Wind-Induced Multiaxial High-Cycle Fatigue Analysis of Welded Spherical Joints of Spatial Grid Structures

Because of the multiaxial high-cycle fatigue characteristics of welded spherical joints under wind load, it is necessary to do some research on the wind-induced multiaxial high-cycle fatigue of the joints in order to ensure the wind safety of spatial grid structure. A multiaxial high-cycle fatigue analysis methodology was proposed. Firstly, the high-cycle fatigue tests of weldments under uniaxial and multiaxial loading were carried out, and obtained the multiaxial high-cycle fatigue damage life model of weldments based on two-parameter critical surface method. Secondly, based on the wind tunnel test data,the wind-induced response of the grid structure was analyzed, meanwhile, the refined finite element model of the welded joints was established by using the substructure analysis method, so as to obtain the stress time-history and equivalent stress time-history of the dangerous points of each welded joint. The rainfall counts were then performed to determine the starting and ending points of each cycle and its original stress time-history, accordingly identify the critical surfaces in each cycle by using the search method. Finally, based on the multiaxial high-cycle fatigue damage life model obtained in the test, and the cumulative fatigue damage values of all the cycles were calculated according to Miner's linear accumulation criterion, on the basis of which the starting life of the joint was predicted when fatigue damage occurred. The wind-induced fatigue analysis was carried out on the joints of the roof grid structure of Wuhan Natatorium at different locations. The results indicated that the fatigue damage starting life of the windward joints, leeward joints and intermediate joints was far less than the service life of the structure. Therefore, wind-induced fatigue damage might occur on the welded joints within the service life of structure, which should be concerned in the engineering field.