Seismic Analysis Of The Soil-structure System In Marine Soft Soil For Mid-rise And High-rise RC Frames

The seismic response of the mid-rise and high-rise structures on the soft soil in the coastal area is significantly affected by the soil-structure interaction(SSI).The present study on soil-structure interaction on flexible foundations is mainly carried out for the general soft soil.The mechanical properties of marine soft soil are different from those of soft soil.This will result in a change in the structural seismic response considering the effects of SSI on marine soft soil.However,the research on SSI on soft soil in coastal areas is relatively insufficient.This paper describes a new three dimensional Finite Element model utilizing a nonlinear elasto-plastic model for the soil and superstructure for seismic analysis in marine soft soil.Then the ground motion and foundation input motion of the structure are studied based on the numerical model.Furthermore the seismic response of RC frames in marine soft soil is analyzed.The details are as follows.1.The numerical modeling methods and theories are summarized for seismic nonlinear analysis of soil-structure systems on marine soft soil.The nonlinearity of soil materials and superstructures,the boundary of soil,the meshing of the numerical model of foundation soils,the system damping,the contact between the structure foundation with soil and the seismic waves are discussed based on existing research.The nonlinear numerical model of the soil-structure system is established on marine soft soil for the mid-rise and high-rise RC frames.2.The ground motion of marine soft soil is studied based on the numerical model.And then the foundation input motion(FIM)is studied based on numerical models of a 4-storey frame and a 10-storey RC frame.The amplitude and acceleration spectra of FIM in soil-structure system and ground motion are compared to reveal the influence of soil-structure interaction on the mid-rise and high-rise RC frames.3.The floor acceleration and storey drift of the mid-rise and high-rise RC frames are calculated based on the numerical model in marine soft soil.It is studied how the SSI affects the seismic response of superstructure in marine soft soil.The shear reduction method considering the effect of SSI on the superstrcure seismic responses is proposed for the mid-rise and high-rise RC frames in marine soft soil based on the "Code for seismic design of buildings"(GBJ11-10).