Manual for Assessing Safety Hardware Test Level 4 Design and Evaluation of a Restorable Energy-Absorbing Concrete Barrier

Abstract

A new, high-containment longitudinal barrier was designed to reduce the acceleration imparted to passenger vehicles during impacts and to be restorable and reusable. Elastomer support posts were designed to translate laterally and absorb energy when struck and then to restore to their initial position after impact events. A hybrid concrete beam and steel tube combination rail was optimized to minimize weight, provide sufficient structural capacity, maintain a height to contain and redirect single-unit trucks, and prevent passenger vehicles from snagging on the posts. Three full-scale vehicle crash tests were conducted according to the Manual for Assessing Safety Hardware ( MASH) Test Level 4 (TL-4) safety performance requirements on a barrier 240 ft long with nominal height of 38⅝ in. In the Safer for Highway Test 1 (SFH-1), a 5,021-lb pickup truck was redirected with minimal damage to the barrier. The peak lateral acceleration was reduced 47% compared with similar impacts on rigid barriers. In the SFH-2 test, a 2,406-lb small car was redirected by the barrier, and the peak lateral acceleration was reduced 21%compared with similar impacts on rigid barriers. In the SFH-3 test, a 21,746-lb single-unit truck was successfully contained and redirected, resulting in only minor damage to the concrete rail. Therefore, the barrier met all the MASH TL-4 safety performance criteria. The paper provides recommendations about the performance, future design refinements, and installation requirements of the barrier.

Development of a Standardized Buttress for Approach Guardrail Transitions

“…Shape transitions should be gradual to prevent vehicle instabilities. Based on previous simulation efforts, transitions to the face geometry of a rigid barrier incorporating lateral slopes steeper than 10:1 may cause stability issues ( 28 ). Thus, it is recommended to utilize a maximum 10:1 lateral slope to transition the shape of the standardized buttress, and shape transitions may begin 6 in.…”