Effects of Traffic and Wind Loads on a Tied-Arch Bridge

摘要

The purpose of this study is to assess the sensitivity of four highway bridges towind and live loadings. The bridges are planned for construction on U.S. 59 in Houston, Texas. Each bridge will be of the tied-arch type and will be constructed on-grade over cut areas with clear spans in excess of 61 meters (200 feet). To expedite construction, unique procedures are planned which use existing bridges as platforms for final fabrication of the tied arches. This procedure requires consideration of wind loading on the arches during construction. In this study, the bridge design is analyzed under the expected wind loadings based on assumed aerodynamic parameters and the bridge details furnished by the Texas Department of Transportation. A geometrically-scaled wind tunnel model of a typical bridge was built and tested to determine the actual aerodynamic parameters. The wind tunnel test results and the traffic loading results are presented. The analytical study shows that the completed bridge is aerodynamically stable and will not have any major problems due to dynamic vibrations. The same is true for the partially constructed state where the two arches are braced together without the deck. Vortex shedding excitation emerged as more critical than buffeting excitation of the deck and, therefore, was more closely examined. Dynamic stresses and dynamic deflections due to traffic loads are too small to cause structural fatigue or driver discomfort. It is concluded that the proposed arch bridges over U.S. 59 in Houston should not have any problems with wind or traffic loadings.