vertical standing foam boxes as the core and, unlike pultruded decks with fixed patterns and cross sections, the sandwich core pattern in HC decks can vary substantially. 26 installations; first in 1997, most recent in 2002. Creative Pultrusions, Inc. The Superdeck deck is made with pultruded hexagonal sections bonded to form the desired width of deck and, in many ways, is similar to the DuraSpan deck. 9 installations; first in 1997, most recent in 2002. Strongwell, Inc. Strongwell is one of the largest pultruders. Although it does not directly market vehicular decks, many pilot composite bridge and deck projects have used Strongwellís pultruded components. Estimated 3 installations; earliest in 1995 and latest in 2003. Table 2.1.1-1 Common FRP Deck Types

In addition, three other manufacturers or fabricators have provided FRP decks: Fiber Reinforced Systems; Bedford Reinforced Plastics; and Diversified Plastics/Hughes Brothers, Inc. However, for most practical purposes, the six major manufacturers have greater than 95% of the installed base of FRP bridge decks and appear to have established themselves as the suppliers of choice for future installations. 2.1.2 CURRENT CONDITION OF FRP DECK INVENTORY Most FRP vehicular bridge decks in the United States have been in service for a relatively short time, with an average age of less than 5 years. The oldest of these decks were constructed in 1995 and 1996, with a surge in installation activity occurring in 1998 through 2000. Table 2.1.2-1 provides a summary of the temporal distribution of decks installed by the major manufacturers from 1996 through 2004. 137 Field Inspection of In-Service FRP Bridge Decks: Report 1996 & Prior 1997 1998 1999 2000 2001 2002 2003 2004 Total Kansas Structural Composite, Inc. 1 2 5 3 1 12 Infrastructure Composites, Inc. 1 1 Martin Marietta Composites, Inc. 1 2 1 2 8 4 6 3 27 Hardcore Composites, Inc. 2 3 4 7 9 1 26 Creative Pultrusions, Inc. 3 2 2 1 1 9 Strongwell, Inc. 1 2 1 4 Others 2 2 4 3 9 5 10 15 20 8 10 3 83 Number of Decks Installed in Each YearManufacturer Table 2.1.2-1 FRP Deck Construction over the Years in the United States The table demonstrates that although the frequency of FRP deck installations has not been uniform over the years, most of the activity took place in 2000 and 2001 and the average weighted mean of the age of FRP decks is approximately 4 years. Therefore, the FRP deck inventory is expected to be in relatively good condition. However, commonly observed problems or areas of concern noted by bridge owners or practitioners include the following: • Joints between FRP deck panels: Heavy leakage was generally observed at the joint between the FRP deck panels, especially at joint details that did not have special FRP or reinforced plastic strips adhered to the top as well as bottom surfaces of the FRP panels. The leakage typically resulted in corrosion of the steel stringers underneath the FRP deck joints. Inspector attentiveness to panel joints is warranted. • Wearing surface: On several bridges, delamination and debonding of wearing surfaces was noted. Typically, this delamination occurred when thin epoxy

overlays were used instead of conventional bituminous overlays as the wearing surface on the decks. • Haunch supports: There was a concern that the FRP deck may not “sit” solidly on the haunch, creating a gap between the bottom surface of the FRP deck and the top surface of haunch, thereby causing impact between the deck and the haunch due to the passage of vehicles. • Curbs and parapets: When curbs, and occasionally parapets, are connected to the deck, the effect on the deck of impact-related damage to the curbs is an issue of concern. The curbs are typically cast-in-place concrete, with the concrete extending into the FRP deck core along a narrow strip of the deck for the length of the parapet or curb. • Approach joints: Approach joints have been known to be critical areas, often requiring innovative details to bridge the transition from the approach to the deck. Where approach joints connect to the FRP deck, the deck edge is stiffened by filling a narrow strip of the porous core of the deck along the width of the approach. • Deck to stringer/beam connectors: Although shear connectors have been used in many FRP deck installations, the details of these connectors have not yet been studied in detail. In some installations, steel clips are used to connect the FRP deck to steel stringers. The general concern regarding clip connections arises due to lack of understanding on the behavior of these joints in practice. Some universities are conducting research on the composite action and effective flange areas of FRP decks and steel stringers. However, current design practice neglects any composite action between the FRP deck and stringers. • Delamination of deck components: On some deck installations, there has been noticeable delamination of the skin sheets from the deck core. This is of significant concern as delamination of deck components can result in an exponential reduction in the stiffness of the deck sections. • Moisture ingress: There have been situations where moisture and water have seeped into the porous core of the deck cross section. Although the FRP material used to manufacture decks is resistant to moisture attack, seepage and the consequent freeze-thaw could result in mechanical damage to the deck, leading to delamination or cracking of FRP deck components. In summary, due to its relatively young average age, the FRP bridge deck inventory seems to be in good condition. However, there exist some material, fabrication, and detailing issues that are currently affecting the condition of these decks or have the potential to adversely affect the future condition of these decks. These FRP degradation mechanisms serve as the foundation for establishing uniform inspection practice. Field Inspection of In-Service FRP Bridge Decks: Report 138

139 Field Inspection of In-Service FRP Bridge Decks: Report 2.1.3 CURRENT INSPECTION PRACTICE Key observations based on the survey and interview and inspection reports on the current inspection practice are summarized and presented below: • No special inspection guidelines currently exist for inspecting FRP decks. Only New York State DOT has guidelines (i.e., advisory circulars) on use of FRP on bridge structures that specifically identify the special nature of FRP materials (11). However, the guidelines are generally directed toward use of FRP for repair and strengthening of concrete structures. • Some DOTs had requested inspection manuals from the deck manufacturers; however, the quality and content of the manuals varied considerably. In addition, many DOTs have not yet formally accepted the inspection manuals. The research team obtained a more-detailed manual authored by KSCI for three FRP deck bridges in St. James, Phelps County, in Missouri (12). • Most DOTs do not perform hands-on inspection. In most states, the current practice seems limited to visual inspection. • The DOTs typically use the same rating system as used for other conventional bridge components. FRP deck rating is currently based on subjective evaluation of the deck appearance. • No guidelines currently exist for rating severity of observed conditions on the FRP components. • Most DOTs have performed load testing while some have conducted modal testing of FRP bridge decks. The testing is usually conducted during the first year and is generally not repeated over an extended period past the first year to 2 years of service. The metric used to evaluate the load-testing observations compares the deflection of the decks during subsequent load tests; no difference observed during subsequent tests indicates satisfactory performance of the deck. However, there does not seem to be a uniform method to evaluate and pinpoint problems if different observations are recorded in subsequent load tests. • The tap test is used by some DOTs (California, New York, and Ohio), but many inspection teams are unaware of the methods available and necessary for inspection of FRP components. Some of the DOTs use the chain-drag method in addition to tap tests to identify locations of delamination (California and New York). • Thermography, acoustic methods, and laser shearography have been used on an experimental basis on some bridges, mostly under University/DOT joint collaboration programs (University of California San Diego, Virginia Tech, and

