Seismic Response Analysis Of Long-span Grid Structures Under Multi-support And Multi-dimentional Earthquake Excitations

Because of reasonable force，light weight，low cost and flexible stuctural forms，large-span spatial structures has been widely used in large public buildings. However，the natural frequencies of large-span structures are intensive，the vibration modes arecomplex，the spans of the structures are long，they sometimes will lead to greatervibration and generate larger deformation，the structures with large planar size aredifferent from each fulcrum ground motion，the spatial changes of ground motion willhave an important influenc to seismic responses of structures.Therefore，multi-supportexcitation is necessary on study large-span structures seismic response.This article mainly has used time history method to analyze the seismic responseof the long-span grid structures under multi-support and multi-dimentional earthquakeexcitations and under single-support earthquake excitations，the rule of seismic responseof grid structures has been obtained，specific research work are as follows：(1) A long-span grid structure with planar size92m×60m is an example，undermulti-support and consistent input,the seismic responses are analyzed andcompared.The change rule of bar internal force under horizontal and vertical earthquakeare found.The influence factor of the bar internal force change rule are discussed.(2) The responses of the upper space truss structure with the boundary conditionssimulated using fixed hinge support and the overall space truss structure，underunidimensional consistent;two dimensional consistent and the three dimensionalconsistent input，are analyzed with the fluence of each direction earthquake excitationfounded. The different response regular of two grid structures under three dimentionaland multi-support seismic excitation are summarized. Studies have shown that traveling wave effect have an effect on member internalforce of long-span grid structures and the impact is connected with the species ofseismic wave,the value of wave velocity and the number of seismic wavecomponent;The traveling wave effect have different impact on different rack bars ordifferent internal forces.When analysis seismic response of grid structures,separatemodel is suggested to use.When analysis seismic response of long-span grid structures,multi-support and multi-dimentional earthquake excitations is adviced to use.