竖向刚度不同的混合结构连续倒塌机制分析

Progressive Collapse Mechanism of Hybrid Structures with Different Vertical Stiffness

为了探究上部钢结构-下部混凝土结构这类竖向刚度不同的混合结构抗连续倒塌机制,利用拆除构件法,应用ANSYS/LS-DYNA对初始失效后的剩余结构进行非线性静力(Pushdown方法)分析,研究其剩余结构的倒塌破坏模式、荷载变形关系,以及初始失效柱位置的不同和钢框架层数对结构抗连续倒塌性能的影响。结果表明:剩余结构的倒塌破坏模式带有典型的延性变形特征,且在倒塌过程中出现位移和应力分布不连续现象;除边柱失效后剩余结构的倒塌过程仅经历了梁机制外,其余剩余结构的倒塌过程均经历了梁机制、压拱机制和悬链线机制;剩余结构的竖向承载力与初始失效柱高度呈负相关,与钢框架层数呈正相关;为剩余结构提供足够的侧向约束作用以及提高结构冗余度和备用荷载路径数量,可以有效提高剩余结构的抗连续倒塌能力。

To investigate the antiprogressive collapse mechanism of hybrid structures with diffe-rent vertical stiffness values,remaining structures with initial failure are subjected to nonlinear static analysis,also known as the Pushdown method,through the alternate path method with ANSYS/LS-DYNA.The collapse failure mode of remaining structures,the relationship between load and deformation,the influence of the different positions of the initial failure column,and the number of steel frame layers on the antiprogressive collapse performance of the structure are analyzed.Results show that the failure mode of the remaining structures during collapse is characte-rized by typical ductile deformation and discontinuous displacement and stress distribution.Only the collapse of the remaining structure with side column failure experiences the beam action mechanism.By contrast,all other remaining structures experience the beam action mechanism,compressive arch action,and catenary action.The vertical bearing capacity of the remaining structure is negatively correlated with the height of the initial failure column and is positively correlated with the number of steel frame layers.The antiprogressive collapse capability of the remaining structure can be effectively improved by providing sufficient lateral restraint and increa-sing the number of alternate load paths in the remaining structures.