考虑滚石转动效应的被动柔性防护系统设计方法

Design Method of Passive Safety Net System Considering the Angular Velocity Effect of Rolling Boulders

为揭示滚石转动动能对被动柔性防护网系统力学响应的影响程度,完善既有的设计和检测方法,基于LSDYNA对被动柔性防护网结构建立了非线性动力数值模型,通过与足尺冲击试验对比,验证了数值模型参数的有效性。基于此,分析了转动动能比例系数λ对系统变形和内力响应的影响规律,提出了各构件内力峰值与λ之间的拟合关系式,并给出了考虑转动效应后各构件内力的设计修正系数ζ。研究结果表明,施加转动动能后,滚石最大竖向位移随着λ值增大而减小,滚石在水平方向上具有明显外滚趋势,上支撑绳变形明显增大;滚石冲击力和各构件的内力峰值随λ的变化规律皆可采用二次多项式表达,其中网片、钢柱、上支撑绳和拉锚绳的内力均呈现先增大再减小的趋势,当λ=0.2时达到最大值;随着λ值增大,耗能器耗能与网片耗能线性降低,同时滑移耗能与摩擦耗能线性增加。因此,滚石的转动效应会增大被动柔性防护系统中主要构件的冲击响应,设计时应充分考虑此不利影响。建议可按照既有规范中的内力放大系数赋予各构件安全储备,同时补充了钢柱的设计内力放大系数,建议取值1.3。

To reveal the influence of angular kinetic energy of rolling boulders on the mechanical response of passive safety net systems and to improve existing design and testing methods,a nonlinear dynamic numerical model of passive safefy net system was established using LS-DYNA.The effectiveness of the numerical model parameters was verified through comparison with full-scale impact tests.On this basis,the influence of the proportional coefficient of angular kinetic energy(λ)on the system deformation and internal force was analyzed.A fitting relationship between the peak internal forces of various components andλwas proposed,and a design amplification coefficient(ζ)for the internal force considering the rotational effect was provided.The results showed that after applying rotational kinetic energy,the maximum vertical displacement of the boulders decreased as theλvalue increased,and the boulders exhibited a clear outward rolling motion in the horizontal direction,with a significant increase in deformation of the upper support rope.The impact force of the boulders and the peak internal force of the components followed a quadratic polynomial relationship withλ.The internal force of the netting,steel column,upper support rope,and anchor rope initially increased and then decreased,reaching their maximum whenλ=0.2.Asλincreased,the energy absorption of both netting and dissipators decreased linearly,while the energy dissipated by sliding and friction increased linearly.Therefore,the angular velocity effect of rolling boulders increased the impact response of the main components in the passive safety net system,and this adverse effect should be fully considered in design.It was suggested to apply the internal force amplification coefficients specified in existing standards to provide safety reserves for the components,while also adding a design internal force amplification coefficient for the steel posts,with a recommended value of 1.3.