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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
 |
| Publication Number: FHWA-HRT-14-070 Date: September 2014 |
Publication Number: FHWA-HRT-14-070 Date: September 2014 |
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Cable-stayed bridges have become the form of choice over the past several decades for bridges in the medium-to-long-span range. 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 wind tunnel testing of a full-scale cable model to evaluate the influence of damping, turbulence, and aerodynamic surface treatment on cable stability. 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 the Guide Specification, 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 third in a series of reports addressing the subject of aerodynamic stability of bridge stay cables that will be published in the coming months.
Jorge E. Pagán-Ortiz
Director, Office of Infrastructure
Research and Development
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 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.
FHWA-HRT-14-070 |
2. Government Accession No. | 3 Recipient's Catalog No. | ||
| 4. Title and Subtitle
Wind Tunnel Investigations of an Inclined Stay Cable with a Helical Fillet |
5. Report Date September 2014 |
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| 6. Performing Organization Code | ||||
| 7. Author(s)
Guy L. Larose and Annick D’Auteuil |
8. Performing Organization Report No. LTR-AL-2011-0093 |
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9. Performing Organization Name and Address National Research Council of Canada
Genex Systems, LLC |
10. Work Unit No. (TRAIS) |
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| 11. Contract or Grant No.
DTFH61–07–D–00034 |
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| 12. Sponsoring Agency Name and Address
Office of Infrastructure R&D |
13. Type of Report and Period Covered
Laboratory Report |
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14. Sponsoring Agency Code HRDI-50 |
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| 15. Supplementary Notes
The Contracting Officer’s Technical Representative (COTR) was Harold R. Bosch, (HRDI-50). |
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| 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. 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 has 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 modifications to exterior cable surfaces effectively disrupts the formation of a water rivulet.
The objective of this study is to supplement the existing knowledge base on some of the outstanding issues of stay cable vibrations and to develop technical recommendations that may be incorporated into design guidelines. Specifically, this project focused on the wind-cable interaction, with particular interest in details of the air flow and flow field close to the cable as well as forces on the cable surface. A helical fillet was attached to an existing cable model to evaluate the influence of this common mitigation feature on dynamic behavior. The cable inclination angle was varied during testing to represent field orientations, and the model was rotated on its longitudinal axis to assess the influence of high-density polyethylene roundness. Tests were conducted at various levels of damping, with and without the fillet, and in turbulent as well as smooth flow conditions. |
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| 17. Key Words
Cable-stayed bridges, Cables, Vibrations, Wind, Rain, Wind tunnel testing, Wind turbulence, Galloping, Vortex shedding, Aerodynamic surface treatment, Helical fillet |
18. Distribution Statement
No restrictions. This document is available to the public through the National Technical Information Service, Springfield, VA 22161. |
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19. Security Classification Unclassified |
20. Security Classification Unclassified |
21. No. of Pages 222 |
22. Price | |
| Form DOT F 1700.7 (8-72) | Reproduction of completed page authorized |
SI* (Modern Metric) Conversion Factors
CHAPTER 2: EXPERIMENTAL CONDITIONS
CHAPTER 3: EXPERIMENTAL PROCEDURES AND ANALYSIS
CHAPTER 4: RESULTS AND DISCUSSION OF EXPERIMENTS
APPENDIX A. DETAILED LIST OF RUNS AND EXPERIMENTAL CONDITIONS
APPENDIX B. SUMMARY OF RESULTS
| Symbols | |
| Cd | Drag coefficient. |
| Cx | Along-wind force coefficient. |
| Cy | Across-wind force coefficient |
| d, D | Cable diameter. |
| f | Frequency. |
| I | Turbulence intensity. |
| L | Wind exposed length of cable model. |
| xL | Integral length scale of turbulence. |
| m | Mass per unit exposed length of cable model. |
| q | Dynamic pressure |
| Re | Reynolds number. |
| Sc | Scruton number. |
| U | Mean wind speed. |
| U/ f B | Reduced velocity. |
| ɑ | Spring rotation. |
| β | Flow yaw angle. |
| ζ | Damping ratio as a fraction of critical. |
| θ | Stay cable inclination. |
| μ | Air viscosity |
| ρ | Air density. |
| φ | Model inclination. |
| Subscripts | |
| h | Heave, along-wind. |
| s | Sway, across-wind. |
| u,v,w | Longitudinal, lateral, and vertical components of the flow fluctuations. |
