Critical Impact Point for Longitudinal Barriers

Abstract

A procedure for identifying critical impact points (CIP) for longitudinal barriers is presented. The procedure is based on computer simulations of longitudinal barrier impacts using the Barrier VII computer program. Critical impact points were selected to maximize wheel snagging and rail tensile loadings. The procedure is based on the finding that the critical impact point is largely dependent on the strength of the posts and the rail bending strength. Thus, the CIP selection procedure relies only on the effective post yield force per unit barrier length and the rail plastic moment. The technique can be applied to all post and beam barriers as well as transitions involving one of these types of barriers. This procedure has been incorporated into the National Cooperative Highway Research Program (NCHRP) Report 350.