Study On Elastic Vibration Of Space Structures Under Non-uniform Excitations

The influence of spatial variation of seismic ground motion can't be neglected for space structures. It's a task being resolved necessarily how to calculate the seismic response of the structure. This article mainly focuses on the time history analysis of some practical space structures under non-uniform excitation. The compare analysis of the structure response is studied generally under multiple support excitation and simple support excitation from four aspects and some important conclusions are gained.The Harichandran model is used as the horizontal coherency function and Dr. Liu's model is used as the vertical coherency function. Horizontal and vertical acceleration ground motions, being true of the above coherency functions, are generated through the WAWS method, which is improved through FFT technique by Prof. Ye. Based on the above theory, the parameter is set reasonably in application and a serial calculation measures are taken to improve the precision. The seismic response analysis of space structure are studied through the non-uniform time history method including 10 apparent velocity vapp=50m/s, 100m/s……500m/s.Beijing AMECO hangar(space truss), cover sail of palaestra(reticulated shell) located in Harbin Institute of Technology and semi-cylindrical shell are analyzed under both non-uniform excitation and simple support excitation. The number and distribution of frame with greatly different force and the relation to the apparent velocity are studied. It shows that the influence of presdo-static displacement on the frames force near the base is great. Wave-passage effect is decreased with the increase of the apparent velocity. Incoherent effect is irrelative to the apparent velocity. And the safety is insure within the specific span while non-uniform excitation is substituted by simple support excitation.The analysis of the space cable structure of Reilei stadium and Atlanta stadium is same to that of the space lattice structure. It shows that the influence of presdo-static displacement is weak and the cable with the great increase of force is located in the middle of the structure span, because the cable is flexible. The rule of wave-passage effect and incoherent effect is same to that of shell(truss) structure. Non-uniform excitation can be substituted by the simple support excitation within the specific span.Structure response under multiple support excitation which include spatial variety and wave-passage excitation and that including wave-passage effect only are compared. The totally patterns of structure response under two method are similar, but there is a great difference in the number of dangerous frames. On the other hand, the calculation time is comparative. So the complete multiple support excitation is advocated in order to ensure the structure safety.