An evaluation method for quantifying the residual performance of flexible rockfall barriers after impact

Abstract

Currently, there is no effective analysis algorithm to calculate and evaluate the residual performance of flexible barriers after suffering rockfall impact. To solve this problem, a novel approach for assessing and quantifying the residual performance of flexible barriers through the deflection degree of different components is proposed, based on the substantial experimental database from impact tests that were conducted with impact energies between 750 kJ and 1500 kJ, revealing a high correlation between the three-stage macroscopic deflection characteristics and the residual performance. The approach consists of two significant aspects, one is the calculation method of the residual protection capacity, which was established according to the simplified calculation method of the energy dissipation of the dissipators. The other aspect is the damage identification method for the barrier system based on the deflection of key components, which was determined by comparing the deflection angle of the post and the punching deflection of the net obtained from the analytical geometric model with the ultimate deflection of those components calibrated by tests. Utilizing the ultimate force-deflection relationship calibrated by tests, a method to discriminate the system damage based on the analytical calculation value of the deflection of key components is established. Furthermore, both full-scale tests and numerical simulations were conducted to validate the proposed analytical calculation method. The tested flexible barrier had a nominal energy level of 2000 kJ, and the tests included service energy level (SEL) and maximum energy level (MEL) continuous impacts. The analysis results show that the maximum calculation errors for the energy dissipated by the energy dissipators, elongation of the energy dissipator, elongation of the wire ring, and out-of-plane deflection angle of the post are -3%, 10%, 12%, and -8%, respectively. The evaluation results of the residual performance as well as the damage identification both have satisfied agreement with the test results, confirming the reliability and applicability of the analytical method to engineering maintenance decisions.