University of Delaware). It did not appear that any of these methods are being considered for use in the near future by the DOTs. • Experimental methods such as impact echo, acoustic emission, radar, and other methods are being tested at university research facilities for potential application in the field. 2.2 FINDINGS FROM THE LITERATURE SURVEY A detailed and thorough literature search was conducted to obtain as much published information as possible on FRP material and its inspection, with particular emphasis on literature pertaining to FRP bridge decks. Although substantial literature exists on FRP bridge decks, most of it documents field and laboratory tests that focus on mechanical strength and design-related issues (8, 13, and 14). Some researchers, on the other hand, have conducted research on the durability and environmental stability issues of FRP material as it relates to civil infrastructure use (1, 7). However, most of the research in design, inspection, damage quantification, residual strength, and maintenance of FRP materials has been conducted under the auspices of the defense or aerospace industry organizations. Because FRP materials have been used in U.S. military and space applications for more than 4 decades, considerable information on all aspects—from manufacturing to inspection, maintenance, and repair of FRP components—is available in technical publications issued by the U.S. Department of Defense (15–20). A summary of literature reviewed during the course of this research project and its applicability to the objectives of this project is presented in the sections below. 2.2.1 HISTORICAL PERSPECTIVE ON FRP USE The initial research into advanced material technology evolved from metallurgical sciences. The demands of the military and the space industry for cutting-edge applications in the Cold War era resulted in the development of metal composites in the mid-1950s. The following decade saw rapid developments in the field of material engineering, and the development of high modulus boron and graphite filaments in the 1960s initiated an era of non-metallic composite materials (21). Chemical industry giants such as Union Carbide and DuPont furthered the development and use of composite materials by designing high-strength, high-modulus carbon, glass, and aramid fibers. The Department of Defense, the National Aeronautics and Space Administration (NASA), and the research organizations and private-sector industries that fulfilled their needs were among the first to conduct detailed research into FRP materials. The Department of Defense, NASA, and FAA synthesized the applied research conducted by various organizations and converted it into manuals and circulars to codify and transfer the best practices for use in military and aerospace products. Field Inspection of In-Service FRP Bridge Decks: Report 140

141 Field Inspection of In-Service FRP Bridge Decks: Report Although the defense and aerospace industries readily adopted composite materials early on, it took another 20 years before the bridge industry started considering FRP as a viable alternative to traditional materials. The first civil engineering application of FRP material was a dome constructed in Benghazi in 1968 (22), while the first FRP bridge (pedestrian) was built in Israel in 1975 (21). Since then, other countries have experimented with the use of composite materials in bridge construction (23). Whereas the U.S. aerospace and military industries were leaders in the use of advanced materials, the U.S. bridge industry lagged behind Europe and Japan (24) in adopting the new materials until the 1980s, when FRP materials began to be used in the seismic rehabilitation of bridges. By the late 1980s and early 1990s, the U.S. bridge industry saw many other FRP applications, usually for secondary members on a bridge structure. One of the first uses of FRP materials in a bridge superstructure was in 1994 when Lockheed Martin designed, fabricated, and tested a 30-ft-span, all-composite FRP bridge (1). Design and testing lasted about 1 year, and the bridge was eventually installed on a road at a federal facility in Idaho where field-testing and evaluation continued. This FRP composite deck concept became the basis for designs that are now being successfully produced by MMC. The first all-composite-superstructure vehicular bridge on a U.S. public road was installed in 1996 in Russell, Kansas (2, 22). Several small-span all-composite bridges have since been built in other states, but the use of all-composite structures has been experimental and limited to small bridges on lightly traveled rural roads. On the other hand, due to its significant lower weights and inherent durability advantage over traditional materials such as reinforced concrete, FRP has seen much wider acceptance and use in relatively less critical but maintenance-intensive and dead-weight-sensitive components such as bridge decks. 2.2.2 STATE OF RESEARCH AND TESTING OF FRP DECKS The use of FRP in bridge decks was essentially a result of the technology transfer initiatives taken by FHWA at the end of the Cold War to share and utilize the extensive knowledge base and unused manufacturing capacities of companies traditionally associated with military and space applications. Initiatives by FHWA through the Innovative Bridge Research Program and by other entities interested in furthering the use of FRP in bridge infrastructure resulted in focused study of this material for bridge applications. The research efforts to date have been directed toward developing shapes and sections appropriate for civil applications, developing fabrication methods to manufacture these shapes efficiently, understanding their behavior under simulated vehicular loads, and developing details and methods with which to design and construct FRP decks. This research therefore has focused on the strength and behavior of FRP bridge decks (3, 12), with limited attention directed toward aspects such as serviceability, durability, long- term behavior, post-damage behavior, remaining life, and inspection and maintenance issues. Nearly 100 bridges with FRP decks have been built in the United States since the

1990s, and the number of such bridges continues to grow as bridge engineers become comfortable with the material and its performance. However, most of these bridge decks have been built using proprietary experimental systems and details. The lack of standardization has been a challenge to bridge engineers, who are accustomed to standard shapes, sizes, and material properties. In addition, variations in the design and composition of FRP decks result in unique problems and maintenance issues associated with each type, thereby complicating the upkeep of these decks. Specific knowledge is lacking on issues such as durability, post-damage behavior, unraveling of the composite section, and the effect of environmental factors such as radiation, heat, and moisture. Furthermore, in the absence of well-defined, readily discernible clues to reveal defects and deterioration, indirect means such as load testing have been used to ascertain the adequacy of in-service FRP bridge decks. Bridge owners have undertaken load-testing programs not only to verify the behavior of FRP decks, but also (due to a lack of better condition evaluation options) to ensure that the decks’ acceptable behavior will continue over time (25–28). However, the load-testing method has three main drawbacks: (1) the decks are designed with a large factor of safety, so the risk from potential overload is minimal; (2) the design is typically controlled not by strength requirements but rather by deflection limitations, so excessive loads could cause failure due to large deformations; and (3) the failure, if it were to occur, would be non-ductile. Hence in the long-term, visual, or other complementary indicators also must be evaluated to ensure the safety of the decks. The design assumptions have been verified through load testing and other research, while successive tests of in-service decks have demonstrated that the decks have been behaving as expected. Up to now, and in the absence of better inspection and evaluation methods, successive load testing has provided an indirect method to assess continued good performance of the decks. 2.2.3 INSPECTION AND ASSESSMENT OF FRP COMPONENTS The research on FRP decks has focused mostly on the design, performance, and durability of this material, with limited energy expended on the study of inspection and evaluation methods for these decks (9). The survey of the bridge owners and the literature search revealed that bridge owners have usually requested the deck manufacturer to provide inspection and maintenance manuals for FRP decks as part of deck installation projects. In some cases, manufacturers have prepared inspection and maintenance manuals tailored to the specific bridge details and deck type and submitted them as part of the project deliverables (12). The survey of bridge owners and maintainers showed that, in many instances, the inspection manuals either were not submitted or were not accepted by the bridge owners; and in some instances, the manuals were found to be of limited use for inspection and maintenance of the decks. Some bridge owners have, however, developed advisory circulars or internal memos that recognize the special nature of FRP and provide material-specific guidance to help the practicing engineer, inspector, or maintainer manage the FRP infrastructure. Although Field Inspection of In-Service FRP Bridge Decks: Report 142

