Primer for the Inspection and Strength Evaluation of Suspension Bridge Cables Publication No. FHWA-IF-11-045 May 2012 U.S. Department of Transportation Federal Highway Administration Notice This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for use of the information contained in this document. This report does not constitute a standard, specification, or regulation. Quality Assurance Statement The Federal Highway Administration provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. Primer for the Inspection and Strength Evaluation of Suspension Bridge Cables Publication No. FHWA-IF-11-045 May 2012 Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-IF-11-045 4. Title and Subtitle 5. Report Date Primer for the Inspection and Strength Evaluation of Suspension Bridge May 2012 Cables 6. Performing Organization Code 7. Author(s) 8. Performing Organization Report No. Brandon W. Chavel, Ph.D., P.E., and Brian J. Leshko, P.E. 9. Performing Organization Name and Address 10. Work Unit No. HDR Engineering, Inc. 11 Stanwix Street, Suite 800 11. Contract or Grant No. Pittsburgh, Pennsylvania 15222 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Office of Bridge Technology Technical Report Federal Highway Administration September 2007 – May 2012 1200 New Jersey Avenue, SE Washington, D.C. 20590 14. Sponsoring Agency Code 15. Supplementary Notes FHWA Contracting Officer’s Technical Representative (COTR): Raj Ailaney, P.E. FHWA Contracting Officer’s Task Manager: Myint Lwin, P.E., S.E. 16. Abstract This Primer is intended to be a practical supplement to NCHRP Report 534, Guidelines for Inspection and Strength Evaluation of Suspension Bridge Parallel Wire Cables, and FHWA Report No. FHWA-PD-96-001, titled Recording and Coding Guide for the Structure Inventory and Appraisal of the Nation’s Bridges. This Primer will serve as an initial resource for those involved in the inspection, metallurgical testing, and strength evaluation of suspension bridge cables in addition to providing necessary documentation for recording performed inspections, testing, and strength evaluations. Furthermore, this document is intended to provide field inspectors, technicians, and/or engineers with the necessary forms and information they need to perform an inspection. 17. Key Words 18. Distribution Statement Suspension Bridge, Bridge Cable, Inspection, Strength No restrictions. This document is available to the public through Evaluation, Bridge Cable Material Testing, NCHRP Report the National Technical Information Service, Springfield, VA 534 22161. 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of Pages 22. Price Unclassified Unclassified Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized Primer for the Inspection and Strength Evaluation of Suspension Bridge Cables Table of Contents FOREWORD .................................................................................................................................. 1 ACKNOWLEDGEMENTS ............................................................................................................ 2 1.0 Introduction ............................................................................................................................ 3 1.1 Documents ....................................................................................................................... 3 1.2 Primer Organization ......................................................................................................... 3 1.3 Suspension Bridge Cables................................................................................................ 4 1.3.1 Bridge Cable Components ...................................................................................... 5 1.3.2 Bridge Cable Protection .......................................................................................... 9 1.3.3 Causes of Cable Deterioration .............................................................................. 10 1.3.4 Cable Wire Corrosion ........................................................................................... 11 2.0 Inspection Guidelines and Laboratory Testing Methods ..................................................... 14 2.1 Cable Inspection............................................................................................................. 14 2.1.1 Levels of Inspection and Inspection Intervals ...................................................... 15 2.1.1.1 Inspections by Maintenance Personnel ............................................... 15 2.1.1.2 Biennial Inspections ............................................................................ 15 2.1.1.3 Internal Inspections ............................................................................. 21 2.1.2 Outline of Internal Inspections.............................................................................. 29 2.1.3 Outline of Inspection and Sampling ..................................................................... 30 2.1.4 Splicing of New Wires into the Cable .................................................................. 31 2.2 Cable Inspection............................................................................................................. 32 2.2.1 Tests of Wire Properties........................................................................................ 32 2.2.1.1 Specimen Preparation ......................................................................... 32 2.2.1.2 Tensile Tests ....................................................................................... 33 2.2.1.3 Obtaining Data for Stress vs. Strain Curves ....................................... 33 2.2.1.4 Fractographic Examination of Suspect Wires ..................................... 33 i 2.2.1.5 Examination of Fracture Surface for Pre-existing Cracks .................. 34 2.2.2 Zinc Coating Tests ................................................................................................ 34 2.2.2.1 Weight of Zinc Coating ...................................................................... 35 2.2.2.2 Preece Test for Uniformity ................................................................. 35 2.2.3 Chemical Analysis ................................................................................................ 35 2.2.4 Corrosion Analysis................................................................................................ 36 3.0 Evaluation of Field and Laboratory Data overview ............................................................. 37 3.1 Mapping and Estimating Wire Deterioration ................................................................. 37 3.1.1 Number of Rings in the Cable .............................................................................. 37 3.1.2 Number of Wires in Each Ring ............................................................................. 38 3.1.3 Wire Deterioration/Corrosion Mapping ................................................................ 38 3.1.4 Fraction of Cable in Each Corrosion Stage........................................................... 40 3.1.5 Number of Broken Wires ...................................................................................... 41 3.2 Wire Properties .............................................................................................................. 42 3.2.1 Cracked Wires as a Separate Group ...................................................................... 42 3.2.2 Individual Wire Properties .................................................................................... 43 3.2.2.1 Mean Properties .................................................................................. 43 3.2.2.2 Minimum Properties in a Panel Length .............................................. 44 3.2.3 Wire Group Mean Strength and Standard Deviation ............................................ 45 3.3 Wire Redevelopment ..................................................................................................... 45 4.0 Estimation of Cable Strength ............................................................................................... 46 4.1 Wire Groupings .............................................................................................................. 47 4.2 Strength of Unbroken Wires .......................................................................................... 47 4.2.1 Simplified Strength Model .................................................................................... 47 4.2.1.1 Mean Tensile Strength of Uncracked Wires ....................................... 48 4.2.1.2 Cable Strength Using the Simplified Model ....................................... 48 4.2.2 Brittle-Wire Strength Model ................................................................................. 49 4.2.3 Limited Ductility Strength Model ......................................................................... 50 4.3 Non-applicability of Load and Resistance