钢管混凝土K形节点应力集中系数计算方法

Calculation method of stress concentration factor for CFST K-joint

以钢管混凝土K形(CFST-K)节点为研究对象,进行了7个CFST-K形节点和1个钢管K形(ST-K)节点足尺模型试验和实体有限元分析;分析了现有CFST-K形节点应力集中系数的适用性;基于管内混凝土约束作用对CFST-K形节点变形形态的影响,提出了CFST-K形节点应力集中系数的缓解系数,并采用理论分析方法推导得到考虑管内混凝土约束作用的CFST-K形节点应力集中系数计算方法。结果表明:CFST-K形节点的最大应力集中系数均出现在受拉支管与主管相贯焊缝靠近主管侧冠点位置;CFST-K形节点应力集中系数与壁厚比呈正相关关系,而径厚比与管径比对CFST-K形节点应力集中系数影响较小;CFST-K形和ST-K形节点最大应力集中系数分别为3.98和6.08,管内混凝土能使CFST-K形节点应力集中系数下降约34.5%。现有CFST-K形和ST-K形节点应力集中系数计算方法未能充分考虑管内混凝土约束作用对CFST-K形节点应力集中系数的影响,且未考虑几何参数之间的耦合关系,采用其进行CFST-K形节点应力集中系数计算时精度较低;所提出的考虑管内混凝土约束作用的CFST-K形节点应力集中系数计算方法可将计算误差由现有计算方法的58.0%降低至19.6%。

With the concrete filled steel tube K-shaped(CFST-K) joint taken as the research object, full-scale model tests and solid finite element analysis on seven CFST-K joints and one steel tube K-shaped(ST-K) joint were carried out. The applicability of existing stress concentration factors(SCF) of CFST-K joints was analyzed. Based on the effect of concrete constraint in tube on the deformation morphology of CFST-K joints, the relief coefficient of SCF for CFST-K joint was proposed, and the calculation method of SCF of CFST-K joints considering concrete constraint in tube was derived by theoretical analysis. The results show that the maximum SCFs of CFST-K joints all appear in the position of the intersecting weld between branch tube in tension and main tube near the crown point of main tube. The SCF of CFST-K joints is positively correlated with the wall thickness ratio, while the diameter-thickness ratio and tube diameter ratio have little influence on the SCF of CFST-K joints. The maximum SCFs of CFST-K and ST-K joints are 3.98 and 6.08, respectively, and the concrete in tube can reduce the SCF of CFST-K joints by about 34.5%. The existing calculation methods for the SCF of CFST-K and ST-K joints fail to fully consider the influence of concrete constraint in tube on the SCF of CFST-K joints, and fail to consider the coupling relationship between geometric parameters, so the accuracies of the SCF of CFST-K joints calculated by these methods are generally low. With the proposed method, the calculation error of the SCF of CFST-K joint can be reduced from 58.0% to 19.6%.