加劲肋对外伸端板连接火灾下破坏模式的影响

为研究外伸端板连接节点火灾下的破坏模式及承压加劲肋厚度对节点耐火性能及柱稳定性的影响,研究了热力耦合作用下节点的响应.采用钢结构设计理论和非线性有限元分析方法研究了节点火灾下的破坏模式、承压加劲肋的失稳及加劲肋厚度对节点耐火性能及柱稳定性的影响.结果表明:火灾下节点的破坏模式为:首先在端板和柱翼缘承拉区发生弯曲大变形,之后承压部分局部失稳并最终导致节点丧失承载力;承压加劲肋厚度对节点耐火性能有较大影响,火灾下加劲肋受到不断加大的热应力作用,但其临界应力随材料刚度退化而不断降低,较薄的承压加劲肋易发生失稳并引发柱腹板局部屈曲导致节点失效.适当增加承压加劲肋厚度可防止加劲肋的屈曲并有利于柱火灾下的稳定.

Effect of stiffener of extended endplate connection on failure mode in fire

In order to reveal the failure mode of extended endplate connections in fire and the effect of compressive stiffener thickness on the fire resistance of connection and the column stability,behaviors of the connection subjected to thermal-mechanically coupling action were investigated.Failure mode of the connection in fire,buckling of compressive stiffener,and the effect of stiffener’s thickness on fire resistance and stability of column web were investigated by finite element analysis and theories of steel structure design.The results show that the failure mode of extended endplate connection is the large deformation of bending taking place initially in the tensile zone of endplate and column flange,and then the local buckling of compressive zone in connection causes the loss of carrying load.The thickness of compressive stiffener has significant effects on fire resistance of the connection;thermal stress in the compressive stiffener increases constantly in fire,but the critical stress reduces constantly due to stiffness deterioration of the material,so smaller stiffener thickness buckles the stiffener more easily,which induces the occurring of local buckling for column web and the connection failure.The fire resistance of extended endplate connection and column stability can be improved significantly by applying larger compressive stiffener thickness.