Design Method of Passive Safety Net System Considering the Angular Velocity Effect of Rolling Boulders
To reveal the influence of angular kinetic energy of rolling boulders on the mechanical re-sponse 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 effec-tiveness 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 sys-tem deformation and internal force was analyzed.A fitting relationship between the peak internal forc-es of various components and λ was 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 the λ value 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 inter-nal force of the components followed a quadratic polynomial relationship with λ.The internal force of the netting,steel column,upper support rope,and anchor rope initially increased and then decreased,reaching their maximum when λ=0.2.As λ increased,the energy absorption of both netting and dissi-pators decreased linearly,while the energy dissipated by sliding and friction increased linearly.There-fore,the angular velocity effect of rolling boulders increased the impact response of the main compo-nents 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 co-efficient for the steel posts,with a recommended value of 1.3.
passive safety net systemnumerical simulationangular kinetic energydynamic response characteristicsdesign method
万方数据
维普
