Phase IV Development of a Short-Radius Guardrail for Intersecting Roadways

摘要

This research study consisted of the development and testing of a short-radius guardrail system for protection of hazards near intersecting roadways and capable of meeting the Test Level 3 (TL-3) impact conditions of the Update to NCHRP Report No. 350 criteria. A short-radius system was designed and consisted of a curved and slotted thrie beam nose section with two adjacent slotted thrie beam sections supported by breakaway posts. One side of the system was attached to a TL-3 steel post approach transition while the other attached to a TL-2 end terminal. Two full-scale crash tests were conducted on the short-radius guardrail system. Both tests were conducted at the proposed Update to NCHRP Report No.350 Test Designation 3-33. As such, the impacts were oriented at an angle of 15 degrees to the roadway, and were to occur at the center of the short-radius nose section. In test SR-7, a 2,263-kg (4,989-lb) pickup truck impacted the short-radius with its center aligned with the centerpoint of the nose section at aspeed of 100.3 km/h (62.8 mph) and at an angle of 18.1 degrees. The pickup truck was captured by the short-radius system, but the vehicle overrode the thrie beam guardrail and subsequently rolled over. This test was judged unacceptable according to the Update to NCHRP Report No. 350 criteria due to vehicle rollover. Following the failure the short-radius system was modified by increasing the size of the transverse holes in post no.'s 1S, 2S, and 1P, adding washers to post no.'s 1S, 2S, 1P, 2P, 3P and 4P, redesigning the cable anchor bracket on post no. 1P, and reducing the width of the outer slot tabs in the nose section. In test SR-8, a 2,268-kg (5,000-lb) pickup truck impacted the short-radius guardrail with its center aligned with the centerpoint of the nose section at a speed of 101.3 km/h (62.8 mph) and at an angle of 17.9 degrees. Once again the pickup truck was captured by the system, but the vehicle overrode the thrie beam guardrail. This test was judged to be unacceptable according to the proposed Update to NCHRP Report No. 350 criteria due to vehicle override of the guardrail. After review of the full-scale tests, it was evident that the short-radius guardrail system showed significant improvement over the original system developed by the Midwest Roadside Safety Facility, but further development is required.