94097058 FHWA Visual Bridge Inspection

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Reliability of Visual Inspection for Highway Bridges, Volume I: Final Report FHWA-RD-01-020 JUNE 2001 Research, Development, and Technology Turner-Fairbank Highway Research Center 6300 Georgetown Pike McLean, VA 22101-2296 FOREWORD Since the implementation of the National Bridge Inspection Program in 1971, State Departments of Transportation have invested significant resources to evaluate the condition of their bridges. These inspections are primarily conducted within the context of the Natio
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  Reliability of Visual Inspection forHighway Bridges,Volume I: Final Report FHWA-RD-01-020JUNE 2001 Research, Development, and TechnologyTurner-Fairbank Highway Research Center6300 Georgetown PikeMcLean, VA 22101-2296  FOREWORD Since the implementation of the National Bridge Inspection Program in 1971, StateDepartments of Transportation have invested significant resources to evaluate thecondition of their bridges. These inspections are primarily conducted within the contextof the National Bridge Inspection Standards that require reporting of bridge condition in astandardized format. This standardized format uses a uniform set of condition ratings todescribe the condition of a bridge. Key elements of the inspection include the conditionratings for the deck, superstructure, and substructure of the bridge. The assignment of condition ratings to elements of the bridge is used to measure bridge performance at thenational level, to forecast future funding needs, to determine the distribution of fundsbetween States, and to evaluate if a particular bridge renovation project qualifies forFederal assistance. Obviously, the accuracy of the condition ratings is important toensure that FHWA programs for funding bridge construction and renovation are equitableand meet the goal of reducing the number of deficient bridges.The accuracy and reliability of the inspection process that results in condition ratings forHighway Bridges has not been researched previously. This report documents thefindings of the first comprehensive study of the inspection process since the adoption of the National Bridge Inspection Standards. The study provides overall measures of thereliability and accuracy of bridge inspection, identifies factors that may influence theinspection results, and determines what procedural differences exist between variousState inspection programs. This report will be of interest to bridge engineers, designers,and inspectors who are involved with the inspection of our Nation’s highway bridges.T. Paul Teng, P.E.Director, Office of InfrastructureResearch and Development NOTICE This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Governmentassumes no liability for its contents or use thereof. This report does not constitute astandard, specification, or regulation.The United States Government does not endorse products or manufacturers. Trade andmanufacturers’ names appear in this report only because they are considered essential tothe object of the document.    Technical Report Documentation Page 1. Report No. FHWA-RD-01-020 2. Government Accession No. 3. Recipient’s Catalog No.5. Report Date4. Title and Subtitle RELIABILITY OF VISUAL INSPECTION FOR HIGHWAY BRIDGESVolume I: Final Report   6. Performing Organization Code7. Author(s) Mark Moore, PE; Brent Phares, Ph.D.; Benjamin Graybeal; Dennis Rolander;Glenn Washer, PE 8. Performing Organization Report No.10. Work Unit No. (TRAIS)11. Contract or Grant No. DTFH61-96-C-00054 9. Performing Organization Name and Address Wiss, Janney, Elstner Associates, Inc.225 Peachtree Street, NE, Suite 1600Atlanta, GA 30303   13. Type of Report and Period Covered Final ReportOctober 1998  – September 2000   12. Sponsoring Agency Name and Address NDE Validation CenterOffice of Infrastructure Research and DevelopmentFederal Highway Administration6300 Georgetown PikeMcLean, VA 22101-2296   14. Sponsoring Agency Code15. Supplementary Notes FHWA Contracting Officer’s Technical Representative (COTR): Glenn Washer, PE, HRDI-10 16. Abstract Visual Inspection is the predominant nondestructive evaluation technique used in bridge inspections. However, sinceimplementation of the National Bridge Inspection Standards in 1971, a comprehensive study of the reliability of Visual Inspectionas it relates to highway bridge inspections has not been conducted. The goals of the study include: providing overall measuresof the accuracy and reliability of Routine and In-Depth Visual Inspections, studying the influence of several key factors that affectRoutine and In-Depth Inspections, and studying the differences between State inspection procedures and reports.Ten inspection tasks were performed at seven test bridges using State bridge inspectors. The sample of participatinginspectors included 49 inspectors from 25 State agencies. Inspectors were provided with common information, instruction, andtools. Inspector characteristics were measured through self-report questionnaires, interviews, and direct measurements.Routine Inspections were completed with significant variability, and the Condition Ratings assigned varied over a range ofup to five different ratings. It is predicted that only 68 percent of the Condition Ratings will vary within