| With the rapid development of social economy and continuous population expansion,urban construction land is becoming increasingly scarce.The subway is widely welcomed as an efficient and clean means of transportation,and most large and medium-sized cities have subways.Earthquake disaster occur frequently in China.Once subway stations are damaged by earthquakes,it is difficult to estimate the casualties and economic losses.To meet people’s daily travel needs,subway stations are mostly close to densely populated areas such as residential areas and commercial circles,with many existing buildings around them.When an earthquake occurs,the wave field and additional stress field generated by existing building vibrations will cause certain disturbance to the foundation,which will inevitably affect the seismic response of subway stations.Therefore,it is necessary to study the impact of adjacent ground buildings on the seismic response of shallow buried subway stations.In view of this,this article uses numerical simulation as the main research method to analyze the seismic response of shallow buried subway stations affected by adjacent upper frame structures.The research content is as follows:(1)Taking the double layer and three span subway station of Shanghai People’s Square Line 2 as the background,the seismic response was calculated using 3D and 2D plane finite element models,and the rationality of the existing 2D plane strain model was evaluated based on the calculation results of the 3D model.The research results indicate that when using the existing two-dimensional plane model for calculation,the seismic response error of the side wall is within 19.95%,and the seismic response error of the center column is relatively large,with a maximum of 44.60%.The center column error is caused by the discontinuity of the center column along the driving direction.To reduce the seismic response error of the central column,this article improves the existing two-dimensional plane model,and the calculation results show that the improved model can significantly reduce the calculation error of the central column.(2)Exploring the influence of the selection of seismic input interfaces on the seismic response calculation results of subway station structures.When calculating the seismic response of subway stations,there are two options for inputting seismic motion.One is input from the bedrock surface,and the other is input from the interface 70 meters below the ground.This article calculates the seismic response of subway stations under two types of interface inputs,and evaluates the seismic response error of subway station structures under the second interface input based on the calculation results of the first interface(bedrock surface)input.The results show that when the ground motion input surface is 70 m below the ground surface,the seismic response of the subway station structure is greater than that of the real bedrock where the ground motion input surface is located.The error calculated within the elastic range is 16.79%~61.75%,and the error considered when considering the nonlinear situation of the soil is29.19%~61.41%.It is recommended that when conducting seismic response analysis of subway station structures in deep and weak sites,the bedrock surface should be selected as the seismic input surface.(3)Under the assumption of viscous damping,before solving the motion equation of the dynamic system in the time domain,it is necessary to clarify the damping matrix.Usually,the Rayleigh damping model is used,and there is only one damping ratio in the expression of the Rayleigh damping coefficient.However,in the calculation model of the soil structure interaction system of subway stations,there are two materials with different damping ratios: site soil and concrete,and the damping ratios of soil layers at different depths may also be different,At this point,only one equivalent damping ratio can be used to describe the damping of this soil structure system.This paper studies the method for determining the equivalent damping ratio of the damping matrix in the structural motion equation of subway stations.The research results indicate that for the structural system of subway stations,the contribution of various material damping ratios should be considered.Replacing the damping ratio of the system with only one material damping ratio will result in significant errors.In addition,the selection of two frequency values for calculating the Rayleigh damping coefficient was studied.The research results indicate that when the difference between the natural frequency of the structure and the peak frequency of the seismic response spectrum is significant,the calculation error of selecting the fundamental frequency and the higher-order frequency of the structure itself is relatively small;When the self frequency is similar to the peak frequency of the seismic wave response spectrum,it is more reasonable to choose the structural fundamental frequency and the peak frequency of the seismic wave response spectrum.(4)Based on the research in the first four chapters,a relatively accurate finite element model is established to simulate the dynamic interaction between the ground frame structure,soil layer,and underground station structure,and to study the influence of the ground structure on the seismic response of adjacent subway station structures.The influence of factors such as the number of floors,spacing,and foundation form on the seismic response of subway stations was discussed separately.The results show that the degree of influence of ground structure factors on subway stations is: number of floors>distance>foundation form.Numerical analysis methods are widely used in seismic research of subway stations,and the research results in this paper aim to provide more reference for improving the accuracy of such numerical simulations.Figure [28] Table [25] Reference [61]... |
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