考虑节点刚度的圆钢管混凝土桁架受压腹杆计算长度分析

Analysis of in-plane effective length of compressive braces of CHS-CFCHS joints in truss structures based on joint rigidity

为考虑节点刚度对钢管混凝土桁架中受压腹杆计算长度的影响,对圆钢管混凝土T/Y型节点在平面内弯矩作用下的抗弯刚度进行了数值研究,比较了空钢管节点和内填充混凝土钢管节点的抗弯刚度的差异,建立了钢管混凝土节点的抗弯刚度参数计算公式,给出了考虑节点刚度的受压腹杆的计算长度。研究表明:空钢管节点的弦杆内填充混凝土后,节点的抗弯刚度有明显的提高,节点刚度取决于弦杆的径向刚度和弦杆、腹杆相贯面的表面积;节点刚度随β、τ的增大而提高,随γ、θ的增大而降低;受压钢管腹杆的计算长度沿用《钢结构设计规范》可能偏于保守;对于上、下弦杆均为圆钢管混凝土杆件的桁架,受压腹杆的计算长度可近似的取0.7l。

The effects of various factors on the joint rigidity of concrete-filled circular hollow section（ CFCHS）joints were analyzed and compared with those of circular hollow section（ CHS） joints. To determine the coefficient of the effective length of a compressed brace that is influenced by joint rigidity in a concrete-filled circular steel tube truss,T / Y CHS-CFCHS joint specimens with different geometry parameters under in-plane bending moment were investigated. The formula of the joint rigidity of CHS-CFCHS joints and the coefficient of the effective length of the compressed brace were established based on geometry parameters of the joints. Results show that the joint rigidity of CHS-CFCHS joints increase accordingly compared to CHS joints. Joint rigidity depends on the chord stiffness and brace-to-chord contact area; joint rigidity decreases as the value of γ or θ increases and increases as the value of β orτ increases. The computation length of the compressed brace may be conservative if the computation is performed according to the design code for steel structure; the effective length of the brace can be considered as 0.7l in the CHS-brace to CFCHS-chord truss.