Performance Level 1 Tests on the Nebraska Open Concrete Bridge Rail
Ronald Faller, Jim Holloway, Brian Pfeifer, Barry Rosson
A safety performance evaluation of the 29-in. Nebraska Open Concrete Bridge Rail was conducted for the Nebraska Department of Roads (NDOR). The evaluation included computer simulation modelling and two full-scale vehicle crash tests. The two crash tests were conducted to evaluate structural adequacy of concrete posts adjacent to a gap and the reduced reinforcement in the concrete rail, respectively. The bridge rail design incorporates a 3-in. expansion gap. The NDOR Bridge Division was concerned that lateral deflections in the posts and attached rail could be of sufficient magnitude to cause vehicle snagging at the location of the gap. The bridge rail has been previously constructed in actual installations using six No. 6 longitudinal reinforcing bars. However, the NDOR Bridge Division reasoned that the structural adequacy of the concrete rail could be maintained while reducing the reinforcement from six No. 6's to six No. 5's for economic considerations. BARRIER VII computer simulation modeling of the original bridge rail design was used to predict safety performance prior to crash testing and to modify the original design. The installation went through a number of redesign phases as a result of the computer simulation modelling. The final design (Design No. 4) consisted of 11-in. x 36-in. concrete posts adjacent to the gap, and 11-in. x 24-in. concrete posts at all other locations. The safety performance evaluation was conducted and reported according to the criteria specified in the Recommended Procedures for the Safety Performance Evaluation of Highway Appurtenances, National Cooperative Highway Research Program (NCHRP) Report 230, and the American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications for Bridge Railings, 1989. The first test (Test NEOCR-1), was conducted 5-ft 10 1/2-in. upstream from the centerline of the 3-in. gap. The test was conducted with a 5,300-lb test vehicle at the impact conditions of 47.7 mph and 20 degrees. The safety performance of the 29-in. Nebraska Open Concrete Bridge Rail near the 3-in. expansion gap was determined to be satisfactory according to the AASHTO Performance Level 1 Guide Specifications. The second test (Test NEOCR-2), was conducted to evaluate the reduction of longitudinal reinforcement in a continuous concrete rail section. The test was conducted with a 5,390-lb test vehicle at the impact conditions of 45.9 mph and 20 degrees. The location of impact was at a midspan location along the continuous rail section. The safety performance of the 29-in. Nebraska Open Concrete Bridge Rail with No. 5 longitudinal reinforcement was determined to be satisfactory according to the AASHTO Performance Level 1 Guide Specifications.
Highway Safety, Roadside Safety, Bridge Rail, Concrete, Crash Test, NCHRP 230, Computer Simulation, Barrier VII, Compliance Test, AASHTO, PL-1, Longitudinal Barrier
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