SERVICEABILITY MONITORING OF TIMBER GUARDRAILS ON ROADWAYS

摘要

Timber guardrail has been widely used in Japan since the newly developed timber guardrail passed the certification test. Every year more than 20 kilo-meters timber guardrails are installed on the roadways. As the increase of timber guardrail on roadways, monitoring and assessment of this kind of structures is of critical importance to their serviceability as roadway safety barriers. To assess the serviceability of the log beams used as the rails of timber guardrail, visual inspection was carried out to rate the deterioration degrees of more than 4,000 log beams of timber guardrails on roadways. Penetration depths by striker pin with strike energy of 6J were measured. Specimens of aged log beams were taken off from timber guardrails to measure the mechanical properties. Strength properties of aged timber guardrail with different degradation rating were investigated. Two full-scale collision tests by 20-ton truck were conducted on 7-year-old and 10-year-old timber guardrails, respectively. Behaviors of the 20-ton truck during the impacting process were observed and serviceability of the aged timber guardrails was confirmed.