one rating point of theaverage, and 95 percent will vary within two points. Factors that appeared to correlate with Routine Inspection results includeFear of Traffic; Visual Acuity and Color Vision; Light Intensity; Inspector Rushed Level; and perceptions of Maintenance,Complexity, and Accessibility.In-Depth Inspections using Visual Inspection alone are not likely to detect or identify the specific types of defects for whichthe inspection is prescribed, and may not reveal deficiencies beyond those that could be noted during a Routine Inspection. Theoverall thoroughness with which inspectors completed one of the In-Depth tasks tended to have an impact on the likelihood ofan inspector detecting weld crack indications. Other factors that may be related to In-Depth Inspection accuracy include: timeto complete inspection, comfort with access equipment and heights, structure complexity and accessibility, viewing of welds,flashlight use, and number of annual inspections performed.The State procedural and reporting tasks indicated that most States follow similar procedural and reporting criteria.Several inconsistencies were noted with the use of the element-level inspection systems, but it is not known if these variationsare the result of State practices or inspector use. Deck delamination surveys were found to have significant variability, with onlya few teams performing a delamination survey as part of the Routine Inspection.This volume is the first in a series of two. The other volume in the series is: FHWA-RD-01-021, Volume II: Appendices 17. Key Words Bridges, Routine Inspection, In-Depth Inspection,Delamination Survey, NBIS, Condition Ratings. 18. Distribution Statement No restrictions. This document is available to the publicthrough the National Technical Information Service, Springfield,VA 22161. 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 21. No. of Pages 516 22. Price Form DOT F 1700.7 (8-72) Reproduction of completed page authorized      iii TABLE OF CONTENTSPage1. INTRODUCTION ...................................................................................................................1 1.1. BACKGROUND ............................................................................................................1 1.2. OBJECTIVES ................................................................................................................1 1.3. SUMMARY OF APPROACH ......................................................................................4 2. LITERATURE   REVIEW .......................................................................................................7 2.1. VISUAL INSPECTION OF HIGHWAY STRUCTURES .........................................7 2.2. VISUAL INSPECTION IN OTHER INDUSTRIES ................................................12 2.3. FACTORS AFFECTING VISUAL INSPECTION ..................................................16 2.3.1. Physical Factors ...................................................................................................18 2.3.2. Environmental Factors .......................................................................................23 2.3.3. Management Factors ...........................................................................................26 2.4. SELECTION AND TRAINING OF VISUAL INSPECTORS ................................27 3. SURVEY   OF   STATES ..........................................................................................................31 3.1. SURVEY PARTICIPATION ......................................................................................31 3.2. SURVEY DESCRIPTION ...........................................................................................32 3.3. SURVEY RESULTS ....................................................................................................32 3.3.1. Section 1 – Composition of Bridge Inspection Team for VisualInspection .............................................................................................................33 3.3.2. Section 2 – Impact of Administrative Requirements on VisualInspection .............................................................................................................41  3.3.3. Section 3 – Current and Future Use of NDE Techniques ................................50 4. EXPERIMENTAL PROGRAM ..........................................................................................61 4.1. STUDY OVERVIEW ...................................................................................................61 4.2. STUDY PARTICIPANTS ...........................................................................................61 4.3. INSPECTION SPECIMENS .......................................................................................62 4.3.1. Bridge B521 ..........................................................................................................63 4.3.2. Bridge B101A .......................................................................................................65 4.3.3. Bridge B111A .......................................................................................................67 4.3.4. Bridge B543 ..........................................................................................................67
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