Finite Element Analysis And Experimental Study On The Load-Carrying Capacity Of Welded Hollow Spherical Joints

Welded hollow spherical joints have been extensively used as a node pattern in spatial structures in recent years. Chinese National Swimming Center 'Water Cube' built for 2008 Olympic Games has adopted large quantities of such welded hollow spherical joints. Although these joints have been extensively investigated, more researches should be conducted in order to solve some existing problems.On the basis of past work, this paper further investigated the factors that may influence the load-carrying capacity of welded hollow spherical joints subject to planar bi-directional forces, especially of welded hollow spherical joints with large diameters and stiffening ribs. A improved formula to calculate the load-carrying force was raised by the analysis of a lot of different joints.Current investigations are carried out on welded hollow spherical joints subject to bi-directional forces, with the determination of failing load according to planar bi-directional forces. However, in practical projects, joints are usually subject to multi-directional forces. By investigating the load-carrying capacity of welded hollow spherical joints subject to planar bi-directional forces, a method considering reduction coefficient on the basis of formula calculating the planar bi-directional load-carrying force and bending moments has been raised, with the specific expression of reduction coefficient given.In practical projects, stiffening ribs are usually used in welded hollow spherical joints with a diameter pf larger than 300mm. However, for joints subject to combined loading of bending moments, no research on the effect of stiffening ribs on load-carrying capacity of joints has been carried out. In this paper, the influence of stiffening ribs on the load-carrying capacity of welded hollow spherical joints subject to combined loading of axial forces and bending moments were researched, corresponding suggestions on their design were given.This paper carried out the measurement of load-carrying capacity on 28 welded hollow spherical joints (including welded hollow spherical with circular steel tubes and welded hollow spherical joints connected with square and rectangular steel tubes) used in the Chinese National Swimming Center 'Water Cube'. Two different load-carrying conditions are used in the experients including axial compression and bending moments and combined loading of the two kinds. For thewelded hollow spherical joints which subject to bending moments and combined loading of the two kinds, the influence of additional eccentricity was investigated by nonlinear finite element analysis, conclusions and some suggestions are given which can be directly applied to 'Water Cube'.