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57 APPENDIX B Survey Questionnaire QUESTIONNAIRE NCHRP SYNTHESIS TOPIC 35-08 INSPECTION AND MANAGEMENT OF BRIDGES WITH FRACTURE CRITICAL MEMBERS Please complete and return this questionnaire by March 19, 2004 Name: Title: Agency: Address: City: State: Zip: Phone: Fax: E-mail: Please return the completed questionnaire to: Robert J. Connor Lehigh University 117 ATLSS Drive Bethlehem, PA 18015 Phone: (610) 758-6103 Fax: (610) 758-5553 Email: rjc3@lehigh.edu We would greatly appreciate discussing any matters related to this survey with you on the telephone. If you have any ques- tions, comments, or can provide any additional information that is not identified in the questionnaire, please do not hesitate to call myself at 610-758-6103 or Robert J. Dexter at 612-624-0063. Background During the past three decades, special emphasis has been placed on the evaluation, inspection, and rehabilitation of bridges containing fracture-critical members (FCMs). FCMs are steel members in tension or with tension elements whose failure would probably cause a portion of or the entire bridge to catastrophically collapse. Bridges containing FCMs are commonly referred to as fracture-critical bridges (FCBs). This survey is being conducted as part of NCHRP Synthesis Topic 35-08: Inspection and Management of Bridges with Fracture Critical Members. One of the objectives of this survey is to gather information on fracture-critical structures and how bridge owners define, identify, inspect, and manage FCBs. Notes for Completing this Survey A copy of this survey should be given to all departments within your agency that have significant experience with FCBs (e.g., designers, inspectors, district bridge engineers). Multiple responses from a single agency are welcomed and encouraged.

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58 It would be advantageous to provide a copy to the individuals within the agency with the most experience and familiarity with the history of the bridge inspection and maintenance program of the agency. In responding to all of the questions below, if you do not have exact information or if it would be very difficult to obtain, please feel free to estimate the approximate answer and indicate that it is an estimate. It is better to have an estimate than no information at all. Also, please provide sketches, drawings, photographs, inspection reports and any other useful information if available. If you have such material in digital format, please send it via e-mail if possible. If this additional information is not digital in format, you can send this to us by regular mail. If you request, we will return it to you right away. QUESTIONNAIRE PART I--GENERAL 1. How does your agency define a fracture-critical bridge? Nearly all agencies responded that they either use the AASHTO or NBIS definitions. 2. Are different criteria used for different structural systems (e.g., are trusses identified using different criteria than box girders)? 33 No 7 Yes If yes, please describe the criteria: Results indicated the criteria are developed for specific projects on case-by-case basis. Some rely on a rank- ing system to prioritize inspection procedures based on age, average daily traffic, type of material, and type of fatigue details on the bridge. 3. How would you categorize the following bridges (place an `X' in the box to select the type of bridge)? Fracture Critical CHAPTER 10. Description Yes No Two girder bridges 38 0 Three girder bridges 9 28 Three girder bridges with girder spacing > ______ ft 10 21 Multi-girder bridges with girder spacing >_______ft 3 32 Truss bridges 34 3 Two girder bridges fabricated using HPS 70W 31 1 Truss bridges fabricated using HPS 70W steel 28 2 Single steel "tub" girder bridges 32 5 Twin steel "tub" girder bridges 22 12 Multi-steel "tub" girder bridges 0 34 Other (post-tensioned, timber, steel cross girders, etc.) 13 3 Are these answers your opinion or your agency's written policy? Engineering judgment in conjunction with established policies; e.g., NBIS and AASHTO. 4. Does your agency identify suspension bridges as fracture critical? 8 No 25 Yes