143 Field Inspection of In-Service FRP Bridge Decks: Report most bridge owners did not have such memos or guidance documents, two publications by New York State DOT were found to be valuable in this study (28, 29). Unlike the bridge engineering industry, the military and aerospace sectors have used FRP for more than 4 decades. They have conducted extensive research on the inspection and maintenance of this material in order to develop practical procedures that will ensure peak performance of mission-critical FRP components on aircraft and other military structures. They have produced extensive literature on the inspection and evaluation of FRP components in the military and aerospace domains. Although there are fundamental differences in composition, loading, inspection, and evaluation criteria between FRP used in defense or aerospace applications and that used in bridge applications, the basic inspection and evaluation philosophy could be adapted to the bridge industry. Some publications present practical guidelines and insights on inspection of FRP materials (20, 30–33). Military Handbook 793 (20) addresses various inspection methods: visual, acoustic, radiography, ultrasound, and so forth (for detailed discussion, see Appendix 7). Inspection and evaluation practices from other non-defense industries provide additional useful insights and tips on practical inspection procedures that could be adopted for inspection of FRP bridge decks (34–37). In addition, state-of-the-art research on inspection and evaluation methods for FRP material—specifically, FRP civil/structural components—will further the current knowledge on inspection methods and help to develop innovative methods suited for the bridge industry. Currently, such research is being conducted in the United Kingdom (38), at the U.S. Naval Academy (39), and at Virginia Tech (40). Additionally, there are many other useful publications that present current research on feasible inspection or evaluation methods for FRP components in civil infrastructures (41–44). Discussion on the applicability of the various inspection methods, the advantages and drawbacks of the methods, and adaptability of these methods into current bridge inspection practice is found in Chapter 3 (also see Appendix 7). 2.2.4 DAMAGE THRESHOLDS AND REMAINING LIFE PREDICTION In the civil industry and for FRP decks in particular, research is lacking in the areas of damage estimation, damage accumulation, and remaining life prediction. Some research has been conducted to assess the post-damage behavior of FRP decks (45); research in the area of long-term performance and damage accumulation has been restricted to durability testing of FRP material (1, 7), and fatigue testing of decks (46). The research by Lenett et al. (45) studies the effects of damage on the behavior of FRP sandwich deck panels. The research finds that damage, especially delamination, distinctly causes change in the deck stiffness and results in anomalous behavior of the deck. Dutta et al. (46) present results from experimental fatigue testing under extreme temperature conditions of different types of FRP and non-FRP decks subjected to 10 million low-cycle fatigue through simulated HS-20 vehicular load. The research focuses on the long-term behavior of FRP decks and shows that behavior of FRP decks is adversely affected by fatigue as

well as by higher temperatures. These research studies are limited in their scope, however, and do not provide in-depth insights into the post-damage strength and behavior of FRP decks, nor the effect of damage on the serviceability criteria and useful life of these components. Research on fatigue life of composite beams and civil components has been conducted by Senne (47), Tang et al. (48), and others. However, extensive physical research exists in the defense and aerospace industries on damage susceptibility, immediate physical effects of damage, and post-damage behavior of FRP material and components. Military Handbook 17, Volume 3 (17) is a detailed publication that systematically addresses the issues of damage initiation, damage quantification, correlation of damage to strength, and the ideas the Department of Defense adopted to assess damage and its effect on the performance of the FRP components used in military applications. Other publications provide information on damage initiation and post-damage behavior of FRP (49–53). Kan (49) presents results from numerous experimental studies on various composite panels to determine the effect of impact damage on the strength of the FRP panels as well as the residual strength of the impacted panels. McGowan and Ambur (50) discuss experimental studies on the impact damage and residual strength of composite sandwich panels with and without compression loading. The paper presents correlation between the impact magnitude, the type of impact, damaged area dimensions (damage diameter), and the residual strength of the sandwich panel after the impact. Nyman (51) discusses theories and currently used methods for determining damage thresholds in composite materials and enumerates inferences from experimental and analytical studies. The experimental and analytical studies relate to quantification and assessment of damage severity, damage tolerance, and residual strength of composite material used in the development of the new generation of Swedish fighter jet JAS39 Gripen. Tomblin et al. (52, 53) meanwhile present a semi- empirical study of impact damage and fatigue tolerance of sandwich airframe structures and provide methodologies in which experimental data could be used to develop damage evaluation criteria. Extensive studies have also been conducted in the field of analytical assessment and modeling of damage and damage propagation in FRP material. Case et al. (54, 55) provide an excellent discussion on practical issues in developing life prediction techniques for FRP material that are typically used in aerospace applications. There are other significant studies that focus on analytical issues in modeling damage, damage propagation, and remaining life of FRP material (56–60). Although most of the research on damage thresholds and residual strength (i.e., remaining life) has been conducted on thin FRP sheet-type or sandwich-type aircraft materials, the defense and aerospace research provides an excellent starting point for extending or extrapolating the findings and philosophies to FRP decks. Field Inspection of In-Service FRP Bridge Decks: Report 144

