GUARDRAIL IN POSTTENSIONED TIMBER-BRIDGE SPECIMEN

A semiempirical, mathematical model for assessing the load behavior of bridge guardrail systems is described. A full-scale laboratory specim en was represented by a beam supported by coupled, elastic springs. Em pirical flexibility coefficients were used to establish the spring con stants for the post and deck subassembly of the specimen. This model w as applied to a panelized, longitudinal-deck bridge specimen. Laborato ry load tests were conducted both without and with posttensioning feat ures incorporated into the specimen. Longitudinal, transverse and angu lar loads were separately applied to the specimen. The model was succe ssful at predicting transverse load-displacement behavior. A stiffenin g due to posttensioning was evident. Due to erratic load-slip behavior of the connection details, the modeling of longitudinal load-displace ment behavior was unsuccessful. The danger of a possible failure of th e guardrail post at a low load level was observed under longitudinal l oading. Loosening of the post to deck connection during the posttensio ning was a factor in the occurrence of load-slip behavior.