采用基于微观断裂机制的空穴扩张模型(VGM)和应力修正应变模型(SMCS)对XK型相贯节点进行断裂预测,分析了有限元模型中考虑焊缝构型与否对断裂预测结果的影响.通过与试验结果的对比,证明了合理考虑焊缝构型在相贯节点断裂预测中的重要性,验证了VGM模型用于预测相贯节点在单调荷载作用下延性断裂的适用性.分析了XK型相贯节点在腹杆轴力作用下的破坏模式和极限承载力.结果表明,XK型相贯节点可能在受拉腹杆与弦杆之间的焊缝处发生断裂,这种破坏模式属于强度破坏,节点极限承载力应取该断裂荷载;XK型相贯节点也可能在受压腹杆与弦杆相交处因过大的塑性变形而破坏,此时,节点极限承载力应取荷载-弦杆变形曲线的峰值荷载.XK型相贯节点的破坏模式与节点几何构造和腹杆受力状态有关.%Micromechanical fracture models,void growth model (VGM) and stress modified critical strain model (SMCS),were adopted in fracture prediction of tubular XK-joints.The influence of welding detail in FE model on fracture prediction was analyzed.Based on comparisons with experimental results,the importance of reasonable modeling of the welding detail was illustrated and the applicability of VGM on fracture prediction of tubular joints was verified.Failure modes and ultimate load bearing capacity of tubular XK-joints under axial loads of brace members were then analyzed.The results showed that the joint may fail by fracture at the weld toe between the brace member in tension and the chord.This failure mode is strength failure and the fracture load should be taken as the ultimate load bearing capacity of the joint.The joint may also fail at the intersection between the brace member in compression and the chord due to excessive plastic deformation,and hence,the peak load on the load-chord deformation curve shall be taken as the ultimate load bearing capacity of the joint.The failure mode of the joint depends on the geometric configuration of the joint and loading conditions of brace members.
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