145 Field Inspection of In-Service FRP Bridge Decks: Report 2.3 KEY PUBLICATIONS The following publications from the Department of Defense, the U.S. Army Corps of Engineers (USACE), and FAA are promising sources for adapting more than 50 years of industry experience with FRP materials toward bridge engineering applications: • Composite Materials Handbook, Volumes 1 through 5, are military handbooks published by the Department of Defense (15–19). Of particular interest is Volume 3, which covers usage, design, and analysis of polymer composite materials. This detailed and comprehensive handbook covers almost all aspects of composite behavior and provides practical insight on the damage etiology and accumulated damage thresholds of FRP materials. In addition, the handbook provides practical guidelines on identifying defects, damage, and deterioration of FRP components. • Nondestructive Active Testing Techniques for Structural Composites is another military handbook published by the Department of Defense (20). This handbook provides detailed discussion and practical application guidelines for the complete range of NDT techniques—from visual inspection to the more complex nuclear radiography methods—which could be used on FRP materials. The handbook also discusses the reliability of the various methods and provides an in-depth assessment of the techniques, including the correlation of specific NDT methods to type of defects and type of FRP design. • Engineering Technical Letter ETL 1110-2-548, “Engineering and Design: Composite Materials for Civil Engineering Structures,” is published by USACE (33). The ETL compiles and discusses various issues in the use and upkeep of composite materials for civil engineering applications. This 60-page document covers all aspects of FRP material used in civil engineering structures— manufacturing to durability, quality assurance, and inspection and repair. • Advisory Circular AC20-76: Maintenance Inspection Notes for Boeing B- 707/720 Series Aircraft and Advisory Circular AC20-107A: Composite Aircraft Structure, published by FAA (31, 32), provide practical advice and inspection methods for various FRP components of the Boeing 707 aircraft. These circulars, and similar circulars and directives for other aircrafts, provide invaluable practical advice on identifying and appraising damage and defects in structural components made of FRP materials. The practical aspects of the inspection techniques and damage detection and appraisal methods identified in these circulars could easily be adapted for application on bridge structures. • Structures Design Advisory: FRP Decks and Superstructures, an informative advisory circular published by New York State DOT (11), alerts bridge designers and inspectors to the unique characteristics of FRP material and provides guidance on how to work with this material.

• Laboratory and Field Testing of FRP Composite Bridge Decks and FRP- Reinforced Concrete Bridge for the City of St. James, Phelps County, MO, a report published by Missouri DOT (12), includes typical details as well as inspection and maintenance manuals for three FRP bridge decks constructed and monitored within the scope of the research project. • “Inspection of FRP Equipment: When and How to Inspect and What to Look For,” a paper published by TAPPI (37), provides some practical guidelines on inspection of FRP components. • “Fatigue Performance Evaluation of FRP Composite Bridge Deck Prototypes Under High and Low Temperatures,” a paper presented at the 82nd Annual Meeting of the Transportation Research Board in 2003 (46), provides experimental data and inferences from the experimentation to assess the fatigue characteristics of FRP decks. A Master’s Thesis titled “Fatigue Life of Hybrid FRP Composite Beams” and published by Virginia Tech (47) provides some excellent data on fatigue characteristics of FRP beams. “Fatigue Model for Fiber- Reinforced Polymeric Composites in Civil Engineering Applications,” a research report published also by Virginia Tech (48), provides useful data, interesting inferences, and analytic models on the fatigue life of FRP materials used in civil infrastructure applications. • “Simulation of Performance and Life Prediction for Composite Laminates: MRLife12” (55), a software program and its manual published by Virginia Tech, provides an excellent discussion on developing analytical residual strength or remaining life models based on experimental data and analytical concepts. Enhanced Reliability Prediction Methodology for Impact Damaged Composite Structures, published by FAA (49), provides data on strength reduction due to various types of damages on various types of FRP materials. The data from this research could be useful to devise a statistical semi-empirical method that other industries could use to gage the severity of damage and its likely effect on the material’s post-damage performance. Field Inspection of In-Service FRP Bridge Decks: Report 146

147 Field Inspection of In-Service FRP Bridge Decks: Report CHAPTER 3 INTERPRETATION AND APPLICATIONS This section presents interpretation of the findings, key issues, applicability of the interpretations to practice, practical considerations, and selection of ideal inspection methods. 3.1 ISSUES WITH DESIGN VARIANTS The large variability in types of FRP decks and the lack of standardization in deck shapes, material composition, manufacturing processes, design methods, and details are important issues that affect the inspection, maintenance, and management of the FRP deck inventory in the United States. Since FRP is a “designed” material, its characteristics are significantly affected by parameters such as the composition and layout of its constituent parts, manufacturing processes, shapes of the cured FRP subcomponents, the process used in assimilation of subcomponents, and the geometry of the final deck cross section. Therefore, changes in any of these parameters can create innumerable types of FRP decks, each with distinct characteristics and associated strengths and weaknesses. This variety of FRP deck types raises several key issues that are relevant to the current study. These issues are briefly discussed below: • Difficulty in establishing a uniform quality and performance standard for FRP decks: Due to the variety of materials and manufacturing processes, it is difficult to establish uniform quality and performance standards for the FRP decks. Each “type” of deck differs from the others in its constituent materials, subcomponents, and method of manufacturing, leading to variations in achievable quality, consistency of quality, and the performance and behavior of the decks. For example, the consistency and quality achievable through the pultrusion process is reportedly much higher than that achievable through the hand lay-up process. Similarly, the type of component materials used—that is, the fiber and the resin—and the cross-section geometry—for example, sandwich- type with vertical corrugated core, bonded pultruded sections, and so forth—will significantly affect behavior and performance. • Potential for variability in types and location of critical details: Due to variability in the internal construction of FRP decks, there is considerable latitude for variability in the location of critical details. For example, in sandwich panels, critical locations that can show delamination or separation are typically at the

core–to–face sheet connections while in pultruded sections, the critical locations could be at joints between each pultruded subcomponent. In addition, the corrugated core in some sandwich-panel decks is bonded to the face sheets along thin edges, creating potentially weak areas that can easily separate due to poor adhesion or load-deflection effects. • Potential for superfluous changes leading to development of newer deck designs: Without established guidelines, designers and manufacturers have the freedom to vary any aspect of FRP material, section, or manufacturing method. This can result in development of superfluous variations in deck type, each slightly different from the other and each with different performance and behavior patterns. This practice could result in unnecessarily large variety of decks without any real benefit in terms of better design or performance, leading to difficulty in maintaining or managing such deck inventory. • Difficulty in expeditiously assimilating and distributing critical information about new design should be anticipated: Although it is possible to catalog critical areas and peculiarities of each given deck, each new deck type introduced into the bridge inventory will require careful evaluation and study by the bridge owner to identify the critical details and vulnerable areas in the new deck type. In addition, this ever-changing information will have to be collected, analyzed, composed, and disseminated at regular intervals to practicing engineers, inspectors, and maintainers in order to keep them up-to-date on the vulnerabilities and issues of each deck type. • Inadequate testing and performance assessment: The research team feels that the ease with which deck types can be changed may lead to creation and installation of future FRP decks without the rigorous testing and assessment that is now common. Such inadequate testing and assessment could result in installation of decks whose behavior is not clearly understood and whose critical details or vulnerable locations are not clearly identified, potentially causing serviceability and safety problems in the future. 3.2 ISSUES WITH CURRENT INSPECTION PRACTICE The current inspection practice ranges from no inspection of the FRP deck to detailed inspection that includes visual inspection, tap testing, load testing, modal testing, and thermography. Among participants in the bridge owner group, the survey found limited awareness of the FRP decks’ uniqueness or their need for special methods and activities for inspection and maintenance. Some survey participants were unaware of the need to check for simple visual clues such as discoloration or cracking or acoustic clues such as hollow sounds to detect delamination. From the survey, it appears that most personnel involved with the design of FRP decks appreciated the need for addressing special inspection and Field Inspection of In-Service FRP Bridge Decks: Report 148

