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Publication Number:  FHWA-HRT-17-037    Date:  May 2018
Publication Number: FHWA-HRT-17-037
Date: May 2018


Dynamic Properties of Stay Cables on the Bill Emerson Bridge

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Cable-stayed bridges have become the design concept of choice over the past several decades for bridges in the medium- to long-span range. Nonetheless, in some cases, serviceability problems involving large-amplitude vibrations of stay cables under certain wind and wind/rain conditions have been observed. This study was conducted in response to State transportation departments’ requests to develop improved design guidance for mitigation of excessive cable vibrations on cable-stayed bridges. The study included full-scale forced vibration tests on the cables of a new cable-stayed bridge to characterize cable dynamic behavior and evaluate effectiveness of mitigation details such as crossties. The results of this study will be made available to the Post-Tensioning Institute’s DC-45 Cable-Stayed Bridge Committee for consideration during their periodic updates of its publication, Recommendations for Stay Cable Design, Testing and Installation.(1)

This report will be of interest to bridge engineers, wind engineers, and consultants involved in the design of cable-stayed bridges. It is the fifth in a series of reports addressing the subject of aerodynamic stability of bridge stay cables.(25)

Cheryl Allen Richter, Ph.D., P.E.
Director, Office of Infrastructure
Research and Development


This document is disseminated under the sponsorship of the U.S. Department of Transportation (USDOT) in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document.

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

Dynamic Properties of Stay Cables on the Bill Emerson Bridge

5. Report Date

May 2018

6. Performing Organization Code


7. Author(s)

Harold R. Bosch and James R. Pagenkopf

8. Performing Organization Report No.


9. Performing Organization Name and Address

Genex Systems, LLC
11848 Rock Landing Drive, Suite 303
Newport News, VA 23606

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

Laboratory Report; September 2002–September 2014

14. Sponsoring Agency Code


15. Supplementary Notes

The Contracting Officer’s Representative was Harold R. Bosch (HRDI-40).

16. Abstract

Cable-stayed bridges have been recognized as the most efficient and cost-effective structural form for medium- to long- span bridges over the past several decades. With their widespread use, cases of serviceability problems associated with large amplitude vibration of stay cables have been reported.(2) Stay cables are laterally flexible structural members with very low inherent damping and thus are highly susceptible to environmental conditions such as wind and rain/wind combination.


Recognition of these problems led to the incorporation of different types of mitigation measures on many cable-stayed bridges around the world. These measures include surface modifications, cable crossties, and external dampers. Modification of cable surfaces has been widely accepted as a means to mitigate rain/wind vibrations. Recent studies have firmly established the formation of a water rivulet along the upper side of the stay and its interaction with wind flow as the main cause of rain/wind vibrations. Appropriate modification of exterior cable surface effectively disrupts the formation of a water rivulet.(6–9)


The objective of this study was to supplement the existing knowledge base on some of the outstanding issues of stay cable vibrations and develop technical recommendations that may be incorporated into design guidelines. Specifically, this project focused on identifying in-situ cable dynamic properties and performance of crossties on the Bill Emerson Bridge near Cape Girardeau, MO. Forced vibration tests were conducted on the stay cables during the latter stages of construction just prior to and following installation of grout as well as before and after installation of a single line of crossties. Cable properties, such as vibration frequencies and damping levels, were established and compared with design targets. The measured cable frequencies compared well with values calculated using standard formulas and numerical methods. The measured levels of inherent damping in the cables were low as expected, and the resulting low Scruton numbers confirmed the need for installation of cable crossties.

17. Key Words

Cable-stayed bridges, Cables, Vibrations, Wind, Rain, Crossties, Hazard mitigation

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 (8-72) Reproduction of completed page authorized




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