Elastoplastic Seismic Response And Strength Fracture Anaysis Of Space Lattice Structures Under Multi-Support Excitation

In this paper the dynamic behaviors of space lattice structure is thoroughly analyzed based upon elastoplastic time history method. It includes three parts in detail: how to use the elastoplastic time history method under multiple support excitation actually, the differences of the structural behaviors between multiple and simple support excitation, the rules of strength fracture under those two input modes.The Harichandran model is used as the horizontal coherency function. Horizontal acceleration ground motions, being true of the above coherency function, are generated through the WAWS(weighted amplitude wave superposition) method, which is improved through FFT(fast fourier transform) technique by Prof. Ye. Based on the above theory, the parameters are set reasonably in application and a serial calculation measures are taken to improve the precision.The characteristics of the structure under multiple support excitation are drawn through comparing the results of some space lattice structures, such as double layer cylindrical shell with 60m span, double layer cylindrical shell with 120m span and Laoshan bicycle gymnasium for Peking 2008 Olympic games. The example results indicate that: the members near the supports are in danger under multiple support excitation; the abdomen members also should be pay more attention because the distribution of internal force about structure under multiple support excitation becomes more uniform compared with that under simple support excitation.Strength fracture is one of the most important forms of collapse of space lattice structure under strong ground shock. The strength fracture is thoroughly studied under multiple and simple support excitation by considering elastic-plastic. The results of analysis show that the displacements of certain nodes increase very quickly during the structural failure course and then cause the whole structure to collapse in less than a few seconds, and it is the amount of the members which get into plastic and invalidation that causes the double layer reticulated shell to collapse.