Soil-structure Interaction Model And Seismic Response Of Spatial Latticed Structure

The roof structure is chosen as the analysis model in the current seismic researchof the long-span latticed spatial structure and the relevant seismic theory is mature.The real latticed spatial structure includes the roof structure, the supporting structureand the soil medium. The supporting structure in the long-span latticed spatialstructure is the column or the frame. In most cases, the foundation includes theindependent foundation, the strip foundation, the raft foundation and the pilefoundation. When the structure is on the soil medium, the soil medium and thesuperstructure will vibrate simultaneously under the earthquake. At the same time,some of the energy from the vibration of superstructure will be transmitted to thesurrounding soil medium, and then the vibration in the soil medium will acted uponthe superstructure. This phenomenon is called the soil structure interaction under theseismic actions. Compared with the rigid foundation assumption, the effect of the soilstructure interaction under the seismic actions could be categorized as the followingtwo aspects: the change of the dynamic characteristic which including the decrease ofthe frequency and the change of the mode shape, the increase of the damping ratio.This paper, where the reticulated space structure and the sphere shell with supportingstructure is the analysis model, mainly analyze the interactions between the roof, thesupporting structure and the soil medium and the effect of the interaction on theseismic response of the roof. The main research in this paper is as follows:(1) Suitable soil structure interaction model for the latticed spatial structure.Based on the half-space model by Gazatas, a new model, which considers thecrack between the foundation and the soil under strong earthquake, is put forward. Inthe pile group model, the3-D non-coupling model considering vertical soil-pileinteraction is put forward. With one spatial truss as one example, the new shallowfoundation and the pile group model is verified by the comparison between thecoupling model and the un-uncoupling model.(2) The effect of the dynamic characteristics of the ground motion and soilstructure interaction on the seismic response of spatial structure.Based on the shallow foundation model considering the crack between thefoundation and soil, the effect of two factors including the ground motion characterand the soil structure interaction on the seismic response of spatial structure is studied.When the soil structure interaction is considered, the period of the structurewill be increased. The near field ground motion has the characteristic of the velocitypulse with long period and the high frequency in the far field ground motion will befiltered during the propagation, so both kinds of the ground motions have thecharacteristic of the long period. The effect of the two kinds of the ground motions onthe response of the reticulated spatial structure incorporating the soil structureinteraction is studied.(3) Effect of the radiation damping on the seismic response of the reticulatedspatial structure incorporating the soil structure interactionThere are two main effects in the study of the soil structure interaction on theseismic response of the latticed space structure with shallow foundation. One is theelongation of the period of the structure, second is the increase of the overall radiationdamping ratio. In this paper, the increase of the overall radiation damping is mainlybased on the elongation of period of the first mode shape. The effect of the radiationdamping on the seismic response of the roof structure is mainly considered in the soilstructure interaction analysis.(4) Effect of fully coupling soil pile interaction on the seismic response of thespatial truss supported by the column and the parametric analysis by the softwareopensees.In the analysis model, the nonlinear p-y spring is to model the horizontal soil-pileinteraction; the nonlinear t-z spring is to model the vertical soil–pile frictionsinteraction; the nonlinear q-z spring is to model the soil–pile interactions between thesoil and the force at the end of the pile.(5) Effect of the nonlinear soil pile interaction on the seismic response of thelatticed shell by the software SAP2000.In the analysis model, the skeleton curve of the nonlinear spring in the SAP2000is equal to the skeleton curve of the p-y curve, the t-z curve and the q-z curverespectively. The hysteretic models are assumed for the three springs respectively.Based on the above, the3D soil pile interaction on the seismic response ofsingle-layer shell is studied. Some important conclusions are drawn.(6)Simplified pile analysis model in the seismic design of the single-layerlatticed shell.On the basis of the seismic response of the single-layer latticed shellincorporating the3D nonlinear soil-pile interaction, the seismic response of the single –layer latticed shell incorating the nD rigid model, the impedence function model andthe m model are compared. By the comparison, the simplified soil-pile interactionmodel in the seismic response of spatial model is found.