Development of Standards for Placement of Steel Guardrail Posts in Rock.

摘要

A steel-post W-beam guardrail system was developed for installation in rock-soil foundations. The guardrail system was constructed with a 2.66-mm (12-gauge) thick W-beam rail, 53.34 m in length. The W-beam guardrail was supported by twenty-seven W152x13.4 by 1,346-mm long steel posts, spaced at 1,905 mm on center. The posts were installed in drilled holes in concrete, constructed by drilling three 203-mm diameter holes on 165-mm centers to a depth of 610 mm. The drilled holes were backfilled with compacted ASTM C33 coarse aggregate, size no. 57. One full-scale vehicle crash test, using a -ton pickup truck, was performed on the W-beam guardrail system. The test was conducted and reported in accordance with the requirements specified in the National Cooperative Highway Research Program (NCHRP) Report No. 350, Recommended Procedures for the Safety Performance Evaluation of Highway Features. The safety performance of the W-beam guardrail system with post placed in rock was determined to be acceptable according to the Test Level 3 (TL-3) evaluation criteria specified in NCHRP Report No. 350. Further, guardrail post placement recommendations were also developed for situations where rock is located below the surface. These recommendations were developed through an analysis of bogie testing of posts.