| Under the action of earthquake,the existence of large underground space structure can significantly affect the ground motion of adjacent sites and thus affect the seismic response of adjacent buildings.The present seismic design code usually ignores the influence of underground structure,which makes the superstructure design of adjacent underground structure unsafe.Therefore,shaking table test and theoretical analysis are used in this paper,the influence of underground structure on adjacent ground motion and seismic response of the superstructure was studied,this paper discusses the interaction mechanism between underground structure,soil and superstructure,and establish the correction coefficient of ground motion based on rigid foundation assumption thus the seismic response of structure is more reasonable.The main research contents and achievements of this paper are as follows:1.Shaking table test of underground structure-soil-superstructure interactionIn order to study the interaction of underground structure-soil-superstructure,shaking table tests of soil-underground structure interaction(SUSI),underground structure-soil-superstructure interaction(SSSI)and soil-superstructure interaction(SSI)were designed and carried out.The influence of underground structure on ground motion,dynamic characteristics and seismic response of the superstructure is analyzed.(1)The amplification factor of horizontal acceleration of ground surface is symmetrically distributed along the axis of the underground structure.The horizontal acceleration of ground surface above and adjacent to underground structures is significantly affected.Vertical vibration will occur even under horizontal seismic excitations.The amplification factor of vertical acceleration of ground surface distributed as M-shaped.The influence range of underground space structure can reach the distance equal to its own width on both sides.The amplification factor of acceleration of ground surface is obviously affected by the predominant frequency of input seismic waves,and the amplification factor of acceleration of ground surface decreases with the increase of peak acceleration,but the space amplification factor increases with the increase of peak acceleration.The peak frequency of ground acceleration Fourier spectrum is influenced by the predominant frequency of seismic waves,natural frequencies in horizontal and vertical direction of soil site.(2)When the predominant frequency of the input seismic wave is closer to the fundamental frequency of the superstructure and the peak acceleration is greater,the fundamental frequency of the superstructure decreases more.The soil stiffness degradation of SSSI system is more obvious than that of SSI system under strong earthquake,and the structural frequency decreases faster.The damping ratio first increases and then decreases with the increase of peak acceleration.The damping of soil structure interaction system is non proportional.The real part and imaginary part of the translational vibration mode of the structure increase with the increase of the peak acceleration,and the phase difference between each degree of freedom increases.The rotation of box foundation is more obvious under strong earthquake.The box foundation angle of SSSI system is larger than that of SSI system.(3)The underground structure enhances the motion interaction,which leads to the rocking motion of SSSI system being larger than that of SSI system.The peak values of translational acceleration,rocking acceleration and structural deformation acceleration of SSSI system are not synchronous.The maximum deformation response of SSSI system is 1.267 times of that of SSI system.2.Equivalent linearization calculation method of underground structure site and optimization of Rayleigh damping coefficient(1)The two-dimensional equivalent linearization of soil-underground structure model of the ground acceleration response time history and Fourier spectrum in good agreement with test results,the horizontal peak acceleration error is less than 10%on average.For the underground structure-soil-superstructure model,the average error of peak acceleration of superstructure is less than 35%.The results show that two-dimensional equivalent linearization can be used to analyze the seismic response of underground structures.(2)A simplified equivalent linearization method of soil-underground structure site model is proposed for the underground structure site in horizontal layered soil layer.In this method,the site is divided into near-field region and far-field region.Two-dimensional equivalent linear calculation is used for near-field soil,while linear calculation is performed for far-field soil based on one-dimensional equivalent linearization results.Numerical calculation results show that,compared with the overall model all to do the calculation of two-dimensional equivalent linearization,the error of simplified equivalent linearization method is less than 2%,when the near-field area is within 2 times the width of underground structure,which gives consideration to both calculation efficiency and calculation accuracy.(3)In order to make the frequency independent hysteresis damping in site seismic response analysis equivalent to the viscous damping for time domain analysis,an optimization method is proposed to optimize the conversion frequency of hysteresis damping,on this basis,the optimization method of equivalent Rayleigh damping calculation is constructed.Firstly,the objective function is constructed by minimizing the cumulative acceleration error of the equivalent viscous damping system of the single degree of freedom hysteretic damping system,and the optimization algorithm of the hysteretic damping conversion frequency is established.Then,taking 21 seismic waves as input,the effects of natural frequency,hysteresis damping ratio and dominant frequency on the hysteresis damping conversion frequency are analyzed statistically.The results show that the optimal conversion frequency of hysteretic damping is mainly affected by natural frequency,while the influence of hysteretic damping ratio and dominant frequency is very small.On this basis,taking the minimum ground acceleration response error as the objective function,the constrained optimization equation for solving Rayleigh damping coefficient is established.3.Study on the influence range and degree of underground structure on ground motion and equivalent seismic input(1)In order to analyze the influence range of the underground structure on the seismic response of the site,the variation law of ground motion of the underground structure was studied under the harmonic load and seismic wave input respectively.The numerical results show that the underground structure significantly changes the spatial amplification coefficient of surface.The influence range of linear seismic response under harmonic load and equivalent linearization under seismic action is basically the same.The influence of underground structure on horizontal acceleration response is mainly within the width of 1.5 times from the center of underground structure.The vertical acceleration is mainly within the width of one time from the center of the underground structure.(2)A linear relationship between horizontal acceleration amplification coefficient and ground frequency was established,and a correction coefficient considering the amplification effect of underground structure on ground motion was proposed,which improved the seismic safety of building structures adjacent to underground structure in the site. |
