拉剪组合作用下平齐端板节点火灾行为的有限元分析

FEM ANALYSIS OF FLUSH ENDPLATE CONNECTIONS UNDER THE COMBINED EFFECT OF TENSION AND SHEAR IN FIRE

常温竖向荷载作用下平齐端板节点以承受剪力为主,高温下的大变形导致梁内产生巨大的悬链拉力,节点通常在拉剪共同作用下发生破坏。采用通用有限元软件ABAQUS建立平齐端板节点的三维实体分析模型,考虑材料的非线性及节点大变形的影响,模型建立了各部件间显式的接触关系。采用试验结果对模型进行验证分析,结果表明有限元方法可以准确地模拟出节点受力及变形,同时可以方便地得到节点整个破坏过程。螺栓受力分析表明,螺栓剪力越大则其极限抗拉承载力越小。对节点进行不同荷载组合的参数分析的结果表明:节点的临界温度随着拉力或剪力的增加而降低,且剪力的影响更为显著;在所研究的参数范围内,抗拉与抗剪相关承载力基本呈负的线性关系;增加端板厚度可以有效提高节点抗拉及抗剪承载力。

Flush endplate connections are mainly loaded by shear forces at ambient, while in fire large deformation of the beam leads to a huge catenary force within it, and connections are generally loaded to failure by combinations of tension and shear forces. A three-dimensional solid model for flush endplate connections was established by general-purpose finite element program ABAQUS. In this model, the material nonlinearity and deterioration with temperature, and large deformations were taken into consideration. The contact between the various components was explicitly modeled. The results obtained from the analysis showed a good agreement with the experimental responses. By employing the simulation model, the development of bolts section forces was obtained, and it clearly shows that the bolt shear force has negative effects on its tensile capacity. Parametric study was performed under an extensive range of load combinations of tension and shear in fire using the finite element model. The analysis results indicate that the increase of either tension or shear will reduce the failure temperature of the connection. At one specific temperature, the tensile resistance reduces linearly with the increase of shear force within the range studied. And the use of a stiff endplate can enhance both the shear and tensile resistance of a connection.