Research On Vibration And Vibration Isolation Of Superstructure Caused By Subway Operation

The shortage of urban land resources in my country is becoming more and more serious,and many cities try to alleviate the problem by developing superstructures along the subway lines.However,the vibration generated by the collision between the wheels and the track duri ng the operation of the subway is transmitted to the superstructure through the track foundation,foundation and building foundation.The vibration of the superstructure of the subway seriously affects the living quality of the residents.How to effectively control the impact of subway vibration on the superstructure has become a key issue in the development of the superstructure of the subway.In this paper,theoretical analysis,field measurement,numerical simulation of subway vibration and vibration con trol are carried out for the vibration problem of the superstructure of the subway.The specific work is as follows:(1)Summarize the research results of the superstructure vibration caused by subway operation at this stage,including the vibration mechan ism of subway wheel-rail action,the propagation law of subway vibration waves in soil and superstructure,and the control principle of subway vibration in superstructure..And determined the subway vibration comfort evaluation system with the vertical acceleration amplitude and the frequency division maximum vibration level as the vibration evaluation index.(2)On-site ground acceleration was measured for ground vibration caused by subway operation,and three groups of ground vibration acceleration time histories during subway operation were obtained.The acceleration time-history analysis was carried out in the time domain and frequency domain,and it was obtained that the dominant frequency of subway vibration was distributed between 30 and 100 Hz,and the three groups of measured ground subway vibration intensity all exceeded the specification limit.The obtained measured subway vibration data is used as the numerical excitation for the subsequent finite element analysis model.(3)Establish a multi-degree-of-freedom impedance model based on the impedance model theory,and study the influencing factors of the propagation law of subway vibration in the impedance model,including the number of building floors,the section size of load-bearing vertical members,the thickness of the floor and the elastic modulus of concrete on the vibration.Influence of propagation laws in architecture.The results show that the propagation law of subway vibration is different in buildings with different floors.Generally speaking,the vibration of high-rise buildings is larger than that of low-rise buildings.At the same time,reducing the size of load-bearing components,increasing the thickness of floor slabs,and reducing the strength of concrete can all be weakened.Tran smission of vibrations in buildings.(4)Establish the overall finite element model of the foundation-superstructure of the three proposed superstructures(cultural and educational buildings),study the transmission law of subway vibration in the building structure,and evaluate the comfort of the vibration at the evaluation point.On this basis,the influence of the characteristics of the superstructure on the vibration transmission is compared and analyzed,including floors,structural complexity,and vertical vibration characteristics of the structure.The results show that the vertical vibration intensity decreases with the increase of floors,and the more complex the structure,the better the attenuation effect of vertical vibration,especially the high frequency vibration of 60~80Hz.At the same time,the building structure is most sensitive to the vertical vibration of 5~15Hz.(5)Based on the two-degree-of-freedom vibration isolation theory,the vertical vibration frequency ratio-transmittance function is derived,which is mainly controlled by the subway vibration frequency and the vertical natural vibration frequency of the superstructure.On this basis,a vertical vibration isolation layer is set for the proposed superstructure,and it is analyzed th at the vibration isolation effect is affected by the design frequency of the vibration isolation layer,the vibration characteristics of the subway,and the complexity of the superstructure.The results show that the vertical vibration intensity of the superstructure is reduced below the specification limit after vertical vibration isolation is adopted.The vibration isolation effect varies with the lower the vertical design frequency of the vibration isolation layer,the better the vibration isolation effe ct.The larger the subway vibration dangerous frequency point,the better the vibration isolation effect.The more complex the superstructure,the worse the vertical vibration isolation effect.This paper provides theoretical guidance and scientific basis for solving the vibration problem of subway superstructure through the research of subway depot and its superstructure,and proposes an effective vibration prediction and control design method.