圆端形椭圆钢管T形相贯节点轴压性能试验研究与承载力计算

圆端形椭圆钢管是一种融合圆形和矩形截面特征优势的构件，其圆端部分可以提供良好约束，矩形部分可实现快捷连接，在桁架结构中有着良好的应用前景，然而目前尚缺乏有关圆端形椭圆钢管相贯节点的受力性能研究。为此，通过对13根圆端形椭圆钢管T形相贯节点开展轴压性能试验，研究相贯类型、主支管径比、主支管夹角和是否填充混凝土等对其破坏模式、承载力、初始刚度和延性等力学性能的影响，明确圆端形椭圆钢管T形相贯节点在支管受压作用下相较圆形或矩形钢管相贯节点的承载特征差异，揭示相贯节点的受力机理，提出圆端形椭圆钢管相贯节点的轴压承载力计算式。研究结果表明，圆端形椭圆钢管T形相贯节点表现出良好的轴压性能；支管与主管圆弧段连接的相贯节点轴压承载力分别为圆形或矩形钢管相贯节点的1.07~1.66倍，具有明显的承载优势；主管填充混凝土可使圆端形椭圆钢管T形相贯节点的轴压承载力和初始刚度分别提高75.5%~103.4%和11.9%~60.6%；通过试验结果验证，提出的轴压承载力计算式可较准确地评估圆端形椭圆钢管T形相贯节点的轴压承载力。

Experimental investigation and design of round ended elliptical steel tubular T-joints under axial compression

The round-ended elliptical steel hollow section (REHS) is a novel type of steel tube combining the features of circular and rectangular cross-sections. The circular part could provide excellent confinement, and the rectangular part offers connecting convenience. Hence, the REHS possesses a good prospect of application in truss structures. However, investigations on the behaviour of REHS tubular joints are scarce. Herein, this paper conducted testing of 13 REHS tubular T-joints under axial compression. The influence of various parameters, including the intersecting orientation, chord/brace diameter ratio, concrete infill, and angle between chord and brace, on the failure modes, strength, initial stiffness, and ductility of the axially-loaded REHS tubular T-joint were investigated. The strength feature index of the type of tubular joint was figured out by comparing its axial strength with those of circular hollow section (CHS) and rectangular hollow section (RHS) steel tubular joints. The loading mechanism of the joint node under brace compression was revealed. Finally, a design method for predicting the axial compression strength of the REHS tubular joints was proposed. The results indicated that the REHS tubular exhibited good axial compression behavior. The tubular joints whose brace was welded to the arc segment of the chord possessed superior strength advantage, and their strength was 1.07-1.66 times as compared to those of the CHS or RHS tubular joint. Filling concrete into the chord could highly improve the strength and initial stiffness of the axially-loaded REHS tubular joint, and the improvements were respectively 75.5%-103.4% and 11.9%-60.6%. The design method presented in this paper could assess the axial compression strength of the REHS tubular T- joint accurately via the test validation.