Sites Velocity Structure Modeling And Seismic Response Analysis In Urban Area

The study of regional seismic effect is of great significance for the evaluation of urban building earthquake damage simulations and the earthquake disaster prevention planning.At present,compared with the structural response,it is still rough to consider the input of ground motion in the regional building earthquake damage simulation,especially the seismic impact of the engineering site.The loose underground sedimentary structure of an urban area and its interaction with the building might have a significant impact on the ground motion.Constructing a fine structural model of the site near the surface and fully considering the seismic impacts of the engineering site can represents the regional building earthquake damage more accurately.Unlike the deep crustal structure that can be approximated as a layered structure,a complex interactive deposition phenomenon exists in the loose rock and soil body within tens to hundreds of meters near the surface,This greatly changes the local structure of the shallow engineering site,making it difficult to construct the dynamic model and complicates the seismic effect.As a recommended method for seismic micro-zoning and seismic safety assessment,the equivalent linearization method has been widely used in the analysis of the seismic response of the soil layer in a single site,However,it is not enough in the simulation of regional multi-dimensional site response.Therefore,the present study takes the Harbin urban engineering site as an example and carries out the following research work in terms of the construction of a fine urban shallow surface interactive sedimentary site model.It further analyzes the regional site seismic response based on the equivalent linearization method:1.Aiming at the urban sites with staggered and complex deposition,based on prior geological information,a modeling idea is proposed to define the modeling boundary of staggered soil structure.The idea is to separate the soil structure with a simple distribution and then solve the specific spatial probability distribution of various staggered soil structures with a sequential indication simulation method.Based on the collected and analyzed borehole data,the 3D engineering geological model of the Harbin urban site is established.The comparison with the borehole data and geological structure shows that the 3D geological model has certain space predictability.2.A wave velocity structure model based on a complex site engineering geological model is developed to establish the 3D velocity structure model of the Harbin urban site.The model is developed with the help of a sequential Gaussian simulation method combined with the spatial correlation between shear wave velocity and engineering geological structure.The reliability of the method is verified by a comparative qualitative analysis with a geological section.In addition,a quantitative comparison with the statistical relation between shear wave velocity and buried depth and measured wave velocity is also conducted.The present model is more convenient to set the nonlinear dynamic parameters according to the detailed geotechnical types in the equivalent linearization analysis of seismic response.3.Based on the idea of replacing the iterative calculation of the maximum shear strain amplitude with the shear strain amplitude,the equivalent linearization method of seismic response of the regional site is realized by using Open Sees by analyzing of the 1D ideal model and the 3D structural model of the Harbin urban site.The inspection of method feasibility and accuracy is conducted by analyzing the 1D ideal model and the 3D structure model of the Harbin urban site;the feasibility and accuracy of the method are tested.