Experimental Studies on Axial Compression Capacity of CHS T-Joints Reinforced with External Stiffeners Under Load

In this paper, the bearing capacity of joints under pre-loading of 3 groups of T-shaped joints reinforced with external stiffeners was investigated. According to the ratio of the diameter of the brace and the chord, it was divided into three groups (β=0.25、0.50 and 0.73) for comparison. The specimen dimension design, the loading process of the pre-loading, the loading system, the welding work during the loading process and the failure mode were introduced in detail. There were two typical failure modes: node failure and out-of-plane tilt. The experimental results showed that when β=0.25, the failure mode of the joint was the yield of the stiffener, and when β=0.5 or 0.73, the joint appeared out-of-plane inclination in different degrees. Therefore, the out-of-plane tilt was the most important failure mode for T-joints under axial load. The welding reinforcement sequence had an important influence on the temperature-induced deformation development of T-shaped circular steel tubes under load. The vertical displacement of the brace increased and the force of the jack decreased when the welding heat was applied, and the vertical displacement of the brace rebounded after the welding cooling, and the force of the jack load sensor increased. The influence of initial load on the bearing capacity of joint was different with different factors. When β=0.25, with the increase of the initial load, the ultimate bearing capacity came later and the total displacement of the structure increased, but the magnitude of the bearing capacity did not change obviously from 250.7 kN to 250.9 kN. When β=0.5, with the increase of initial load, the carrying capacity decreased by 73% from 350 kN to 324.6 kN and joint stiffness also decreased. When the value was 0.73, due to the large out-plane inclination of T3-60, the experiment was stopped ahead of time, but it could be seen that with the increase of the initial load, the ultimate bearing capacity increased by 13.3% from 499.7 kN to 566.2 kN, and the stiffness of the joint did not change obviously.