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Publication Number:  FHWA-HRT-14-023    Date:  May 2014
Publication Number: FHWA-HRT-14-023
Date: May 2014


Corrosion Monitoring Research for City of New York Bridges

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Cable suspension bridges are essential components in the transportation networks of large metropolitan areas, such as the City of New York, and their serviceability is extremely important for economic and societal growth. The safety of such structures is closely linked to the safety performance of the cable supported system and, in particular, of their main cables. Currently, all State and local agencies base their maintenance plan mainly on previous experience and on limited visual inspection of the exterior and sometimes the interior of the cable. This report presents the results of a study aimed at developing a corrosion monitoring system for main cables of suspension bridges. Direct and indirect sensing technologies were reviewed, tested, and integrated in a redundant system that is able to monitor quantities like temperature, relative humidity, and corrosion rate. All these technologies were tested on a 20-ft (6.1-m)-long, 20-inch (508-mm)-diameter cable mockup before the field installation on two panels of one of the main cables of the Manhattan Bridge in New York, NY. The sensor system developed for this project recorded measurements of the temperature, relative humidity, and corrosion rate from inside the main cable for a period of almost 1 year, providing valuable information on the internal environment of an in-service main cable. This report will be of interest to highway managers; engineers involved in design, construction, and operations; and researchers.

Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development


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 the use of the information contained in this document. This report does not constitute a standard, specification, or regulation.

The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers' names appear in this report only because they are considered essential to the objective of the document.

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Technical Report Documentation Page

1. Report No.


2. Government Accession No. 3 Recipient's Catalog No.
4. Title and Subtitle

Corrosion Monitoring Research for City of New York Bridges

5. Report Date

May 2014

6. Performing Organization Code
7. Author(s)

Raimondo Betti, Dyab Khazem, Mark Carlos, Richard Gostautas, and
Y. Paul Virmani

8. Performing Organization Report No.


9. Performing Organization Name and Address

Columbia University
Department of Civil Engineering and Engineering Mechanics
500 W. 120th Street, New York, NY 10027


Parsons Transportation Group
100 Broadway, New York, NY 10005


Physical Acoustics Corporation
195 Clarksvill Road, Princeton Junction, NY 08550

10. Work Unit No. (TRAIS)

11. Contract or Grant No.
12. Sponsoring Agency Name and Address

Office of Infrastructure Research and Development
Federal Highway Administration
6300 Georgetown Pike
McLean, VA 22101-2296

13. Type of Report and Period Covered

Final Report

14. Sponsoring Agency Code


15. Supplementary Notes

The Contracting Officer's Technical Representative (COTR) was Y. Paul Virmani, HRDI-60.

16. Abstract

Current inspection procedures for suspension bridge main cables mainly consist of visually inspecting the exterior covering of the cable every 2 years. An indepth inspection is usually scheduled as necessary to assess the condition of the interior wires by wedging the cable at selected locations along the cable. However, such approaches were found to be deficient in uncovering the most deteriorated and weakest regions in the cables of several bridges during their full cable rehabilitation projects.


In this study, an integrated methodology was developed that uses state-of-the-art sensing capabilities and non-destructive evaluation (NDE) technologies to assess the cable condition. A smart sensor system integrated with NDE technologies is an approach that shows potential for assessing the condition of suspension bridge cables. NDE technologies for direct detection of the corrosion damage (i.e., main flux method, magnetostrictive technology, and acoustic emission technology) were implemented, validated, and tested for suspension bridge cable applications. In addition, a network of sensors that can monitor the external and internal environment of such cables and provide information that can be used to indirectly assess the cable's deterioration conditions and their evolution over time were assembled and extensively tested. In the selection of the sensors to be used for indirect sensing, special consideration was placed in considering the performance of such sensors in realistic service conditions such as a harsh environment, extreme reversals in cyclic histories (temperature, humidity, strain, electrochemical activity byproducts, etc.), large compaction forces, etc.


To recreate conditions as close as possible to real operating conditions, a cable mockup, which was 20 inches (508 mm) in diameter and 20 ft (6.1 m) long and subjected to 1,100 kips (4,893,043.76 N) and fully instrumented, was built at Columbia University and tested in an enclosed accelerated corrosion chamber. The results showed that the selected sensors were able to successfully measure temperature, humidity, and corrosion rate within the cable. The same system was then installed on two panels of the Manhattan Bridge, and measurements of temperature, relative humidity, and corrosion rate in the cable interior were successfully recorded for almost 1 year from November 2010 to September 2011.

17. Key Words

Main cables, Suspension bridges, Corrosion, Monitoring

18. Distribution Statement

No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161

19. Security Classification
(of this report)


20. Security Classification
(of this page)


21. No. of Pages


22. Price
Form DOT F 1700.7 Reproduction of completed page authorized


SI* (Modern Metric) Conversion Factors






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