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59 If yes, what elements are considered fracture critical? _______________________________________________________________________ _______________________________________________________________________ 5. Does your agency currently have any fracture-critical bridges in its inventory? 1 No 39 Yes If you answered "yes" to question 5, please continue and complete the survey. If you answered "no," please return the survey to the address listed above. We thank you for your time. (ID = insufficient data.) PART II--INSPECTION AND CLASSIFICATION 1. How many steel bridges are in your inventory? 85,723 a. How many are fracture critical? 11.8% How many fracture-critical bridges were built before 1975? 76% How many fracture-critical bridges were built before 1985? 70% (ID) b. How many are non-fracture critical? 80% How many non-fracture-critical bridges were built before 1975? 67% How many non-fracture-critical bridges were built before 1985? 81% 2. Please provide a breakdown of the approximate number of each type of structure identified as fracture critical in your inventory. Some common types of bridges often identified as fracture critical are listed below: 16.4% Welded two-girder system (with bolted or welded field splices) 1.0% Welded three-girder system (with bolted or welded field splices) <1% Other welded girder systems considered fracture critical 8.6% Riveted two-girder system <1% Riveted three-girder system <1% Other riveted girder systems considered fracture critical 30.9% Riveted truss bridges with two truss lines 3.8% Welded truss bridges with two truss lines (with bolted or welded field splices) 1.6% Welded and bolted truss bridges with two truss lines 28% Bridges with steel pier caps 1.5% Bridges with pin and hanger systems 6.1% Bridges with steel cross girders <1% Bridges with single steel tub girders <1% Bridges with twin steel tub girders 1.1% Bridges with multi-steel tub girders 7.5% Other steel bridges considered fracture critical Please describe: Steel cross girders, cable supported, tied arch. 3.1% Other non-steel bridges (e.g., wood or post-tensioned concrete) considered fracture critical. Please describe: _______________________________________________________________________________________ _______________________________________________________________________________________ 3. Does your agency require any special inspection procedures for fracture-critical bridges? 11 No 29 Yes

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60 If yes, please describe below: Examples given: hands-on, arms length at defined intervals. 4. Does your agency require any special training or qualifications for individuals inspecting fracture-critical bridges? 17 No 23 Yes If yes, please describe below: Examples given: NHI, in-house training, FCB inspection team lead must have experience and in most cases be a PE. 5. What is the maximum interval (in years) between inspections of typical non-fracture-critical bridges permitted by your agency? Two years typically, 5 years maximum for in-depth. 6. What is the maximum interval (in years) between inspections of typical fracture-critical bridges permitted by your agency? Two years typically, 5 years maximum for in-depth. 7. Are there any special methods or nondestructive testing techniques required by your agency to inspect fracture-critical bridges? 25 Yes If yes, please briefly describe: Dye penetrant, UT, magnetic particle testing. 15 No The next two questions make a distinction between cursory inspection and detailed "hands-on" inspection. Your agency may not make such a distinction, so the answers would be the same. 8. What is the maximum interval (in years) between detailed "hands-on" inspections of typical non-fracture-critical bridge permitted by your agency? 5 9. What is the maximum interval (in years) between detailed "hands-on" inspections of typical fracture-critical bridge permitted by your agency? 5 10. If fracture-critical bridges are inspected at a greater frequency than non-fracture-critical bridges, is the entire bridge inspected more frequently or just the fracture-critical members? Most agencies answered no to this question and that interval is based on a case-by-case basis. Some agen- cies indicated that they only inspected the FCM, while others indicated the entire bridge is inspected since crews and equipment are on site. 11. Is there any significant increase in the costs associated with the inspection of fracture-critical bridges? 13 No 26 Yes

