Crash performance of strong-post W-beam guardrail with missing blockouts

Abstract

Missing blockouts in a strong-post w-beam guardrail, a condition most commonly associated with environmental decay or crash damage, has never been thoroughly investigated. To determine the risks posed by the removal of a blockout, a combination of component-level pendulum testing and full-scale finite element models of crash tests was used to assess whether a missing blockout renders the guardrail performance unacceptable. Finite element models were developed for three pendulum tests. (1) A 30.1-kph impact into a test installation with proper blockout installation resulting in containment, (2) a 30.5-kph impact into a test installation with one missing blockout resulting in splice rupture, and (3) a 26.7-kph impact into a test installation with one missing blockout resulting in containment. The finite element model was able to reproduce the splice failure in test 2 when the appropriate mesh quality and failure criteria were used. Full-scale crash test models of a 2000-kg pickup truck striking a 29 post guardrail at 25° were developed. The simulation results indicated that wheel snagging was not a major problem. Although a missing blockout increases the maximum rail tension and deflection by as much as 13%, such guardrails are still capable of safely redirecting of vehicles.