Abstract:
The structural failure of post-and-beam W-beam guardrails during impact sometimes results from the rupture of the W-beam rail at splice connections. This study examines the mechanics of these failures to identify their causes and formulate a design alternative to reduce the likelihood of rupture. The investigation considered the tensile forces in the W-beam rail and the deformation mode of the splice connection during impact. Using a combination of full-scale crash tests, laboratory tests, and finite element analysis, the research determined that failures at splices are not caused by exceeding the axial capacity of the guardrail but rather by complex multi-axial strains experienced when splices are located at guardrail posts. The finite element analysis, using LS-DYNA and a detailed submodel of a single guardrail post and a spliced W-beam, revealed that high stress concentrations and plastic hinges form around the bolt holes in the back layer of the W-beam. This analysis predicted a tear path that matches observations from full-scale tests, starting at the bottom downstream hole and propagating through the cross-section. The study concludes that relocating splices to the mid-span of the guardrail, where they experience less complex stresses, would significantly reduce the chance of rupture.
