Study On Influence Of Ground Motion On Soft Soil Seismic Displacement Based On OpenSees

Soft soil subsidence is a phenomenon in which soft soil is softened by earthquake to cause ground or foundation subsidence,and it is one of the main ground damages in soft soil areas.China's soft soil is widely distributed,especially in the economically developed coastal areas.A large number of buildings are built on soft foundations,posing a potential earthquake hazard to the area.Therefore,the research on soft soil seismic subsidence not only has certain scientific research significance,but also has high engineering practical value and social significance.Based on the numerical simulation research method of OpenSees,the free space calculation model of 2D and 3D soft soil foundation is established respectively.The influence of ground motion amplitude,spectrum characteristics and ground motion input on the soft soil subsidence is studied.The seismic response of soft soil foundation under different ground motion conditions is compared,and the influence of two-dimensional model and three-dimensional model on the calculation results is compared.The main results are as follows:1?This paper summarizes the damage caused by soft soil subsidence to the project.The research status of soft soil subsidence is reviewed from the evaluation and discrimination of soft soil subsidence,mechanism,influencing factors and calculation methods.2?The basic situation of OpenSees finite element software is briefly introduced.The material constitutive relation(PIMY constitutive model),soil unit(FourNodeQuad up unit,Brick up unit)and boundary condition(qual DOF)used in this paper are introduced in detail.,laid the foundation for the follow-up work.3?The appropriate model size,mesh element size,boundary constraint condition,soil element material,constitutive model and static loading method are selected to establish a high-efficiency and stable numerical calculation model for 2D and 3D soft soil sites.By changing the peak acceleration of ground motion,spectral characteristics and input mode,the seismic subsidence of the two-dimensional and three-dimensional soft soil foundation models under the above different influencing factors is analyzed,and the influence of ground motion parameters on soft soil subsidence is studied.The results show that the seismic subsidence is affected by the amplitude of ground motion.The larger the PGA is,the larger the seismic subsidence is.The low frequency component of ground motion plays a decisive role in the soft soil subsidence.The calculation result of horizontal + vertical input ground motion is the closest to the actual Happening.4?The numerical calculation results of two-dimensional and three-dimensional models are analyzed from the ground motion peak,spectrum characteristics and input direction.The rationality of the two calculation methods is discussed.The results show that the 3D model calculates the seismic subsidence result larger than the 2D model calculation result and has certain rationality.However,the 3D model has a long calculation time and requires high performance for computer performance,which is not as efficient as the 2D model.Finally,this paper summarizes the main research work and prospects for future research work.