Shape Optimization of SB3-Grade Guardrail via Taguchi and Nonlinear Analysis

This study presents a structural optimization approach for reducing the maximum lateral deflection of roadside guardrails using a two-stage Design of Experiment (DoE) combined with non-linear crash analysis. Full-scale crash tests are costly and difficult to repeat, limiting their use in evaluating multiple design alternatives. To address this limitation, finite element analysis was performed to simulate the impact behavior of a three-wave guardrail under national SB3 crash test conditions, involving an 8,000 kg vehicle impacting at 80 km/h and 15°. In the first stage, a Taguchi L18 orthogonal array and analysis of variance (ANOVA) were used to evaluate seven cross-sectional shape and thickness variables. The results showed that the end waveform geometry, especially depth and radius, had a dominant influence on deformation behavior. In the second stage, a refined L9 orthogonal array was applied to optimize the critical parameters. The optimized design reduced the guardrail thickness from 3.2 mm to 2.3 mm and decreased the maximum deflection by approximately 10.0% compared with the baseline model. These results demonstrate that the proposed method can efficiently derive improved guardrail designs under limited computational resources.