钢管混凝土桁架Y型管节点热点应力研究

为研究主管支撑条件及支管与主管夹角对钢管混凝土桁架(CFST)Y型管节点热点应力分布的影响,利用ANSYS采用20节点实体单元,考虑相贯线焊缝建立Y型管节点空间有限元模型,计算分析在一端固定,一端铰接、两端固定、两端铰接3种边界条件下,支管不同角度变化时(20°, 40°, 60°, 80°, 90°),支管轴压作用下主管和支管焊趾处,热点应力集中系数沿相贯线焊缝分布情况。有限元分析结果与已有试验结果进行对比,验证模型的可靠性。研究结果表明:相同约束条件下,随支管角度增大,主管和支管沿焊缝的热点应力集中系数表现为增大,主管热点应力集中系数最大值始终发生在冠点,支管热点应力集中系数最大值由冠点向鞍点移动;同一角度时,随着主管两端约束的加强,主,支管热点应力集中系数分布有所减小,主管鞍点附近受约束条件影响很小。由于局部和整体的刚度同时影响SCF,可以考虑改变节点形式或者减少计算长度、加强固端约束达到降低SCF的目的。

Study on Hot-spot Stress of Y-Joints of Concrete-filled Steel Tubular Truss

In order to study the influence of supporting conditions and the angle between branch and chords on the hot-spot stress(HSS) distribution of Y-joints in concrete-filled steel tubular(CFST) truss, ANSYS with solid element of twenty nodes is employed and finite element models of Y-joints of CFST in consideration of weld geometry are built to calculate the distributions of the hot-spot stress concentration factor(HSCF) along the weld toe when the brace is subjected to axial compression under three support conditions of one fixed end and the other pinned, both fixed end, both pinned end with the angle changing from 20° to 90°(20°, 40°, 60°, 80°, 90°)chords. The model is verified reliable by comparing the numerical results with experimental results. Research results show that under the same support condition, the HSCF along the weld toe increases with the increase of angle. The maximum HSCF of chords always takes place at the grown point and the maximum HSCF of braces moves from the grown point to the saddle point. At the same angle, with the enhancement of the boundary restraint, the hot-spot stress concentration factor(HSCF) of either braces or chords decreases to some extent, and HSCF is little affected by restraint conditions in the vicinity of saddles. Since the local stiffness and overall stiffness affect SCF simultaneously, it may be considered to change the joint form or reduce the calculation length and strengthen the end constraint to reduce SCF.