A NEW BRAKE ELEMENT FOR IMPACT-RESISTING FLEXIBLE BARRIER
Jian-Wei He, Zhi-Hua Zhou, Yao-Peng Liu and Siu-Lai Chan*
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China
Flexible barriers are widely employed as a protection system against rockfalls that may cause dangerous circumstances. A flexible barrier system consists of wire nets, steel cables, brake element, steel post and relevant foundations. Brake elements are the key components as they play the main role in absorbing energy generated by the impact of rockfalls and damp peak loads on the other components such as the steel cables. Hence, effective brake elements could increase the energy absorbing capacity of a flexible barrier. This paper proposes a new type of brake element consisting of a metal tube with a conjugated metal conical frustum (bullet shape). The brake element absorbs kinetic energy through the plastic deformation of the tubes and the friction generated by the contact between the bullet and the tube. A quasi-static tensile test recommended by ETAG 027 and a numerical simulation model are conducted to assess the energy absorption capacity of the brake element. The test result indicates a good performance of the brake element in absorbing energy as the braking force is constant during the braking period. A good fit of the model and test results during this period is obtained, which confirms the reliability of the finite element method as a design tool for the brake element.
Brake Element; Quasi-Static Tensile Load Test; Numerical Simulation