Development of a crash energy absorber

Abstract

A new energy absorbing cartridge, named the "Z-tube" was developed for use in a new conceptualized highway safety appurtenance. The Z-tube was developed to provide a low cost method of dissipating the kinetic energy of errant motor vehicles. The Z-tube when impacted collapses in a controlled manner such that the reactive force is constant throughout approximately 70 percent of the tube's overall length. Vehicular energy is dissipated by locally buckling the walls of a series of contiguous metal tubes separated by polyethylene. The result for an impacting vehicle is a smooth, constant deceleration throughout the crash event period. A conceptual concrete safety-shaped median barrier end terminal was designed to utilize the Z-tube cartridge. Furthermore, an analytical model was developed to simulate and analyze the events of a 820 kg (I 800 lb) and a 2000 kg (4400 lb) vehicle impacting the conceptualized end terminal at 100 km/h (62 mi/h). The model was used to aid in properly selecting among the infinite number of combinations of terminal segment weights, lengths, and quantities along with the Z-Tube stiffness.