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61 If you answered "yes" to question 11, what are the reasons for the increased costs (e.g., increased frequency of inspec- tion, increased cost per inspection)? Traffic control, additional time on site to perform in-depth inspection, added equipment costs such as snooper, testing equipment, special FCB inspection team, etc. Can you attempt to estimate at the absolute or percentage increase in cost? (e.g., 10%, 15%, . . . etc.) Increase in cost due to frequency of inspection __________ Increase in cost per inspection __________ Other factors (please describe): _________________________________________________________________ ________________________________________________________________________________________________ 12. Is there any special or advanced analysis performed to identify which specific members are fracture critical or if the struc- ture is actually fracture critical (e.g., 3-D structural analysis, etc.)? 32 No 8 Yes If yes, please describe below: Some owners indicated that 3-D modeling has been conducted on a case-by-case basis, but none had a defined policy. 13. Has the inspection of a fracture-critical bridge(s) ever identified a condition that has clearly prevented a fracture and the subsequent collapse of the structure? (The objective of this question is to identify specific cases or examples whereby the additional inspection efforts dedicated to FCBs prevented a failure that would have occurred had the inspection not been carried out. For example, the discovery of typical out-of-plane distortion cracks, which usually take years to become crit- ical, would not warrant a response of "yes" for this question. Furthermore, inspections which found fractured members would also not warrant a response of "yes" for this question since the inspection did not prevent the fracture and the bridge did not fail.) 27 No 8 Yes 14. If you answered "yes" to question 13, please describe the problem(s) in detail. Bridge name and/or inventory number, location, year built: Questions 13 and 14 did not provide information intended. Question 13 was not worded clearly enough to deter- mine if inspection program found immediate problems. Only a few owners replied to both questions. Overall, most who replied felt inspection permitted them to find and correct a problem before failure occurred. 15. If a bridge normally identified as fracture critical had all fracture-critical members fabricated from HPS 70W steel, would there be any changes to the inspection methods or interval that you would recommend? Nearly all owners answered "no" to this question. However, the reason given for a response of "no" was almost always because FHWA/NBIS does not allow a change in inspection requirements if HPS 70W is used. 16. If a bridge normally identified as fracture critical was fabricated so that the worst fatigue category used was Category C would there be any changes to the inspection methods or interval that you would recommend? (Most multi-beam bridges built in the last twenty years do not have details worse than Category C.) Nearly all owners answered no to this question. 17. It is commonly observed that by using simplified structural analysis methods the calculations for many bridges indicate no remaining fatigue life or even "negative" fatigue life. These calculations imply that fatigue cracking should be observed presently or in the near future on these bridges. However, such bridges typically show no signs of fatigue-related prob-

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62 lems. (Please note this does not include cracking from secondary stresses, such as web gap cracking, as this type of crack- ing is not explicitly considered in fatigue rating calculations.) What is your agency's policy regarding cases when this inconsistency occurs? One state relied on a fracture mechanics approach to evaluate potential for fracture. Interestingly, many states do not check fatigue life on FCBs. Others, if they check fatigue, will retrofit the bridge or post the bridge. Over- all, none of the agencies that replied indicated a defined procedure to address this issue. 18. Are more rigorous methods ever used such as: a. Weigh-in-motion studies to better characterize loading Yes 4 If yes, how many bridges per year _____. No 36 b. Advanced analysis, such as grid or 3-D frame analysis Yes 13 If yes, how many bridges per year _____. No 27 c. Field instrumentation and/or controlled load testing or monitoring Yes 18 If yes, how many bridges per year _____. No 22 Please describe other methods and provide procedures as necessary. ________________________________________________________________________________________________ ________________________________________________________________________________________________ 19. What criteria are used to identify bridges that will be evaluated using the more rigorous methods for a fatigue evaluation? Owners indicated that these additional efforts are undertaken on a case-by-case basis. Influencing factors are structure size, age, average daily traffic, type of fatigue details on the bridge, overall condition (including fatigue problems) of the bridge. 20. In performing a fatigue evaluation, does your agency use a specific procedure for fracture-critical bridges? 9 Yes 30 No 21. If you answered "yes" to question 19, what is your level of confidence in these procedures? ____ Low ____ Medium ____ High Very few agencies answered this question. Those who replied indicated low-to-medium confidence.

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63 PART III--FAILURES The failures of interest in this section are only related to fractures. Cracking associated with fatigue that did not result in frac- ture should not be included in this group. However, fractures that have occurred as a result of a fatigue crack should be included. For all failures cited, please provide a description of the bridge, failure, inventory number of the bridge, and any other information you can provide. (ID = insufficient data.) 1. Has your agency ever experienced the failure of any non-fracture-critical bridges the cause of which could be attributed to any reason, such as fracture of a member, scour, vehicle impact, . . . etc? 8 No 31 Yes 2. If you answered "yes" to question 1, were there any fatalities? (Please provide information for each failure.) 20 No 13 Yes If yes, how many? ID 3. Has your agency ever experienced the failure of any fracture-critical bridges the cause of which was attributed to rea- sons other than fatigue or fracture of a member, such as, scour, impact, . . . etc? 24 No 16 Yes If yes, how many were prior to the implementation of the fracture-critical bridge inspection program (1975 for most agencies)? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ If yes, how many were after the implementation of the fracture-critical bridge inspection program? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ 4. If you answered "yes" to question 3, were there any fatalities? (Please provide information for each failure.) 11 No 2 Yes If yes, how many? ID 5. Has your agency ever experienced the failure of any fracture-critical bridges the cause of which was clearly attributed to fatigue or fracture of a member? 35 No 4 Yes If yes, how many? ID If yes, how many were prior to the implementation of the fracture-critical bridge inspection program (1975 for most agencies)? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________