149 Field Inspection of In-Service FRP Bridge Decks: Report maintenance issues regarding such decks; however, personnel not involved in the design and those responsible only for deck inspection or maintenance seemed to consider these decks similar to conventional concrete decks in their inspection and repair needs. Very few of the survey participants seemed to employ FRP deck–specific inspection methods while inspecting their FRP deck inventories. Most survey participants from the academic and consulting group and some from the owner group were aware of the FRP decks’ uniqueness and their need for special methods for inspection, assessment, and maintenance. Many among these survey participants were aware of more-detailed inspection methods such as ultrasonic, radiographic, and thermographic methods. It was also discovered that some of these nonstandard techniques, such as ultrasonic and thermographic methods, were being evaluated through joint owner-academic research projects. Based on these findings, the research team sees a clear and definite need for education and training of bridge inspectors and maintainers as to the unique nature of FRP decks and methods to inspect and evaluate these decks. 3.3 CLASSIFICATION OF SIGNIFICANT DETAILS Given many types of bridge decks—each with distinct material characteristics, fabricating methods, cross-sectional details, and performance characteristics—the research team recommends organizing the inspection instructions by the deck or manufacturer type. Because critical areas and inspection methods differ for each deck type, it makes practical sense to organize the data by deck types. Doing so serves two purposes: (1) it makes it easy for inspectors to select an appropriate checklist of details to inspect and (2) it allows inspectors to choose appropriate inspection methods and evaluation criteria. For each deck type, an ideal method to organize the data for inspection and evaluation of the FRP decks is by dividing the deck details into two major categories: those associated with the deck cross section and those associated with bridge geometry and connections. • Category 1: Details within the deck cross section: Significant details in this category include those that are associated with cross-section design, material, manufacturing, and fabrication of deck panels. The significant details within this category generally depend on the material components, manufacturing and fabrication process, and cross-section composition of the deck. • Category 2: External details and connections: In this category, details related to entities external to the deck cross section are included. Some of these entities include wearing surfaces, connections between deck panels, connection of deck panels to the superstructure and substructure, and connection details of the parapets and railings to the deck or other superstructure elements. The significant

details in this category are not necessarily associated with a specific type of deck, but are more globally applicable. Various commonly observed damage types associated with these significant details have been identified (see Appendixes 4–6). The damage types are organized first by deck types and then into the two categories identified above. In addition to cataloging the damage types, an attempt has been made, where possible, to correlate the damage type to the type of loading or affecting medium that may have contributed to the cause or exacerbation of the damage. The common causative agents for most damage types included type of loading, restraint conditions, impact effects, and fire and temperature effects, among others. (For a summary of the findings, see Appendixes 4–6.) 3.4 INSPECTION METHODS, THEIR APPLICABILITY, COSTS, AND OTHER ISSUES Inspection methods that could be used for FRP decks were identified from the realms of aerospace, defense, shipbuilding, pressure vessels, and bridges. (See Appendix 7 for descriptions and discussions of inspection methods and inspection cost data.) Some of these methods, such as visual or UT methods, are similar to those used currently in bridge inspection. Other methods such as acoustic, laser shearography, radiography, thermography, and so forth are more complicated and seldom used in current bridge inspection programs. In Table 3.4-1, the various inspection methods are presented in order of complexity and usefulness and are correlated to the types of defects or deck components that these methods assist in detecting. Field Inspection of In-Service FRP Bridge Decks: Report 150 Technique Visual X X X X Mechanical Impedance (Tap Test) X X X X X Thermal X X X Ultrasonic X X X X Acoustic Emission X X X Radiographic X X X X Laser Shearography and Other X X X X Fe at u re s an d An om al ie s Ex te rn al El em en ts Im pa ct Da m ag e Fo re ig n M at te r Co re or In te rn al El em en ts Di sb on ds De la m in at io n s Cr ac ks Table 3.4-1 Inspection Method Applicability for Specific Defects and FRP Deck Features (20)

151 Field Inspection of In-Service FRP Bridge Decks: Report The visual method is by far the most important and simplest technique for inspection of FRP decks. Even in the aerospace and defense industries, inspectors rely on the visual technique for detecting in-service problems. Visual inspection allows the inspector to rapidly detect gross imperfections or defects such as cracks, delamination, or impact damage. Visual inspection often can aid in detecting other imperfections such as porous adhesive fillets, lack of filleting, lack of adhesive, edge voids, discoloration, deformation, and other imperfections. To a trained inspector, the visual technique provides immediate clues, and this method serves as the mechanism for identifying areas that should be inspected through other more-detailed and complex methods. Although this technique is operator-interpretive, it is of such significant value that the inspectors should be trained to know what they are looking for and what any variation might mean to the strength and reliability of the component. The visual method, however, has two drawbacks: (1) it does not lend itself to quantifying the extent of damage and (2) components within another component or not directly visible can not be inspected by this method. Tap testing is another excellent and easy method for inspecting FRP decks. The tap test allows the inspector to notice changes in sounds emitted while tapping FRP surfaces. Although this method lends itself more readily to inspection of sandwich panels, it can nevertheless be used on pultruded sections, albeit with lesser degree of effectiveness in detecting delaminations or debonds. However, most common problems on FRP decks can be identified by using the tap-test method in conjunction with the visual technique. Neither of these techniques requires any specialized equipment, and both are easy to incorporate into a bridge owner’s inspection program through training in inspection of FRP components. On the other hand, some of the other techniques listed above are much more complex, are significantly more costly and time-consuming, and require special expertise in conducting the tests and in interpreting the results. Except for thermography, most of the specialized methods are useful only for inspecting small areas due to cost and operational reasons. Therefore, these methods are more practical for detailed assessment of potentially damaged or defective areas that have already been identified by either the visual or the tap-test methods. Of the various advanced methods, thermography and UT appear to be most practical in terms of their applicability and adoptability in a bridge owner’s inspection program. Bridge engineers and inspectors already familiar with UT equipment and technique would find it easy to adapt this method for use on FRP decks. The thermography method also could be readily adopted into an inspection program because it is somewhat easier to use, does not require very expensive equipment, and provides output that can be visually analyzed. The other techniques, such as radiography and shearography, are more costly and often require expensive specialized equipment and considerable training to operate the equipment and interpret the results. Hence, these other techniques, although useful and applicable, appear less likely to be incorporated into the current bridge inspection programs.

