Dynamic Response Of Space Lattice Structure With Lower Framework Adopting Multi-support Seismic Input

It is one of the most important work to make certain the seismic input when analysizing the aseismatic problems about large span spatial structure. Obviously, it is unreasonable that adopting the coherent-vibration input method to simulate the actual seism to large span spatial structure. So more and more engineers adopt multi-support input method to the aseismic design of the large span spatial structure instead of coherent-vibration input method. The object of study of this paper is two-layer ellipse lattice shell with long axis 120m and short axis 90m ,which is supported by two-layer concrete frame. This paper only considers phasic difference and adopts south and north component and vertical component of EI-Centuro(1940). The seismic wave propagation is always same to the long axis of the superstructure. The dynamic behaviors of the model are analyzed based upon time history method under simple support excitation and two apparent velocity V_app=500m/s,1000m/s under multiple support excitation. The coherent-vibration input equals to the apparent velocity V_app=∞in this paper. Model is founded by ANSYS soft ware. Seismic input programs are compiled by Ansys Parameter Design Language. Choosing 7 nodes and 7 cells of upside structure , 5 nodes and 5cells of underside structure to compare the differences under coherent-vibration input and multi-support seismic input respectively. Analysis of mode indicates: the vibration mode of the model is mainly vertical and the effect of retortion is little. The paper also investigates the seismic apparent velocity effect on the seismic responses of the structure. The results show that when the horizontal seismic wave vibration and propagation directions are same to each other, the seismic responses of the upside of the structure are amplified under multi-support input. And when the two directions are vertical to each other,the responses are reduced under multi-support input. Moreover,when the seismic wave vibration directions is vertical,the seismic responses are indefinitely by the apparent velocity effect. In any case, the seismic responses of the underside of the structure under multi-support input are more amplified greatly than coherent-vibration input,and the bigger apparent velocity becomes , the more obvious the trend becomes. So the multi-support input method is suggested to consider in such kind of structures .