Rational analytical method to design a yielding highway traffic barrier for use on and near a bridge structure

Abstract

In this study, safety is considered to be of utmost importance in the design of at traffic barrier on and near a bridge. This paper presents an analytical method to assist the highway engineer in the rational design of a traffic barrier which, when struck, will safely redirect an out-of-control passenger vehicle by means of controlled yielding. Controlled yielding is effective in reducing vehicle decelerations to a tolerable level that an unrestrained occupant can sustain without serious injury. The analytical method is based upon an energy balance concept. During a barrier collision, a vehicle undergoes some change in its kinetic energy. This change in vehicle kinetic energy is accounted for by taking into consideration: (a) the energy dissipated in friction between the vehicle and barrier, (b) the energy absorbed by the vehicle in sheet metal crushing and deformations of the wheel or the engine firewall corner support post, and (c) the energy absorbed by the main structural elements of the yielding barrier. The energy balance method is a practical design tool. The method provides a means to determine the effectiveness of the individual yielding barrier elements by a comparison of the amount of energy absorbed by each individual. To illustrate the practicality of the energy balance method as an analytical and design tool, an example problem of an innovative yielding barrier concept is presented. This barrier is designed to safely redirect a selected automobile under in-service impact conditions, and to restrain a large automobile and truck under currently accepted test impact conditions..