Evaluation of rail height effects on the safety performance of W-Beam barriers

The objective of this study is to investigate the effect of rail height on the safety performance of G4(1S) w-beam guardrail systems. The study involved three steps. In the first step, a detailed finite element model of the G4(1S) guardrail system was created. The model incorporated the details of the rail, connections, the post, the blockout, and the soil in which the post was embedded. To validate the model of the wbeam guardrail system, a model of the setup of this w-beam system in previous fullscale crash tests was created. Simulations were performed using this model and the results were compared to the full-scale crash test data. The results were similar indicating that the model was an accurate representation of the actual system. In the second step of the study, the validated model served as the basis for four additional models of the G4(1S) guardrail to reflect varying rail heights. In two of the four models, the rails were raised 40 and 75 mm (1.5 and 3 inches). In the other two models, the rails were lowered 40 and 75 mm. Simulations with these four new models were carried out and compared to the first simulation to evaluate the effect of rail height on safety performance. The simulation results indicated that the effectiveness of the barrier to redirect a vehicle is compromised when the rail height is lower than recommended. The third step of the study consisted of performing full-scale crash tests with the guardrail at standard height and 60 mm (2.5 inches) lower. The data from the crash tests validated the simulation results.