MECHANICAL PERFORMANCE ANALYSIS ON U-BRAKE ENERGY DISSIPATOR USED IN PASSIVE PROTECTION NETS

U-brake energy dissipator is a new important component in the passive protection nets, which consists of a steel plate band, a cylindrical roller and a sleeve. The main function of the energy dissipator is to decrease the impact force on the anchors and cables, and to dissipate the impact energy of the rock-fall. Because there was no relevant engineering experience in the design theory and application of the U-brake energy dissipater, quasi-static tensile tests were carried out repeatedly. The results showed that:U-brake energy dissipators had better performance under the repeated tension; the starting force and the energy dissipation capacity were increased at the first tensile tests due to the plastic hardening effect of the material; the steel plate band exhibited brittle fracture similar to the fatigue failure at the fourth tensile test. Based on the related phenomena and the results of repeatedly tensile tests, the energy method was proposed for the theoretical analysis on the starting force and the energy dissipation performance. A theoretical calculation method proved by the experimental data was deduced and could be used as basis for the engineering design of U-shaped energy dissipators.