U.S. Department of Transportation
Federal Highway Administration
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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-14-066 Date: September 2014 |
Publication Number: FHWA-HRT-14-066 Date: September 2014 |
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Wind-induced vibration of ancillary structures that support signs and lights for traffic operations has been known to cause fatigue cracks that sometimes lead to collapse. Since approximately 1990, many researchers have called attention to this problem, and prior research has led to many changes in the American Association of State Highway Transportation Officials Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals. One particular detail of interest is the ring-to-tube connection used at the base of poles, commonly referred to as a socket connection. Typically, these connections have demonstrated comparatively reduced fatigue resistance. Much of the data on socket connection fatigue reveals that poles which had been galvanized have reduced fatigue strength. However, not all owners galvanize their structures, meaning the fatigue resistance of non-galvanized structures is being unnecessarily discounted. This project specifically addressed the difference in socket connection fatigue resistance between galvanized and ungalvanized poles. This report will assist stakeholders, including State transportation departments, researchers, consultants, and industry representatives, with the design and review of ancillary sign structures.
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.
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-14-066 |
2. Government Accession No. | 3 Recipient's Catalog No. | ||
| 4. Title and Subtitle
Fatigue Testing of Galvanized and Ungalvanized Socket Connections |
5. Report Date September 2014 |
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| 6. Performing Organization Code | ||||
| 7. Author(s)
Justin M. Ocel, Ph.D., P.E. |
8. Performing Organization Report No.
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9. Performing Organization Name and Address Federal Highway Administration |
10. Work Unit No. (TRAIS) |
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| 11. Contract or Grant No. | ||||
| 12. Sponsoring Agency Name and Address
Office of Infrastructure Research and Development |
13. Type of Report and Period Covered
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14. Sponsoring Agency Code HRDI-40 |
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| 15. Supplementary Notes | ||||
| 16. Abstract
The fatigue resistance of welded traffic signal support structure details is an ongoing research topic being addressed at multiple universities primarily through state funding mechanisms. Fatigue problems with these structures have plagued multiple states, and a handful of collapses are identified in the open literature. Some premature failures have been hypothesized to have been caused by cracking in the zinc metal bath during galvanizing. This led to a fatigue testing matrix of socket connection geometries in a galvanized and ungalvanized state. Specimens were attained from two different pole manufacturers and fabricated using their own techniques. This report describes how the specimens were tested along with the results showing the difference in fatigue life between galvanized and ungalvanized structures. Generally, the galvanized specimens showed a one-category reduction in fatigue life versus identical specimens that were not galvanized. |
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| 17. Key Words
Sign pole, fatigue, socket connection, galvanizing, wind vibration, tube-to-plate, ancillary structure |
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 43 |
22. Price N/A |
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| Form DOT F 1700.7 | Reproduction of completed page authorized |
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