方钢管焊接空心球节点的承载力与实用计算方法研究

国家游泳中心“水立方”采用了一种新型的多面体空间刚架结构,杆件形式包括圆钢管、方钢管和矩形钢管,节点则主要采用焊接空心球节点。本文系统研究在轴力、弯矩及两者共同作用下方钢管焊接空心球节点的受力性能与承载能力。建立了采用理想弹塑性应力-应变关系、Mises屈服准则,同时考虑几何非线性的有限元分析模型,并对承受轴力、弯矩及两者共同作用的方钢管焊接球节点进行了大量的有限元参数分析。对轴力和弯矩共同作用的焊接球节点,其轴力-弯矩相关关系与节点的几何参数(包括空心球的球径、壁厚及钢管边长)无关。对若干典型节点进行了试验研究,直观了解节点的受力性能和破坏机理,并验证了有限元模型的正确性。还推导了基于冲切面剪应力破坏模型的节点承载力简化理论解,从而得到节点承载力计算公式的基本形式。最后,综合简化理论解、有限元分析和试验研究的结果,建立了轴力、弯矩及两者共同作用下方钢管焊接球节点承载力的实用计算公式,其中,对轴力和弯矩共同作

Load-carrying capacity and practical calculation method of welded hollow spherical joints connected with square steel tubes

New polyhedron space frame structure is adopted in the National Swimming Center "Water Cube".Circular hollow sections,square hollow sections and rectangular hollow sections are employed as structural members,while welded hollow spherical joints are employed to connect the members.This paper investigates the structural behavior and load-carrying capacity of welded hollow spherical joints connected with square steel tubes and subjected to axial forces, bending moments and combined loading of the two.Based on the elastic-perfectly plastic model and the Mises yield criterion,a finite element model for the analysis of these joints is established,in which the effect of geometric nonlinearity is taken into account.A major parametric study was then carried out employing this model.It is shown that when the welded spherical joint is subjected to combined axial forces and bending moments,the axial force-bending moment correlation is independent from their geometric parameters,such as the diameter and the wall thickness of the spherical joint,and the side length of the steel tube.Experiments on four typical full-scale joints were conducted to understand directly the structural behavior and the collapse mechanism of the joint,and also to validate the finite element model.A simplified theoretical solution is also derived for the loading-carrying capacity of the joint based on the punching shear failure model,and the basic form for the design equation is obtained.Finally,by utilizing the results from the simplified theoretical solution,finite element analysis and experimental study,