Numerical simulation of single- and double- faced W-beam guardrails under vehicular impacts on six-lane divided freeways

W-beam guardrails are safety devices installed on highway medians to prevent cross-median crashes. For six-lane, 46-foot median divided freeways, the paved shoulder policy requires two 12-foot median shoulders, which reduce the width of median ditch to 22 feet. For positive pavement drainage consideration, the median slope should be changed to 4H:1V, which exceeds the optimal 6H:1V slope for placing median barriers. As a practical solution, design engineers often place two lines of W-beam guardrails on the two median shoulders. While effectively preventing cross-median crashes, the two lines of guardrails create great difficulty for vegetation maintenance, e.g. mowing. There is a practical need to investigate the feasibility of replacing the two lines of single-faced guardrails with a single line of double-faced W-beam guardrail. In this study, nonlinear finite element (FE) analysis is utilized to evaluate the performance of singleand double-faced W-beam guardrails under vehicular impacts on a sixlane, 46-foot median divided freeway. Detailed FE models of the W-beam guardrails and the vehicle are presented. Various modelling issues involved in the nonlinear FE analysis such as contact modelling are discussed. Based on FE simulation results, a new double-faced W-beam guardrail is proposed and evaluated. The new design is shown to have improved performance over both the initial double-faced guardrail and the single-faced guardrail.