平面张弦结构抗连续倒塌的动力分析

Dynamical analysis of progressive collapse in planar string truss structure

杆件由于爆炸、腐蚀等发生脆性破坏后引起剩余结构的振动和压杆由于失稳过程中的弹性突跳(Snap-through)引起的相邻结构振动是张弦结构倒塌过程中常伴生的两种动力现象。本文对第一种动力响应产生的原因、失效构件的模拟方法进行了分析,说明进行张弦结构抗连续倒塌的动力分析应采用初始条件法模拟构件的失效。根据张弦结构的特点,从构件失效和结构失效两方面提出了张弦结构倒塌失效的评估准则,并采用变换荷载路径法通过静力连续倒塌分析找出张弦结构各部分的关键构件;然后采用初始条件法按考虑几何非线性、阻尼比、材料非线性等分别模拟这些关键构件失效引起的动力响应,得到了平面张弦结构各部分构件失效的动力特性、动力放大系数和失效构件的位置,并对不同失效时间进行动力响应分析得到张弦结构动力效应与构件失效时间的关系曲线。最后给出张弦结构进行抗连续倒塌分析的一些结论和建议,如进行连续倒塌动力时程分析时初始失效杆件选取和失效时间取值以及弹性动力放大系数与塑性动力放大系数的区别等,为张弦结构的抗连续倒塌设计提供技术支持和参考。

Two dynamic behaviors are usually observed during the process of collapse: one is the vibration of residual structures after the brittle failure of members caused by blast,erosion and etc.;another is the vibration of adjacent structures caused by 'snap-through' when strut bar being buckled.At the first part of the paper,a brief introduction on characters of two typical dynamic responses is provided.Based on the analysis on the reason of dynamic response and simulation of member failure,the effectiveness of the method of initial conditions in the dynamic analysis for progressive collapse in string truss structures is illustrated.Then the evaluation rules is put forwarded on collapse failure from two aspects of member failure and structure failure based on characteristic of string truss structure and critical members in string truss structures during progressive collapse are got through static analysis by the alternate load path method.After that,dynamic response of the structure caused by critical members is simulated by the method of initial conditions by considering geometrical nonlinear,material nonlinear and damping.From the simulation,dynamic character,magnification coefficient and location of failed members are derived,and furthermore,the curve between dynamic effect and time to failure of the strut is derived.Finally,recommendations such as initial disabled member selection,member failure time decision and the difference of dynamic amplifying effect for elastic and plastic materials,etc.,are provided to guide future dynamic analysis and design on how to prevent progressive failure in planar string truss structures.