Long-span semi-rigid cable barriers designed for high-impact severity satisfying the small car impact speed of 160 km/h

Abstract

This study attempts to develop a semi-rigid barrier that produces a dynamic lateral displacement of approximately 0.8 m for the large vehicle impact energy of 261.4 kJ (14-ton truck – 85 km/h – 15°) and satisfies the small car impact condition of 1.3 tons – 160 km/h – 20°. Through extensive finite element analyses for various alternatives, it was investigated that a cable barrier could play a role of a semi-rigid barrier and satisfied the target performance when it, into which the initial pre-stressed force of 1900 kN was introduced, employed strong posts with a post spacing of 60 m. The occupant safety of this semi-rigid cable barrier is improved when the post spacing is increased but the initial pre-stressed force of the cables and cable anchor systems had to be increased to maintain the same working width. Due to the flexible characteristics of cable barriers with long spans, the semi-rigid cable barrier showed a possibility that it could accommodate small car impact velocities higher than 160 km/h. However, the semi-rigid cable barrier also revealed a vulnerability for large vehicle impacts as its bottom rail might rotate if the installation height was not enough to accommodate the deflection of cables. The final design of the long-span strong-post semi-rigid cable barrier was verified through full-scale vehicle crash tests.