Research on Design and Impact Performance of Wing⁃Wall⁃Free Stiffness⁃Gradient Guardrail Transition Section

The guardrail transition section plays a crucial role in connecting concrete and steel guardrails. However， traditional transition designs incorporating concrete wing walls have disadvantages such as prolonged construction duration， high cost， and difficulty in retrofitting. To address these issues， this research proposes a wing-wall-free SB-level guardrail transition structure. This design replaces traditional wing walls by using triple W-beam guardrails， anti-blocking plates， and variably spaced posts to connect the steel and concrete guardrails， with supporting blocks ensuring a smooth stiffness change. Finite element analysis was conducted using HyperMesh and LS-DYNA， and full-scale vehicle impact tests were carried out involving a small passenger car， a medium passenger bus， and a large truck to evaluate the transition section’s containment， redirection， and energy absorption capabilities. The simulation and experimental results were consistent and met all regulatory requirements in Design Specifications for Highway Safetey Facilities（JTG D81-2017）， demonstrating that the proposed design satisfies SB-level crashworthiness standards. This study provides a design concept for wing-wall-free guardrail transition sections.