负载下T形圆钢管外加劲肋加强节点轴向受压承载性能试验研究

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

为研究负载下T形圆钢管外加劲肋加强节点轴向受压承载性能,根据支管与主管的外径之比β不同(分别为0.25、0.50和0.73),分成三组进行对比试验。详细介绍了试件尺寸设计、预应力的加载过程、加载制度、持载过程中的焊接工作、破坏形态等。试验出现两种失效模式:节点破坏和平面外倾斜。试验结果表明:当β=0.25时,负载下节点的破坏模式为加劲肋处节点屈服;当β=0.5或0.73时,节点都出现不同程度上的平面外倾斜;焊接加固顺序对负载下T形圆钢管的温度作用变形发展具有重要影响;焊接热作用时,杆件的竖向位移增大,千斤顶力的作用相对减少;焊接冷却后,杆件的竖向位移出现回弹,千斤顶荷载传感器显示的作用力增加,初始荷载对于节点承载性能的影响随β的不同产生不同的影响,当β=0.25时,随着初始荷载的增大,极限承载力出现滞后,结构总位移加大,但承载力的大小没有明显的变化,从250.7 kN提升为250.9 kN;当β=0.5时,随着初始荷载的增大,极限承载力从350.3 kN降低到324.6 kN,降低了7.3%,节点刚度变小;当β=0.73时,由于T3-60的平面外倾斜过大,试验提前停止,但可以看出,随着初始荷载的增大,极限承载力从499.7 kN增大到566.2 kN,增大了13.3%,节点刚度无明显变化。

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 whenβ=0.25,the failure mode of the joint was the yield of the stiffener,and whenβ=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.Whenβ=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.Whenβ=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.