3.5 DETAILS AND DESIGNS THAT WILL BE DIFFICULT TO INSPECT As discussed in the previous section, numerous methods are available to inspect critical details and detect defects or damage in FRP bridge decks. The research team feels that visual and tap-test methods can provide satisfactory results in detecting defects and damages at most locations on FRP decks. Specific areas identified by the visual or tap test techniques that require further in-depth investigation can then be inspected using advanced techniques such as thermography, radiography, or UT. Although some of these methods detect damage that generally cannot be detected by visual or tap-test methods, they cannot necessarily detect damage in every location on the deck. In some areas of the deck, none of the current methods is effective in detecting and assessing the extent of damage. Based on evaluation of all the in-service FRP decks, it appears that some Category 1 details, such as the core or the web elements, are the most difficult details to inspect. Due to the nature of the deck cross section and the layout of deck sub-components, the region of deck cross section between the top and bottom surfaces or face sheets is not visible for visual inspection. Although the tap test can detect damage such as delaminations or disbonds, this detection is limited to areas close to the top and bottom surfaces of the decks; in most cases, even the top surface of the deck is not accessible due to the presence of thick overlays. Among the types of defects, disbonds between the core and the top face sheet in sandwich-type decks are probably the most difficult to detect. Based on findings on the Salem Avenue Bridge, it appears that the core–to–face sheet connection in sandwich- panel decks is vulnerable to disbond due to the small edge area along which the core section is adhered to the face sheets. Even advanced methods like radiography are probably not effective for detecting this defect unless the X-rays are taken in the horizontal plane and in proximity to the defect. Any defect in the core that would be visible to a radiograph in the plan view would therefore be easier to detect than a defect that would be visible in a cross-sectional view. In the case of core–to–top face sheet disbond, modal testing methods or other methods such as impact echo or impulse response may provide a solution in detecting such damages. In pultruded decks, web and flange (top and bottom surfaces) are created concurrently in the pultrusion process, and the sections do not have any discontinuity between the core elements (or web elements) and the flanges. Also, since pultrusion is an automated process, the quality of the pultruded product is likely to be uniform and consistent as compared with sandwich construction in which semi-automatic or manual processes typically are used. Thicker elements and robust sections in this type of deck, however, make it less responsive to tap tests. In addition, this type of deck has similar inspectability issues as the sandwich decks except that the likelihood of defects in this type of deck could be better controlled as compared with sandwich decks. Although there are some significant details in FRP decks that seem to create inspectability issues, the research team feels the existence of any such damage or defect Field Inspection of In-Service FRP Bridge Decks: Report 152

153 Field Inspection of In-Service FRP Bridge Decks: Report would lead to other signs such as larger deflections, discolorations, dimpling, stretch marks, and so forth that would alert the inspector to the existence of problems. (Further discussion on significant details, inspection methods, and difficult-to-inspect areas of each of the major deck types is presented in Appendixes 4 and 7.) 3.6 INFERRING AND INTERPRETING INSPECTION RESULTS Inferring and interpreting inspection results is one of the most important aspects of productively using inspection data to ensure safety and serviceability of inspected components. In the case of FRP bridge decks, once the damage or defects are identified and categorized, they will have to be evaluated and assessed based on some form of uniform rating system. The research team believes that for Category 2 significant details—which include connections, overlays, joints, and so forth—of the assessment could be made using a hybrid method that draws on guidelines used for conventional bridge components combined with those for FRP elements. However, for Category 1 significant details—that is, details internal or intrinsic to the FRP deck cross section—of a system will have to be developed that will correlate observed damage to reduction in remaining life of the components. Although it is difficult to quantify the somewhat subjective inspection data from visual observations or acoustic tests, the aerospace and defense industries have developed methods to quantify some of these results. Based on the type of defect and magnitude of damage, the severity and potential for failure due to the damage are evaluated using a uniform scale in military and aerospace applications. This approach to evaluating damage on composite aircraft structure and components is based on extensive experimental and theoretical studies. For example, one of the charts developed from these studies (17, Figure 7.3.2 [a]) is reproduced below in Figure 3.6-1. As observed in Figure 3.6-1, the chart allows one to correlate the extent of damage (diameter of hole or extent of delamination, etc.) to the reduction in load-carrying capacity of the components, thereby allowing for a systematic evaluation of damage with respect to the reduction in strength. Although the chart is designed for aircraft structures, it shows that a workable systematic approach does exist for assessment of FRP field inspection data. It should be noted, however, that these charts in the military handbooks and other aerospace references have been developed from more than 50 years of research, testing, and development, and it is unlikely that similar charts could be developed for the bridge engineering industry within the scope of this project. In addition, aircraft structures are inspected at very high frequency, typically before and after each flight. However, it is possible to borrow the idea from the defense industry to establish a long-term goal of developing similar charts for the bridge industry.

The research team developed a semi-empirical method that would assist an inspector in evaluating and assessing the damage and deterioration based on some uniform or standard scale. This correlation of damage or deterioration to remaining life either could be set arbitrarily or could be devised using some of the test data from aerospace applications. For example, for a specific type of deck, the extent of damage quantified by the delaminated area could be related to specific reduction in strength. The scale was set such that at one end, for no delamination, there would be no reduction in carrying capacity of the deck while a delamination diameter of twice the deck thickness or half the clear span of the deck could be attributed to loss of, say, 50% of the strength. Field Inspection of In-Service FRP Bridge Decks: Report 154 Figure 3.6-1 Damage versus Strength Reduction (17, Figure 7.3.2[a]).

155 Field Inspection of In-Service FRP Bridge Decks: Report CHAPTER 4 CONCLUSIONS The research conducted under NCHRP Project 10-64 has developed recommended uniform guidelines for inspection and condition evaluation of in-service FRP bridge decks and developed and implemented the pilot session of a course to train bridge inspectors on the methods of inspecting these bridge decks. The study is based on current state-of-the-art knowledge on FRP material and decks; ongoing research; experiences of bridge owners, maintainers, fabricators, and designers; knowledge from the defense and aerospace industries; and the state of current practice in the use and assessment of this material in the United States and in other countries. Information in support of this research was gathered primarily through two sources— published literature and the unpublished accounts and experiences of owners, inspectors, practicing engineers, researchers, and others associated with FRP material in general and FRP decks in particular. The collected information was used in conjunction with the experiences of the research team members to develop practical insights into the current state of inspection practice, inspection requirements, and inspection and assessment methods for FRP bridge decks. Based on the research, the key conclusions made by the research team are summarized below: • Due to the relatively young age of the FRP bridge deck inventory, the decks are currently in good condition in general. Many of these bridge decks have been instrumented and monitored, and most have undergone load tests at regular intervals for 2 or more years after construction. However, on some isolated bridge decks, problems have been observed, prompting extensive evaluation and remedial activities. • Awareness regarding the unique nature of FRP decks is lacking when compared with decks and components made of conventional construction materials. Therefore, the need for FRP-specific inspection requirements continues.

