Abstract
Guardrail-strengthening techniques were assessed by full-scale crash testing according to Service Level 2 conditions of NCHRP Report 230 and by BARRIER VII computer simulation. The Kansas Department of Transportation's standard W-beam with steel posts guardrail was strengthened by nesting the W-beam and by reducing the post spacing. Computer simulations with BARRIER VII were used to assess the various strengthening techniques for guardrails with standard and extended post lengths installed in clay and sand. The soil-post stiffness parameters used in the program were obtained by conducting 21 post impact tests with a 1388-kg bogie striking a post at 33 km/hr. The guardrails constructed with W6 × 8.5 steel posts and 15.2 × 20.3-cm timber posts behaved similarly under all test conditions. The density of the clay has a profound effect on the lateral dynamic deflections. Nesting the W-beam to strengthen the guardrail provides very little benefit, whereas reducing the post spacing by half provides the greatest benefit.
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