Serviceability Analysis And Vibration Control Of Elevated Metro Depot And Over-depot Residential Building Complex

The metro depot of the urban rail transit system is characterized by occuping a large amount of land resources with low building density,and it proves to be an effective way to realize intensive land use by exploiting real estate over the metro depot.However,the train-induced vibrations and re-radited noise would inevitably affect the living quality of the building occupants,thus impairing the potential development value of the metro depot.In this paper,vibration response of a building complex comprising an elevated metro depot and the over-depot residential building is investigated through theoretical analysis,field measurement,numerical simulation and vibration control study.In detail,this study includes contents as follows:(1)Vibration responses of the train-track system under low-speed vehicles were studied.The contact force between the rail and wheel was divided into the quasi-static load,the dynamic load and the impact load,and these three types of load were solved separately.Vibration responses from the quasi-static load and the dynamic load were solved using a non-iterative procedure,which was based on the proposed vehicle-track coupling model,and vibrations from the impact load were solved through the finite element model capable of describing the local details of the wheel and rail joint.The models were validated by the test data of two rails,where one rail with joint and another rail without joint were measured.Besides,the influence of train speed and fastener paramaters on vibration was investigated based on the proposed models.(2)Theoretical analysis was conducted on the train-track system and the over-depot building.A theoretical model of the train-track system was proposed and the frequency domain response was solved by applying Fourier Transform to the partial differential equation of the rail,so as to avoid complex computation in the time domain.Besides,A theoretical model of the building system was proposed based on the dynamic stiffness method,where the floor was treated as a single element and the interaction between the floor slab and the beams was considered.Sturctural response was solved based on the global dynamic stiffness matrix,which was obtained by applying Fourier Transform to element vibration equations.The influence of train,track and depot parameters on vibration was investigated,and analyses showed that it was inefficient to control vibration by changing the fastner stiffness or damping under a low-speed train,while desirable mitigation effect could be achieved by enlarging the section of the depot columns,and it exhibited a mitigation better effect than enlarging the beam section or slab thickness.(3)Field measurement was carried out to investigate the vibrations of a building complex comprising an elevated metro depot and the over-depot residential building.Acceleration responses were measured and compared at different locations in terms of time domain and frequency domain,and the influence of train position on structure vibration was studied as well.Vibration serviceability of the building complex was evaluated and compared using different indicators in various codes.Besides,an “annoyance” indicator based on fuzzy mathematics and probability theory was adopted to evaluate the vibration serviceability in the statistical sense.Regardless of the selected indicators,the results showed that vibration levels of certain locations have exceeded the threshold and mitigation measures have to be taken.(4)Numerical simulation of the vibration response was performed on the building complex.Finite element model of the elevated depot-residential structure was built using the software ANSYS.Vibration response of the structure was solved using the simulated vehicle excitations and the results were validated by the test data.Based on the model,the train-induced vibrations were investigated in the same floor and compared at different floors,so as to give an insight into the vibration distribution and attenuation characteristics.Partition wall stiffness on structure dynamic properties was studied based on the model.The influence of slab thickness and column section on vibration was studied as well,so as to provide references to vibration control.(5)Mitigation measures for the over-depot residential building were discussed.The mitigation effect of using vertical bearings and the influence of bearing stiffness was investigated by the established theoretical and finite element model.Besides,a novel isolation slab structure was proposed to realize local mitigation of the building by changing the vertical frequency of certain floor slabs,frequency characteristics of the slab and its mitigation effect were studied as well.