• In addition to the inspection manual, future development of analytical rating and maintenance guidelines for FRP decks and components is warranted. • The many commercial variants of FRP bridge deck types in service today make it more challenging to design, build and maintain FRP deck types. Because technical innovation and competitiveness will continue, new design and fabrication and construction methods will proliferate, perhaps causing some of the existing systems to become obsolete. Therefore, the research team urges that AASHTO, state highway departments, and the funding agencies maintain efforts like this one to create and communicate relevant guidelines and other information related to design, manufacture, construction, inspection, and maintenance of FRP bridge decks. • The research team has identified crucial performance details for each major type of FRP deck design. These details have been classified into two categories, one specific to the details within the deck sections and the other containing details associated with connections and other locations external to the deck cross section. The visual and tap-test methods are presently the most suitable techniques for inspection of FRP decks. Other advanced methods should be used to perform more-detailed investigations and structural evaluations after specific areas of interest are identified through visual or tap-test techniques. • The research team found that limited data were available for quantifying the severity and criticality of defects. Most of data and research in this area have been restricted to military and aerospace research with almost no systematic studies conducted for FRP bridge decks. The research team developed a semi- empirical scale for assessing the severity of defects and damage in FRP decks by using experiences from other industries. The research team compiled this knowledge base on inspection of FRP deck while performing Tasks 1 through 5 and used it to develop the inspection manual and training course. • In addition to those discussed above, the research team has discovered knowledge gaps in the state-of-the-art research. The research team feels that the variety of deck designs has contributed significantly to the creation of these knowledge gaps. Specific research is limited in the following areas and needs to be initiated: – Fatigue, durability, and the effect of environmental loads on FRP decks. – Damage initiation and propagation in FRP decks. This type of data is particularly important for assessing deck sections near curbs, railings, and other connection areas where there is high probability for impact and damage. – The post-damage behavior, remaining strength, and remaining life of FRP decks. Although such studies have been conducted in the defense and Field Inspection of In-Service FRP Bridge Decks: Report 156

157 Field Inspection of In-Service FRP Bridge Decks: Report aerospace industries, the studies have not yet been extended to civil engineering applications. – Composite action or the effect of composite action on FRP decks. Many FRP decks have been constructed with deck-to-stringer connection details that foster composite action and therefore should be studied to understand the effect of composite action on the FRP deck.

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159 Field Inspection of In-Service FRP Bridge Decks: Report of St. James, Phelps County, MO, Missouri DOT Report RDT02-012, Missouri DOT, 2002. 13. Zhou, A. “Stiffness and Strength of Fiber Reinforced Polymer Composite Bridge Deck Systems,” Dissertation for Ph.D. in Engineering Mechanics, Virginia Polytechnic Institute and State University, 2002. 14. Davalos, J.D., Barbero, E.J., and Qiao P. “Step-by-Step Engineering Design Equations for Fiber-Reinforced Plastic Beams on Transportation Structures,” West Virginia DOT, 1999. 15. U.S. Department of Defense. Composite Materials Handbook, Volume 1: Polymer Matrix Composites: Guidelines for Characterization of Structural Materials, Military Handbook MIL-HDBK-17-1F, Washington, DC, June 2002. 16. U.S. Department of Defense. Composite Materials Handbook, Volume 2: Polymer Matrix Composites: Material Properties, Military Handbook MIL- HDBK-17-2F, Washington, DC, June 2002. 17. U.S. Department of Defense. Composite Materials Handbook, Volume 3: Polymer Matrix Composites: Materials Usage, Design, and Analysis, Military Handbook MIL-HDBK-17-3F, Washington, DC, June 2002. 18. U.S. Department of Defense. Composite Materials Handbook, Volume 4: Metal Matrix Composites, Military Handbook MIL-HDBK-17-4A, Washington, DC, June 2002. 19. U.S. Department of Defense. Composite Materials Handbook, Volume 5: Ceramic Matrix Composites, Military Handbook MIL-HDBK-17-5, Washington, DC, June 2002. 20. U.S. Department of Defense. Nondestructive Active Testing Techniques for Structural Composites, Military Handbook MIL-HDBK-793(AR), Washington, DC, November 1989. 21. Scala, E.P. “A Brief History of Composites in the U.S.—The Dream and the Success.” JOM: The Member Journal of the Minerals, Metals & Materials Society, 48 (2), 1996, pp. 45–48. 22. Tang, B. “Fiber Reinforced Polymer Composites Applications in the U.S.,” Proceedings of the First Korea/U.S.A. Road Workshop, Federal Highway Administration, January, 1997. 23. Tang, B., and Podolny, Jr., W. “A Successful Beginning for Fiber Reinforced Polymer (FRP) Composite Materials in Bridge Applications.” Proceeding of FHWA International Conference on Corrosion and Rehabilitation of Reinforced Concrete Structures, Orlando, FL, December 1998.

24. Hooks, J., et al. FHWA Study Tour for Advanced Composites in Bridges in Europe and Japan. Federal Highway Administration, December 1997. 25. Kumar, P., Chandrashekhara, K., and Nanni, A. “Testing and Evaluation of Components for a Composite Bridge Deck,” Journal of Reinforced Plastics and Composites, 2001. 26. Chiewanichakorn, M., Aref, A., and Alampalli, S. “An Analytical Study of an FRP deck on a Truss Bridge,” State University of New York at Buffalo, 2001. 27. Alampalli, S., and Kunin, J. Load Testing of an FRP Bridge Deck on a Truss Bridge, REPORT FHWA/NY/SR-01/137, New York State DOT, 2001. 28. Alampalli, S., O’Connor, J., and Yannotti, A. P. Design, Fabrication, Construction, and Testing of an FRP Superstructure, REPORT FHWA/NY/SR- 00/134, New York State DOT, 2000. 29. Structures Design Advisory: Guidance for FRP Repair and Strengthening of Concrete Substructures,” advisory circular, New York State DOT, 2002. 30. U.S. Department of Defense. Glass Reinforced Plastics Preventive Maintenance and Repair. Military Handbook MIL-HDBK-803, Washington, DC, April 1990. 31. Federal Aviation Administration. Maintenance Inspection Notes for Boeing B- 707/720 Series Aircraft, FAA AC20-76, Washington, DC, October 1971. 32. Federal Aviation Administration. Composite Aircraft Structure, FAA AC20- 107A, Washington, DC, April 1984. 33. U.S. Army Corps of Engineers. Engineering and Design: Composite Materials for Civil Engineering Structures, ETL 1110-2-548, Washington, DC, March 1997. 34. “Project 129-99 Self-Help Guide for In-Service Inspection of FRP Equipment and Piping Communications,” Materials Technology Institute of Chemical Process Industry, Inc., 2001. 35. Johnson, D.B., Newhouse, N.L., Baldwin, D.D., and Lo, K.H. “Codes and Standards for Composite Tanks and Vessels: A General Discussion,” Third International Conference on Composite Materials for Offshore Operations, Houston, TX, 2000. 36. Navigation and Vessel Inspection Circular No. 0-97, NVIC 0-97, COMDTPUB P16700.4, U.S. Department of Defense, 1996. 37. Cowley, T. W. “Inspection of FRP Equipment: When and How to Inspect and What to Look For,” TAPPI 1991 Engineering Conference, Dow Chemical Company, 1991. Field Inspection of In-Service FRP Bridge Decks: Report 160

