| The study of soil-structure interaction is of great significance for the seismic analysis and design of civil engineering structures.The same structure,built on different sites,may respond differently to earthquake excitation.On the one hand,the presence of site soil magnifies the motion of bedrock.On the other hand,it filters the seismic waves at certain frequencies,and also changes the structure's natural frequency.Whether these changes are beneficial to the seismic performance of the structure requires detailed studies.The traditional rigid foundation assumption is basically reasonable for low-minor and secondary small structures,but it is no longer applicable to large-scale and complex structures such as high-rise buildings,long-span bridges,nuclear power plants and hydraulic engineering.Dynamic analysis methods that consider the soil-structure interaction generally include lumped parameter method,global analysis method,and substructure method.The substructure method is widely used and studied by scholars because of its great advantages in reducing the degree of freedom and saving computational costs.Using the idea of substructure method,this research group proposes a coupling algorithm that considers soil-structure interaction,transforms the dynamic impedance function in frequency-domain into time-domain representation,and introduces it into the time-history analysis framework of the structure.While reducing the great computational costs which global finite element method brings about,it not only considers the influence of foundation and soil properties on the superstructure,but also reflects the nonlinear behavior of the superstructure.Based on the coupling algorithm,this paper analyzes the seismic response of an actual 32-story steel frame-concrete core high-rise building,and studies the influence of soil-structure interaction on the structure from the perspective of basic movement.The analysis results show that the dynamic analysis of large-scale and complex structures considering only the input of free-field motion is not complete,but the basic translation and rotation should be considered,especially the basic rotation caused by the earthquake,and it needs to cause engineers' attention.The weaker the soil,the more rotation of the foundation that cannot be ignored.On the other hand,when using the substructure method to analyze soil-structure systems,the solution of dynamic impedance functions is one of the important steps of the method,so it is crucial to provide a clear and practical method for calculating the dynamic impedance functions of foundations for practical engineering.As the most widely used numerical method for engineering applications,finite element method should be able to be used alone to solve dynamic impedance functions of foundations.This paper proposes to use finite element method combined with artificial boundary method to solve the finite element model in which the rigid foundation is directly exposed to the unitary harmonic load of different frequencies to obtain the basic rigid body displacement of the corresponding frequency,and then to fit the amplitude and phase angle of the steady state displacement.This paper uses the proposed method to calculate the dynamic impedance functions of cuboid rigid foundation and compare the results with literatures.The results show that the real part of the dynamic impedance functions agrees well with the stiffness term(the maximum error is only 5.4%),and because the damping assumptions for the soil are different,the imaginary part,or the damping term is slightly different(the maximum error is 10.0%).This study may provide a reference about the solution of dynamic impedance functions for engineering. |
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