轻质高强方钢管轻骨料混凝土加劲X形节点构造和承载力研究

Research on Structure and Bearing Capacity of Stiffened X-Joints of Lightweight Aggregate Concrete-Filled High-Strength Square Steel Tubes

为研制轻质高强桁架节点构造及其承载力,对Q345B方钢管轻骨料混凝土加劲X形节点和基本型节点进行了静力加载试验,考察了支主管间设置加劲板和支主管内浇灌轻骨料混凝土对节点破坏模式和承载力的影响。试验结果表明:加劲节点的破坏模式有加劲板与剪压支管焊缝开裂、剪压支管翼板被加劲板拉开、剪压支管在靠近加劲板外端截面剪压破坏;基本型节点的破坏模式为支主管焊缝开裂;支主管间设置的加劲板明显推迟了节点的屈服和断裂进程,支主管内浇灌轻骨料混凝土有效防止了方钢管屈曲,显著提高了节点承载力,加劲节点的焊缝开裂荷载和极限承载力较基本型节点分别提高63.3%和18.3%。根据加劲X形节点试验破坏模式,推导了考虑加劲板应力传递和扩散效应的方钢管轻骨料混凝土加劲X形节点的加劲板与剪压支管焊缝开裂、剪压支管翼板拉开、剪压支管剪压破坏的力学计算模型和承载力计算式。建议的加劲X形节点的承载力计算式的计算误差为-27.8%~+3.7%。

In order to study the structure and bearing capacity of lightweight high-strength truss joints,static loading tests were carried out on X-joints with stiffened plates and basic X-joints of lightweight aggregate(LWA)concretefilled Q345B steel square tubes.The effects of the stiffened plates between braces and chords and the LWA concrete poured into braces and chords on the failure mode and bearing capacity of X-joints were studied.Tests results showed that the failure modes of stiffened X-joints were weld cracking between stiffened plates and braces under shear and compression,tension failure of brace flange under shear and compression by stiffened plates,and shear and compression failure at sections of braces under shear and compression near stiffened plate outer edge.The failure mode of the basic X-joints was weld cracking between braces and chords.The yield and fracture process of X-joints were delayed and the bearing capacity of X-joints increased significantly due to the stiffened plates between braces and chords.Pouring LWA concrete into braces and chords could effectively prevent buckling of square steel tubes.The weld cracking load and the bearing capacity of stiffened X-joints were 63.3%and 18.3%,respectively,which were higher than those of the basic X-joints.According to the failure modes of stiffened X-joints,the calculation models were established and the bearing capacity calculation formulas were derived considering the effects of stress transfer and diffusion of stiffened plates for fracture of fillets between stiffened plates and braces under shear and compression,flange pulling of shear-pressure braces,shear-compression failure of shear-pressure braces of stiffened X-joints of lightweight aggregate concrete-filled high-strength square steel tubes.The calculation error of the suggested bearing capacity formula for stiffened X-joints was-27.8%to+3.7%.