落石被动柔性防护网冲击力学响应的参数化研究

Parametric study on the mechanical response of a flexible rockfall barrier

针对落石被动柔性防护网的试验检验仅采用特定冲击条件,未能有效反映实际可能存在的最不利工况,从而导致通过试验检验的产品在实际工程应用中未能有效实现预期防护目标的现状,采用数值计算方法对不同参数条件下落石被动柔性防护网的力学响应开展了深入研究。首先,基于LS-DYNA软件,反演了某配置有辅助支撑绳的5000 kJ落石被动柔性防护网的足尺冲击试验,对比分析了缓冲距离、关键绳索内力及耗能器伸长量,校验了计算模型。在此基础上,分别针对跨数、落石冲击位置、柱端滑移特征对被动柔性防护网支撑绳内力、钢柱内力及缓冲距离等力学响应的影响开展了参数化分析。结果表明:跨数对被动柔性防护网力学响应影响较小;相同冲击条件下,边柱内力是中柱的2倍以上,且受冲击位置影响显著,边跨冲击最为最不利,通过标准试验检验的系统在边跨受到冲击时边柱仍可能屈曲;柱端滑移摩擦因数的增加使得支撑绳内力增长显著,建议支撑绳设计时安全系数不小于2.0。

Only specific impact condition is considered in verification tests of flexible rockfall barriers,which may not be the worst-case scenario in practice.Field investigations show that part of the products which pass the verification tests do not effectively achieve the expected protection target.Therefore,an in-depth research on the mechanical response of a flexible rockfall barrier under different impact conditions was carried out by numerical simulations.Firstly,the full-scale impact test of the flexible rockfall barrier with auxiliary supporting ropes was back-analyzed.The numerical model was verified by comparing the breaking distance,rope forces,and the elongation of energy dissipators.On this basis,parametrical simulations were carried out to investigate the effects of span number,impact location and post ends sliding characteristics on the mechanical response of the flexible rockfall barrier.Results show that:the mechanical response of the flexible rockfall barrier was less affected by the number of spans;under the same impact condition,the internal force of the side post was more than twice that of the middle steel post,and was significantly affected by the impact location.In term of the side post,the impact position located at the side span is most unfavourable,and it may buckle even when the system passed the standard verification test;the internal force of supporting ropes will grow significantly with the increasing of the friction coefficient of post ends,and a safety factor of 2.0 was recommended for the design of supporting ropes.