Performance Evaluation of the Modified T77 Bridge Rail (0-4852-S)

The Texas Department of Transportation (TxDOT) frequently receives requests from districts and the public to provide aesthetically pleasing traffic rails for use on select bridges and roadways. Such rails are normally installed along designated scenic or historic routes and various types of urban facilities. Although aesthetic rails are generally more expensive to construct, their cost is still only 2 percent to 5 percent of the total cost of the bridge, and yet they can be the defining feature of a bridge. Typically, aesthetic rails are ornate and have an open architecture that may compromise their crashworthiness. If not properly designed, vertical and horizontal openings in these barriers provide the opportunity for vehicle snagging, which can produce undesirable decelerations or occupant compartment intrusion. Traffic barriers are frequently designed for high-speed facilities (i.e., > 60 mph), which exacerbates the potential problems presented by surface asperities. TxDOT is seeking to expand the number of aesthetically pleasing traffic rails available to the motoring public that meet NCHRP Report 350 Test Level 3 (TL-3) impact conditions. TxDOT, in response to the need for providing context-sensitive design alternatives for the public, initiated a prior project (Project 0-4288) to develop additional aesthetically pleasing rail alternatives. The Texas Transportation Institute (TTI) and TxDOT worked cooperatively to conceptualize and develop two aesthetically pleasing and crashworthy rail designs. The rails were designated the T77 and the F411. Researchers performed and evaluated full-scale crash tests on the new rails in accordance with NCHRP Report 350 test 3-11. The TxDOT F 411 bridge rail performed acceptably according to the evaluation criteria of NCHRP Report 350. However, the T77 design failed to perform acceptably when tested with a pickup Post Profile on T77 Bridge Rail. truck. Local rail deformation near the rail splice and the sleeve splice itself caused the truck to experience snag~ing and excessive occupant compartment deformation. As part of the current project, TTI and TxDOT revised the T77 design to make it perform acceptably and in accordance with NCHRP Report 350.