强震作用下边框架柱激发失效后混凝土结构接触-碰撞响应模拟

SIMULATION OF CONTACT-IMPACT RESPONSES IN CONCRETE STRUCTURES EXCITED BY SEVERE EARTHQUAKES WITH THE CONSIDERATION OF LOCAL FAILURE TRIGGERED BY SIDE COLUMNS

结构连续倒塌大多由柱失效引起,而框架结构中边柱断裂失效后悬链机制发展不充分,更易引起上部结构局部坍塌,引发构件之间的接触-碰撞,甚至导致结构整体倒塌。对强震下边框架柱激发失效的接触-碰撞响应进行动力时程分析,分析中将主从节点建模技术应用于Open SEES分析模型,运用约束处理法计算考虑构件突然失效时的动力效应,采用非线性Hertz-damp模型对边跨坍塌行为进行碰撞力学建模,程序中产生的机构通过构件移除来实现。利用外部的MATLAB程序调用Open SEES求解器计算得到的数据来计算碰撞力,并将其作为反作用力作用于Open SEES中的主结构模型,计算碰撞力和地震动联合作用下损伤结构的动力响应。研究发现:边柱断裂后引起的局部机构对下部梁的剧烈冲击可能导致下部结构的破坏,考虑接触-碰撞行为后,结构的水平位移、竖向位移、失效路径甚至倒塌模式都有显著的变化。

Column＇s failure can account for most of progressive collapse of structures. Loss of side columns in concrete frame structures would be apt to local collapse of upper floors,contact-impact among failed components,and even global collapse since catenary action cannot be fully developed in this situation. Dynamic time history analysis of contact-impact responses in concrete frame structures excited by severe earthquakes with the consideration of local failure triggered by side columns was carried out by using Open SEES in which the master-slave node modeling technique was applied. The restraint treatment method was used to capture dynamic responses resulting from sudden failure of components. Contact-impact behavior in local collapse process due to loss of side columns was described by using the nonlinear Hertz-damp model. Mechanism generated from analytical program was simulated through removal of damaged components. An external MATLAB-based program was employed to determine impact forces with the analytical data from Open SEES solver. And,these internal forces were applied as external forces on damaged main structural model in Open SEES to calculate dynamic responses of the structure applied with combined impact forces and earthquake excitations. The results from an example indicated that local mechanism formed in upper structure due to loss of side columns would lead to substantial impact on lower beams,possibly cause failure of lower structure.With the consideration of contact-impact behavior,the responses in structures can exhibit significant variation in predicting horizontal displacement,vertical displacement,failure path and even collapse pattern.