被动柔性防护网结构的累计抗冲击性能研究

Cumulative impact resistance of passive flexible protective structure

针对被动柔性防护网在实际工程中承受累计冲击的现状,开展标称能级为1 500 kJ的防护网结构足尺落石试验,在无修复状态下进行连续累加冲击;基于LS-DYNA的显式算法,对试验进行全过程模拟;进而采用数值分析开展标称能级为750,3 000和5 000 kJ系统的累计冲击模拟。结合试验与数值仿真研究累计冲击作用下,结构的传力机制、变形特征、耗能分布。结果表明:中跨已成功拦截1 500 kJ落石冲击的被动柔性防护网,仍具有继续承受左跨750 kJ、右跨750 kJ和中跨1 500 kJ共4次连续冲击能力。系统的冲击力学行为具有明显的三阶段特征,随着累计冲击的开展,系统的主要耗能由第二阶段转换为第三阶段;减压环的耗能比例降低,网片的耗能比例提高;结合各工况的性能曲线,建立系统的能量储备系数与各阶段能量比例的相关计算公式,采用该公式可对系统的能量储备进行预估,研究结果为被动柔性防护网结构的设计提供理论基础。

The continuous cumulative impact with the nominal energy level of 1 500 k J in the full scale rockfall test on the passive flexible protective structure was carried out. The whole process of test was simulated with the explicit algorithm of LS-DYNA. The cumulative impact of nominal energy levels of 750,3 000 and 5 000 k J system was simulated numerically. The transmission mechanism, deformation characteristics and energy dissipation distribution of the structure under the cumulative impact were studied experimentally and numerically. While the middle span of the structure has successfully intercepted the rock fall of 1 500 k J,the left and right span can still bear the consecutive impacts 750 k J four times and the middle span 1 500 k J four times. The impact behavior of the system has distinctive characteristics of three stages. With the development of cumulative impact,the main energy consumption of the system transits from the second stage to third stage. The proportion of energy consumption of the brake ring is reduced,and that of the net is raised. The formula for the coefficient of energy reserve of the system is established according to the performance curve under each working condition.