Investigation of the effects of concave and convex conditions of steel guardrails built into curve on the safety parameters in accordance with EN 1317 standard through finite element analysis

When designing barriers for roadside safety, the safety parameters and performance of barriers are typically determined based on the straight condition of the road in the literature and existing studies. The curved condition (convex and concave) of the road is not taken into account. The curved condition and parameters of the road have a significant impact on road safety. The curved condition of the road is strongly related to speed. This curved road condition will cause a change in the contact time of the vehicle with the barrier during a crash compared to the straight road condition. Consequently, the acceleration and velocity values of the vehicle at the moment of impact will also change. According to EN 1317, many safety parameters are calculated based on these acceleration values. In this study, the adequacy of safety parameters for the EN 1317 TB11 test was investigated using the finite element program LS-DYNA. Fourteen different guardrail systems with convex and concave radii were designed, and collision tests were conducted using LS-DYNA. The effects of the guardrails designed according to the curved condition of the road on ASI and other parameter values were also investigated within the scope of the thesis. Initially, finite element analysis was conducted for the H1W4-A steel barrier system using a 900 kg vehicle in the TB11 test. The analysis results were then compared with data obtained from collision tests conducted in the literature under straight road conditions for validation purposes. Critical results were obtained for the convex guardrail system in the validated analyses. Especially higher and critical values for ASI and THIV safety parameters were identified compared to the straight road condition. However, critical values were not identified for the width and exit angle parameters compared to the straight road condition. For the concave guardrail system, lower values for ASI and THIV were observed compared to the straight road condition. Similar values were found for exit angle and width parameters compared to the straight road condition.