Lightweight design and post-impact attitude stability of extra-high grade guardrail based on 700L high-strength steel

To address the issues of excessive self-weight and insufficient post-impact attitude stability inherent in traditional HA-level (extra-high grade) beam-post guardrails due to oversized cross-sections, this paper proposes a lightweight design method utilizing 700L high-strength alloy steel. Through topology optimization, a novel guardrail structure comprising “inclined H-shaped posts” and “rectangular tube beams” was developed. Full-scale vehicle crash tests show that under the HA-level heavy-vehicle impact matrix specified in JTG B05-01–2013—namely a 25 t extra-large passenger bus, a 40 t heavy truck, and a 55 t tractor-semitrailer—the guardrail’s containment and redirection functions meet the corresponding HA-level heavy-vehicle requirements. None of the three vehicles rolled over, overrode, or straddled the guardrail, and all exited with stable post-impact attitude. Vehicle lateral intrusion is substantially reduced: under the 55 t tractor-semitrailer collision condition, the maximum dynamic equivalent vehicle lateral intrusion value (VIn) is reduced by 64.2% compared with conventional guardrails. In terms of lightweight design, the weight per linear meter of the guardrail is decreased from 230 kg to 180 kg, representing a reduction of 21.7%. Economic analysis shows that the reduction in material consumption lowers the overall material cost by approximately 10%–15%. This study demonstrates a material-structure co-design method that simultaneously improves safety, lateral intrusion resistance, lightweight level and economy for HA-level heavy-vehicle conditions, providing a theoretical basis and technical support for the engineering application of a new generation of high-performance bridge guardrails.