Dynamic behavior and safety assessment of vertical fall-arrest system with flexible tracks for transmission tower under falling impact load

This paper focuses on the dynamic behavior and safety assessment of vertical fall-arrest system with flexible tracks for transmission tower under falling impact load. Thirty drop tests were conducted using different test methods with different falling heights and hanging-board thicknesses. The dynamic behavior of the fall-arrest process was primarily researched, and the force–time curves of the flexible track and rope were obtained by tests. Furthermore, the strain of the hanging board and the rope grab during the fall were investigated, and energy dissipation and safety assessments were carried out. Finally, an energy balance calculation method based on the dynamic nonlinear stiffness of the rope was proposed to calculate the fall displacement and maximum impact load of the works. The results showed that the vertical fall-arrest system could extend the load-bearing time of workers through the deformation of the track and rope grab, thereby reducing the maximum impact force on them. However, vertical fall-arrest systems still pose safety risks, and the impact loads on workers often exceed the safety limits. The effect of the impact load on the material stiffness cannot be ignored, and it is unreliable to only conduct static analysis to predict the impact force and displacement of workers. The proposed energy balance calculation method based on the dynamic nonlinear stiffness has good accuracy. The research results can provide a reference for the dynamic behavior calculation and design of fall-arrest systems to further reduce the occurrence of falling accidents and for the construction and maintenance of transmission towers.