Structural Health Monitoring of Weathering Steel Overhead Sign Support Structures in West Virginia

Weathering steel (WS) is a high-strength, low-alloy steel that has been proven to provide a significantly higher corrosion resistance than non-weathering carbon steel. It is best known under the trademark COR-TEN or Corten steel. Although the initial material cost of WS is more expensive than that of traditional steels, it eliminates the need for painting, leading to reduced maintenance cost. In addition to its cost-effectiveness, WS provides some environmental benefits since no painting is required, no volatile organic compounds are released during maintenance painting, nor does disposal and containment of paint pose a concern. In the United States, WS has been used in highway bridges since the 1960s. Reports revealed that WS bridges performed well in most cases, but in the 1980s, some states began to experience less-than-desirable performance of their WS bridges. The use of de-icing salts on roadways and aggressive climate conditions (e.g. coastal and high-humidity environments, heavy rainfall and fog, etc.) are believed to be two major contributors to the corrosion of WS bridges. In West Virginia, there are approximately 100 WS bridges and numerous WS overhead sign structures (WSOSSs) throughout the state. Inspection of these WS structures is essential to maintain public safety. This paper aims at evaluating 11 WSOSSs in Charleston Interstate System in West Virginia (the full inventory includes 82 WSOSSs). A comprehensive inspection form was developed to objectively assess the current condition of single-armed ground mount cantilever WSOSSs. A reliable ultrasonic testing technique was used to examine critical components of the sign structures (e.g. anchor bolts, base plates, vertical columns near the column bases, connections between base plates and vertical columns, horizontal chords/vertical columns connections, etc.) while the other components were inspected by visual inspection technique. A rating methodology was developed to evaluate the sign structures at both the element-level and their overall condition. The element condition was rated based on the developed rating criteria and score. The overall condition of each sign structure was then evaluated by the ratio between the total score of each structure (S) and its maximum possible total score (Smax). As a result of this work, it is concluded that most of the WSOSSs performed relatively well after more than 40 years of service and exposure to moist weather condition of Kanawha County (climate zone 4A) in West Virginia. Specifically, as a result of the developed rating methodology, 45 percent of sign structures were found to be in fair condition, and 55 percent were in good condition. The rating system is intended to assist the WVDOT in making rational decisions about whether there is a need to repair or replace at-risk elements, connections, or structures.

References

 1. Zatar, Wael, Hai Nguyen, Ted Whitmore, and Ray Lewis, "An Inspection Framework for Assessing Condition of Ground Mount Truss/Cantilever Overhead Sign Structures," Proceedings of the Transportation Research Board (TRB) 94th Annual Meeting,  No. 15-2824, Washington, D.C., 2015.

2. Zatar, Wael and Hai Nguyen, “ Evaluation of Weathering Steel Overhead Sign Structures in West Virginia,” Research Report (317 pages) , West Virginia Department of Transportation, Division of Highways, Charleston, West Virginia, October 2014.

3. Zatar, Wael, Ted Whitmore, Ray Lewis, and Hai Nguyen, “ Evaluation of Weathering Steel Sign Structures in West Virginia,” Proceedings of the 1st National Conference on Intermodal Transportation: Problems, Practices, and Policy , Hampton, Virginia, October 11-12, 2012.

4. Garlich, S. E., and Eric T. Thorkildsen, Guidelines for the Installation, Inspection, Maintenance and Repair of Structural Supports for Highway Signs, Luminaires, and Traffic Signals,  No. FHWA NHI 05-036, 2005.

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