Structural Analyses, Design, and Testing of Retrofit Bridge Rail

Abstract

The Roy B. Inks steel truss bridge (listed in the National Register of Historic Places) over the Llano River in Llano, Texas, is approximately 794 ft in length with a posted speed limit of 40 mph. This bridge design is common to many of the historic bridges in the state. The bridge railing does not meet the current safety requirements of NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features (NCHRP Report 350) for Test Level 2 (TL-2). The railing used is attached directly to steel truss members. On the basis of structural analyses, many of these members are not adequate to resist TL-2 crash forces. The purpose of this research was to develop a retrofit bridge railing design that is crashworthy with respect to NCHRP Report 350 requirements and a design that can be used on similar historic steel bridges within Texas. Crushable pipe blockouts located between the new retrofit rail and the truss members were developed as part of this research and were used to minimize the crash forces transmitted to the steel truss members. The new rail design retains the historic appearance of the bridge. The retrofit rail design, along with a rail expansion joint developed for this project, was successfully crash tested with respect to NCHRP Report 350 TL-3 requirements. The results of this research, the new bridge rail design, and the crash test results for the new design are presented.