N形主方支圆钢管间隙节点受力性能研究

Research on Mechanical Properties of CHS-to-SHS Gap N-Joints

为研究N形主方支圆钢管间隙节点的静力性能及其与搭接节点受力性能的关系,对2个N形主方支圆钢管间隙节点和2个对应的搭接节点进行了节点承载力试验研究。试验表明:间隙节点的承载力低于相同管径的搭接节点,4个节点的主管均出现了明显的塑性变形,支管较小的2个节点其支管也发生了局部屈曲,试件破坏时间隙节点的主管壁相对变形比相应的搭接节点要大。以试验为基础,建立了N形主方支圆钢管间隙节点的有限元分析模型,对不同支管直径与主管宽度比、主管宽度与壁厚比、支管与主管的壁厚比、主管轴力及支管间隙的节点进行了有限元分析。研究表明:支管全截面屈服破坏(BMF)、主管壁局部塑性破坏(CP)和支管局部屈曲与主管壁局部塑性破坏的联合破坏(BLB+CP)是N形主方支圆钢管间隙节点的主要破坏模式;支管直径与主管宽度比、主管宽度与壁厚比、支管与主管的壁厚比、主管轴力对N形主方支圆钢管间隙节点承载力的影响与对搭接节点的影响具有类似的规律;支管间隙大小对N形主方支圆钢管间隙节点承载力的影响不容忽视。利用线性回归方法,在GB 50017—2017《钢结构设计标准》现有承载力计算公式基础上,拟合出了考虑相关影响因素的承载力修正计算式。

In order to study the static behavior of CHS-to-SHS gap N-joins and its relations with the behavior of overlap joints, two CHS-to-SHS gap N-joints and two corresponding overlap joints were tested. The test revealed that the bearing capacity of the gap joints was lower than that of the overlap joints with the same diameter of the tubes. Obvious local plasticity failure of the chord occurred in all the four joints, and local buckling also occurred in the two joints with smaller branches. Meanwhile, the relative deformation of the chord wall of the gap joints was larger than that of the corresponding overlap joints at the ultimate state. Based on the experiment, the finite element analysis models of CHS-to-SHS gap N-joints were established, and the finite element analysis of the joints with different brace-to-chord width ratios, chord width-to-thickness ratios, brace-to-chord thickness ratio, axial loads of chord and gap sizes between braces was carried out. The analysis results showed that the main failure modes of the gap joints were the brace member failure(BMF), the chord plasticity failure(CP), and the combined failure of brace local buckling and chord plasticity(BLB+CP). Moreover, the influence of brace-to-chord width ratio, chord width-to-thickness ratio, brace-to-chord thickness ratio and axial force of chord on the bearing capacity of CHS-to-SHS gap N-joints was similar to that of corresponding overlap joints. Furthermore, the effect of gap size between braces on the bearing resistance of CHS-to-SHS gap N-joints could not be neglected. Finally, based on the design equation in the code, a formula for predicting the ultimate bearing capacity of CHS-to-SHS gap N-joints was proposed by applying multivariate regression analysis.