GUARDRAIL CONNECTION FOR LOW-FILL CULVERTS

A W-beam guardrail system was developed for attachment to the top slab of a low-fill concrete culvert. The guardrail design was constructed with a single, 2.66-mm-thick W-beam rail totaling 53.34 m in length. Over the culvert, W150x13.5 steel posts 946 mm long spaced 952.5 mm on center supported the W-beam rail. The research study included dynamic testing with a bogie vehicle and steel posts attached to a rigid foundation, computer simulation modeling with BARRIER VII, and two full-scale vehicle crash tests. The crash tests used three-quarter-ton pickup trucks and were conducted in accordance with the Test Level 3 (TL-3) requirements specified in National Cooperative Highway Research Program (NCHRP) Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. The first test was successfully conducted on the guardrail system with the back sides of the posts positioned 457 mm away from the front of the culvert\u27s headwall. The second test was unsuccessfully performed on the guardrail system with the back sides of the posts positioned 25 mm away from the front of the headwall. The safety performance of the W-beam guardrail system attached to the top of a low-fill concrete culvert was determined to be acceptable according to the TL-3 criteria found in NCHRP Report 350. Recommendations for the final placement of the guardrail system with respect to the culvert headwall are also made