钢框架结构动力连续倒塌分析

Dynamic progressive collapse analysis of steel frame structure

采用可考虑塑性分布的梁柱单元模拟材料非线性,并建立了考虑初始变形的动力连续倒塌分析模型。通过对钢框架结构进行详细的连续倒塌分析,研究了底层柱失效时间对结构响应的影响和竖向荷载传力路径以及梁的受力机理,并对框架破坏后的连续倒塌状况进行了评估。结果表明,失效时间小于自振周期时,失效时间的长短对框架的动力响应有显著影响;局部破坏导致上部结构形成新的竖向传力路径,上部不平衡的竖向荷载由失效柱相邻的柱承担;结构在局部承重柱失效后上部梁中弯矩内力发生重分布现象,失效柱上方的梁端弯矩作用方向发生改变,且弯矩值明显增大。文中按我国规范设计的框架结构在单根柱失效的情况下不会发生连续倒塌。

Using the beam-column element considering the distributed plasticity to simulate the inelastic behavior,the model with initial deformation condition for dynamic progressive collapse analysis was constructed.Through the detailed analysis of a steel frame structure,the effect of failure time on structure dynamic response was investigated,the new vertical load path and the load-carrying mechanism of beams were analyzed,and eventually the resistance to progressive collapse of the frame was evaluated.It is shown that when the period of failure time is less than the structural nature period,the effect of failure time on structure dynamic response is obvious.A new vertical load path is created due to local damage,and the unbalanced vertical loads over local damage are supported by the columns in the vicinity of the removed column.After the column is failure,the redistribution of beam bending moment above the failure column is formed,the bending moment over the removed column reverses direction and the magnitude of bending moment increases significantly.The steel frame designed based on the codes in China has the resistance to progressive collapse when one column is removed.