Large plastic deformation of W-beams used as guardrails on highways

This paper examines the large plastic deformation and failure of guardrail steel beams under quasi-static bending. Experiments were carried out for symmetric bending of steel guardrail beams to observe the global load-deflection characteristics, as well as the distortion of cross-sections. The effect of the supporting condition in three-point bending on the global behaviour of the guardrail beams was also examined experimentally. Based on the deformation mechanism observed from the experiments, a rigid-plastic analytical model which involves stationary and rolling plastic hinges is presented to calculate the collapse load as well as the bending moment vs. average curvature curve for simply supported guardrail I beams. The results thus obtained compare well with the experiments.