Improvements to G4(RW) Strong-Post Round-Wood, W-Beam Guardrail System

Abstract

Strong-post round-wood W-beam guardrail, G4(RW), is a common longitudinal barrier used in Texas. Recent crash tests on the system demonstrate its effectiveness in containing and redirecting a 2,000-kg pickup truck. Even though the guardrail performed satisfactorily according to National Cooperative Highway Research Program Report 350 requirements, there were concerns about the stability of the vehicle due to excessive wheel snagging on the posts. In this study, a modification to the existing design is evaluated to improve the stability of an impacting vehicle. LS-DYNA, a dynamic, nonlinear, large deformation finite element modeling code is used to analyze and compare the performance of alternate designs. A baseline finite element model of the existing system is developed to replicate the observed crash test behavior of the G4(RW). The fidelity of the baseline model is verified against full-scale crash test results. To improve the vehicle stability, the current design was modified to include guardrail posts with shorter embedment depth. An optimum post embedment depth was determined and used in the second simulation study. Finite element analysis results show that an improved G4(RW) system eliminates wheel snagging on posts, reduces sudden vehicle deceleration and therefore improves the stability of an impacting vehicle significantly.