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64 If yes, how many were after the implementation of the fracture-critical bridge inspection program? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ If you answered yes to question 5 were there any fatalities? ID No ID Yes If yes, how many? ______________ (Please provide information for each failure.) 6. Has your agency ever experienced a brittle fracture in a member of a fracture-critical bridge in which the bridge did not collapse catastrophically but remained standing? (For example, a girder may have fractured with damage only resulting in significant deflections or local buckling of other members.) 29 No 10 Yes If yes, how many? ________ID_______ If yes, how many were prior to the implementation of the fracture-critical bridge inspection program (1975 for most agencies)? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ If yes, how many were after the implementation of the fracture-critical bridge inspection program? ID Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ 7. Have existing small fatigue cracks ever been observed to propagate significantly (greater than 6 inches) between regu- larly scheduled inspections? 29 No 11 Yes If yes, how many were prior to the implementation of the fracture-critical bridge inspection program (1975 for most agencies)? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ If yes, how many were after the implementation of the fracture-critical bridge inspection program? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ 8. Have fatigue cracks ever resulted in fracture of a fracture-critical member? 34 No 4 Yes If yes, how many were prior to the implementation of the fracture-critical bridge inspection program (1975 for most agencies)? ________ID_______ Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________

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65 If yes, how many were after the implementation of the fracture-critical bridge inspection program? ID Bridge name and/or inventory number, location: _________________________________________________________ ________________________________________________________________________________________________ 9. If you answered "yes" to question 8, were tests conducted to determine the material properties of the steel? 1 No 5 Yes 10. If you answered "yes" to question 8, has it been confirmed through a detailed investigation that the fractures were initi- ated by the fatigue crack? 1 No 4 Yes 11. What was determined to be the specific cause of the fracture? There were very few responses to this question. Where additional information was given, fatigue, impact from ships, or constraint-induced fracture originating at intersecting weld (Hoan-like failure) were identified as the causes. 12. How long (in inches) was the fatigue crack at the time of fracture? (Please attach sketches, photographs, etc., as required.) ID 13. Would you be willing to speak with us over the telephone to discuss these failure(s) further? 6 No 15 Yes PART IV--RETROFIT PROCEDURES 1. Has your state or agency developed any policies for retrofit of bridges identified as fracture critical to improve redundancy? 30 No 7 Yes 2. Please provide copies of these policies. (Please attach documents as required.) ID 3. Have the retrofits been implemented or been scheduled to be implemented in the field on any bridges to date? 13 No 15 Yes 4. Can your agency identify any research needs related to fracture-critical steel bridges? 6 No. 6 Yes--if yes, please describe below. Some examples are provided below that can simply be checked. 8 Develop guidelines related to advanced structural analysis procedures to better predict service load behavior in fracture-critical bridges. 9 Develop advanced fatigue-life calculation procedures taking into account lack of visible cracks for fracture- critical bridges. 10 Field monitoring for fracture-critical bridges. 3 Crack arrest capabilities of bridge steel.

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66 7 Establish evaluation procedures for advanced large deformation and member death. 10 Develop advanced analyses techniques and procedures to investigate alternate load paths, redundancy, and bridge collapse. 1 Retrofit procedures to add redundancy. Others you may wish to suggest: ID--See responses to question 5 of this section. 5. Can your agency suggest any changes in the current practice of identifying, inspecting, or retrofitting fracture-critical steel bridges? _____ No _____ Yes If yes, please describe below. Develop methods to establish inspection intervals and criteria based on ADT/ADTT, age, detail types, exist- ing condition, etc. Develop fracture-critical inspection procedures for high-mast lighting towers, overhead sign bridges. These structures should be considered as fracture critical according to one respondent. The individual indicated that these structures are more problematic than their fracture critical bridges. Survey Completed--Thank You for Your Time