Phase III Development of a Bullnose Guardrail System for Median Applications
Bob Bielenberg, John Reid, Ronald Faller, John Rohde, Dean Sicking, Eric Keller, Jim Holloway, Lora Supencheck
The research study consisted of Phase III of the development and full-scale vehicle crash testing of a bullnose barrier concept for the treatment of median hazards. The bullnose guardrail consisted of a 12-gauge thrie beam rail supported by twenty-two wood posts, eleven posts on each side of the system. Horizontal slots were cut in the valleys of selected thrie beam sections to aid in vehicle capture as well as to reduce the buckling and bending capacities of the rail. Five full-scale crash tests were performed, using both a 2000-kg pickup truck and a 820-kg small car. The first crash test, consisting of a 2000-kg pickup truck impacting at a speed of 103.0 km/h and an angle of 13.4 degrees, was successful. The results of that test led to the system being redefined as a non-gating rather than a gating terminal. The second and third tests of the series were unsuccessful tests of an impact of a 2000-kg pickup truck on the critical impact point at an angle of 20 degrees and a speed of 100 km/h. The failure of both of these tests was due to a combination of a lack of lateral stiffness and guardrail tension that led to vaulting of the vehicle. Computer simulation was used to investigate the failed tests and aid in making design changes. Analysis of the simulation and full-scale test results led to the addition of six new posts to the system as well as the use of double, tapered blockouts, LS-DYNA computer simulation modeling of the modified design demonstrated successful containment of the pickup truck. The fourth test, impacting at a speed of 99.8 km/h and an angle of 22.3 degrees on the critical impact point was determined to be successful according to the safety standards set forth by the Test Level 3 (TL-3) evaluation criteria described in the NCHRP Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. A final test, impacting the nose of the barrier at 105.0 km/h and an angle of 15.7 degrees, was also judged successful. Based on the performance of the system under these NCHRP Report No. 350 tests as well as these previously reported, it is recommended that the bullnose barrier be approved for use on federal highway systems. Recommendations for the application of the new design were also provided.
Highway Safety, Guardrail, Roadside Appurtenances, Longitudinal Barrier, Bullnose Barrier, Crash Test, Compliance Test, Median Protection
Other files to download