Analysis and design of tandem vehicles and guardrail breakaway cable terminals for safer highways.

摘要

Problems related to highway safety often result in economic and, most important, human losses. Two such problems are considered herein. The first involves lateral dynamics, handling performance, and stability of two full vehicles in tandem, while the second involves present-day guardrail Breakaway Cable Terminal (BCT) systems penetrating errant vehicles upon impact. Concerning the first problem, the nonlinear equations of motion of the tandem vehicle system are derived in matrix form and then linearized. The critical forward velocity is derived in closed form, and its uncertainty and sensitivity to errors in the system-critical parameters are considered. Effects of the critical parameters (mainly the mass distribution) on the linear stability are studied, and guidelines for selecting these parameters are outlined.; Concerning the second problem, a theoretical treatment based on the plastic hinge technique is developed to determine the static plastic collapse (gross plastic failure loads and failure locations) for end-loaded, initially curved, corrugated, tapered, cantilevered beams. Effects of the end load angle, initial end displacement, and taper profile of the beam on the static plastic collapse are investigated. Effects of the elastic displacements and the change of beam geometry during loading are considered as well.; After manipulation for design purposes, this elastic-plastic treatment is applied to develop innovative terminal retrofit designs for present-day highway guardrail BCT systems. Besides low-cost and ease of installation, these retrofit designs have reduced buckling strength and favorable design features. They are initially curved away from the direction of traffic flow, have corrugated sections that interface with guardrail BCT systems, and are flared width-wise and tapered depth-wise towards the impacted end. These terminal retrofit designs can mitigate the problem of guardrail BCT systems penetrating errant vehicles upon impact, especially in cases of head-on and shallow end impacts of present-day small, light-weight passenger vehicles. As a result, safer and more efficient highways are provided.