Development and structural testing of a composite-reinforced timber highway guardrail

Various government agencies install timber guardrails on scenic highways and roads in lieu of conventional steel guardrails for aesthetic reasons. Most acceptable timber guardrails rely on a continuous steel backing member to carry the large tensile forces caused by vehicle impact and transfer load to the posts. However, these guardrails are relatively expensive and heavy due to their use of large, solid-sawn timber sections. This study focuses on the development and structural testing of a novel timber guardrail that consists of a hardwood glued-laminated member strengthened with a fiber-reinforced polymer (FRP). The FRP acts in place of steel to carry the impact-induced tension and the guardrail is significantly shallower and lighter than conventional timber guardrails. This paper details the analysis of the guardrail response under vehicle impact, the development and testing of a unique and easily installed rail-to-rail field splice connection capable of carrying the tensile forces caused by vehicle impact, and the evaluation of guardrail durability in exterior conditions. In addition, the structural performance of the guardrail was assessed using experiments that produced the simultaneous tension and flexure forces expected during vehicle impact using a single hydraulic actuator and a three-point bending test apparatus. Based on the development and testing documented in this paper, the FRP-reinforced timber guardrail is expected to be capable of passing required vehicle crash tests.