A cumulative damage model based on deformation-energy parameters for flexible barriers under multiple repeated impacts

Existing flexible rockfall barrier systems are frequently exposed to repeated rockfall impacts during use, yet research addressing the cumulative damage sustained by these systems remains limited. A novel numerical simulation method is proposed to study the effects of repeated impacts on flexible barrier systems, which considers the damage and deformation accumulation of components through a complete restart method. Two full-scale sequential impact tests were conducted to validate this numerical simulation method's effectiveness. The impact conditions for both tests were service energy level (SEL). The deformation behavior and energy dissipation mechanism of the flexible barrier system subjected to repeated impacts were examined. The findings indicate that the net serves as the primary component undergoing deformation during rockfall impacts, with the residual deflection of the wire-ring net accounting for approximately 61 % and 58 % of the system's overall residual deflection in the respective tests. Furthermore, the energy dissipators emerge as the principal components responsible for energy dissipation, constituting approximately 71 % and 64 % of the system's energy dissipation in the two tests, respectively. Considering that both the net and the energy dissipator are key components influencing the barrier system's ability to withstand rockfall impacts, they are also prone to experiencing the most severe damage. Methods for calculating the damage of the components have been devised. The residual deflection of the wire-ring net and the energy dissipated by the energy dissipators are employed as parameters for assessing damage. A method for estimating structural damage is developed using a two-parameter model for deflection and energy dissipation. A parametric analysis was conducted to evaluate the performance of the flexible barrier system under repeated impacts spanning impact energies from 100 kJ to 2000 kJ. The cumulative damage in both the barrier and its components is thoroughly investigated. A simplified criteria for assessing cumulative structural damage incurred as the barrier undergoes multiple repeated impacts is proposed. The study findings indicate a linear relationship between the number of impacts and both component and structural damage, with the slope of this relationship positively correlating with impact energy. Structural damage can be characterized by damage of the net and the energy dissipators, with the latter as the primary influencing factor. The findings presented in this paper offer valuable insights for informing engineering maintenance decisions.