161 Field Inspection of In-Service FRP Bridge Decks: Report 38. Sadka, B. Performance Assessment of FRP Decks, research report, U.K. Highway Research Agency, 2002. 39. Ratcliffe, C.P. Crane, R.M., Gillespie, J.W., and Heider, D. “Bridge Evaluation Workshop: Field Load Testing and Long-Term Monitoring—New Technologies (SIDER),” Bridge Evaluation Workshop Presentation, U.S. Naval Academy, 2002. 40. Duke, J.C., Case, S., and Lesko, J.J., “NDE of FRP Decks and Beams,” Presentation at the 29th Annual Review of QNDE 2002, Virginia Polytechnic Institute and State University, 2002. 41. Miceli M., Pitkin, L., Horne, M.R., and Duke Jr., J.C. “Health Monitoring of FRP Bridge Decks,” Presentation at SPIE NDE For Health Monitoring, 2001. 42. Turner, M.K., Harries, K.A., and Petrou, M.F. “In-situ Structural Evaluation of GFRP Bridge Deck System,” Paper presented at the 82nd Annual Meeting of the Transportation Research Board, Washington, DC, 2003. 43. Dillenz, A., Busse, G., and Wu, D. Ultrasound Lockin Thermography: Feasibilities and Limitations, SPIE, 1999. 44. Lever, J.M., and Hamilton III, J.R. “Nondestructive Evaluation of Carbon Fiber- Reinforced Polymer-Concrete Bond Using Infrared Thermography,” ACI Materials Journal, 2003. 45. Lenett, M.S., Helmicki, A.J., and Hunt, V.J. “Multi-Reference Impact Testing of FRP Bridge Deck Material,” Proceedings of the 18th International Modal Analysis Conference, San Antonio, TX, 2000. 46. Dutta, P.K., Kwon, S., and Lopez-Anido, R. “Fatigue Performance Evaluation of FRP Composite Bridge Deck Prototypes Under High and Low Temperatures,” Paper presented at the 82nd Annual Meeting of the Transportation Research Board, Washington, DC, 2003. 47. Senne, J.L. “Fatigue Life of Hybrid FRP Composite Beams,” M.S. Thesis, Virginia Polytechnic Institute and State University, 2000. 48. Tang, H., Nguyen, T., Chuang, T., and Lesko, J. “Fatigue Model for Fiber- Reinforced Polymeric Composites in Civil Engineering Applications,” Virginia Polytechnic Institute and State University, 1997. 49. Kan, H.P. Enhanced Reliability Prediction Methodology for Impact Damaged Composite Structures, Report DOT/FAA/AR-97/79, Federal Aviation Administration, Washington DC, 1998.

50. McGowan, D.M., and Ambur, D.R. “Damage Characteristics and Residual Strength of Composite Sandwich Panels Impacted with and without a Compression Loading,” Paper presented the 39th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, American Institute of Aeronautics and Astronautics, 1998. 51. Nyman, T. Fatigue and Residual Strength of Composite Aircraft Structures, Report 99-26, Department of Aeronautics, Kungliga Tekniska Hogskolan (Royal Institute of Technology), SE-10044 Stockholm, Sweden, 1999. 52. Tomblin, J., Lacy, T., Smith, B., and Hooper, S. Review of Damage Tolerance for Composite Sandwich Airframe Structures, DOT/FAA/AR-99/49, Federal Aviation Administration, Washington DC, 1999. 53. Tomblin, J., and Raju, S. “Damage Tolerance of Composite Sandwich Airframe Structures,” Wichita State University, 2002. 54. Case, S., South, J., Duthoit, J., and Reifsnider, K. “Life Prediction Techniques for Composite Materials,” presentation at Virginia Polytechnic Institute and State University, 1999. 55. Case, S., and Reifsnider, K. “Simulation of Performance and Life Prediction for Composite Laminates: MRLife12,” Software Program Manual, Virginia Polytechnic Institute and State University, 1999. 56. Swartz, D., and Ilcewicz, L. “Fatigue and Damage Tolerance Perspectives for Composite Aircraft Structures,” Presented at the FAA/DOD/NASA Aging Aircraft Conference, 2002. 57. Sarkani, S., and Michaelov, G. “Nonlinear Damage Accumulation in Stochastic Fatigue of FRP Laminates,” Presented at the 8th ASCE Specialty Conference on Probabilistic Mechanics and Structural Reliability, ASCE, 2000. 58. Jolma, P. “Residual Strength of Laterally Loaded CFRP/PVC Sandwich Panels with Impact Damage,” Paper based on the Nordsandwich-project, Report BVAL36-011116, Technical Research Centre of Finland, Espoo, 2001. 59. Barbero, E. J., and De Vito, L. “A Constitutive Model for Elastic Damage in Fiber Reinforced PMC Laminate,” Research report, NSF Research Grant CMS-9612162, National Science Foundation, 2000. 60. Park, S.W., Veazie, D.R., and Zhou, M. Post-Impact Aging of FRP Composite Laminates in the Marine Environment, U.S. Department of Defense, Office of Naval Research, 2000. Field Inspection of In-Service FRP Bridge Decks: Report 162

163 Field Inspection of In-Service FRP Bridge Decks: Report APPENDIXES FOR REPORT The following appendixes are not published herein but are available online at trb.org/news/blurb_detail.asp?id=5905: • Appendix 1: List of Reviewed Literature • Appendix 2: Survey Questionnaire • Appendix 3: Survey Results • Appendix 4: Summary of Installed FRP Decks and Their Damage Inspection • Appendix 5: Connection Details and Critical Inspection Points • Appendix 6: Damage Types • Appendix 7: Inspection Methods • Appendix 8: Manual for Inspection of In-Service FRP Bridge Decks • Appendix 9: Assessment of Likelihood of Damage Progression • Appendix 10: Training Guide and Presentation for Manual for Inspection of In- Service FRP Bridge Decks