| For the high-rise building built on medium soft soil foundation or soft soil foundation,the interaction between soil and high-rise building is very complicated under the action of the dynamic load.Especially under the action of the near-fault earthquake,it will have a huge impact on the high-rise building.As the key of the soil-structure dynamic interaction（SSDI）,there is few studies on the accurate and practical calculation method for the foundation dynamic impedance by the test.The near-fault ground motion has obvious impulse effect,which can cause great damage to the high-rise building.However,there is a lack of researches on the simulation of spontaneous rupture process of the near-fault earthquake.Therefore,this paper takes the high-rise building as the research object,systematically studies the dynamic response and the foundation impedance calculation method of the SSDI system under the different loads,simulates the spontaneous rupture process of the near-fault earthquake,and explores the influence of the pulse-type ground motion on the dynamic response of the SSDI system.The main innovative work and research results are as follows:（1）The study on the influence laws of the dynamic response and the foundation impedance of the SSDI system under the harmonic load is carried out.Based on the shaking table model test of the structure-foundation dynamic interaction（SFDI）system,the numerical analysis method of the SSDI system is established and verified.By adjusting the test design parameters,the analysis models of the SSDI system are established.By conducting the steady-state excitation vibration analysis of the SSDI system,the frequency response function of the SSDI system is obtained,with which the frequency response characteristics are analyzed.Then the influence of the model parameters on the frequency response function and dynamic response of the SSDI system are studied.Using the traditional calculation method of the foundation dynamic impedance under the steady-state excitation,the value of the foundation dynamic impedance is calculated,and the influence of the model parameters on the foundation impedance is studied.Then,the calculated value of the foundation dynamic impedance is compared with the theoretical value of the same analysis model based on the elastic half-space theory.The results show that the established numerical analysis method is reliable and reasonable,and the established analysis models can be used to investigate the dynamic response and the foundation impedance of the SSDI system.Under the same excitation force,the structure response under the top excitation is larger than that under the bottom excitation.The change law of foundation rotational stiffness coefficient kmm with model parameters is different from other foundation impedance coefficients.For the same analysis model,the calculated value of the foundation dynamic impedance is basically consistent with the theoretical value based on the elastic half-space theory,but there is still a certain error,which indicates that the traditional calculation method of the foundation dynamic impedance under the steady-state excitation is insufficient.（2）The field vibration test of the SSDI system under the impact load is carried out.The frequency response function of the SSDI system was obtained by the field vibration test,and the frequency response characteristics are analyzed.Based on the previous research,the frequency-domain formula of the total displacement of the superstructure considering the influence of the foundation motion under the impact load is derived.With the frequency response function and the total displacement formula,the estimated values of the natural frequency and modal damping ratio of the fixed foundation of the superstructure are obtained,and the contribution of the foundation motion to the total motion of the top of the structure and the vector representation of the total motion of the top of the structure are quantitatively analyzed.The conditions that need to be met to ignore the rigid-body motion of the foundation and the change caused by the rigid-body motion of the foundation at the fixed-base resonance frequency are studied.Then the accurate and practical calculation method for the foundation dynamic impedance under the impact load is proposed.The test value of the foundation dynamic impedance under the impact load is obtained by the frequency response function,which is compared with the theoretical value based on the response theory.The results show that for vibration of N-S direction,the fixed-base resonance frequencies and modal damping ratios of the superstructure obtained by the test are 21.97%and-30.37%higher than the corresponding values of the SSDI system.At the natural frequency of the SSDI system,the total roof displacement of the top of structure is all almost caused by the foundation motion.The test value of the foundation dynamic impedance is in good agreement with the theoretical value based on the response theory.The proposed method can accurately calculate the foundation dynamic impedance and have higher validity.（3）The study on the influence laws of the dynamic response and the foundation impedance of the SSDI system under the seismic load is carried out.Based on the analysis models of the SSDI system,the transient ground motion analysis of the SSDI system is conducted.The internal relation of the dynamic response of the SSDI system and the influence of the model parameters on the dynamic response of the SSDI system under the seismic load are studied,and the change laws are revealed while the reasons are analyzed.The value of the foundation dynamic impedance under the seismic load is calculated by the calculation method of the foundation dynamic impedance under the impact load,which is compared with the foundation impedance of the same analysis model based on the elastic half-space theory.The results show that the distribution of the peak contact pressure is closely related to the amplitude and spectrum characteristics of the input ground motion.The influence of the interaction effect on the seismic response of the foundation base is mainly reflected in the maximum frequency component difference between the top center point A1 of the foundation and the surface node S10 of the soil near the natural frequency of the input ground motion.The degree of the influence of the interaction effect on the dynamic response of the SSDI system depends on the relative stiffness of the structure and the foundation soil.For the same analysis model,the calculated value of the foundation dynamic impedance under the seismic load is much consistent with the theoretical value based on the elastic half-space theory,which indicates that the calculation method of the foundation dynamic impedance under the impact load can accurately calculate the foundation dynamic impedance under the seismic load.The method is more effective than the traditional structure steady-state excitation method.（4）The study on the dynamic response and the foundation impedance of the SSDI system under the pulse-type seismic load is carried out.Based on the secondary development of the VFRIC user subroutine and the sub-model technology,the numerical analysis method to simulating the near-fault spontaneous rupture process is established and verified,with which the physical nature of the near-fault spontaneous rupture is revealed,then the influence of the near-fault pulse-type ground motion on the dynamic response of the SSDI system is studied,which is compared with the far-fault ground motion.The foundation dynamic impedance under the pulse-type seismic load is calculated by the calculation method of the foundation dynamic impedance under the impact load,which is compared with the calculated value of the foundation impedance of the same analysis model under the seismic load.The results show that the established numerical analysis method can accurately simulate the spontaneous rupture process of near-fault.The vertical component of the near-fault ground motion is relatively large,and the ratio between the peak vertical acceleration and the peak horizontal acceleration is 1.531,which exceeds the commonly used ratio of 2/3 at present.Compared with the far-fault ground motion,the near-fault ground motion can cause greater damage to the structure.For the same analysis model,the calculated value of the foundation dynamic impedance under the pulse-type seismic load has a small difference from that under the seismic load,which indicates that the calculation method of the foundation dynamic impedance under the impact load can accurately calculate the foundation dynamic impedance under the pulse-type seismic load.The calculation of the foundation dynamic impedance has nothing to do with the type of load applied on the structure. |
