Study On Vibration Comfort Of Buildings At TOD Developed Metro Depot

In recent years,under the guidance of the Transit-Oriented Development(TOD)model,the traditional metro depot used for parking and maintenance as the high-grade office and residential land development mode has become an important measure to return the funds of subway construction.However,the vibration caused by frequent train operation at night(22:00-06:00)has seriously affected the comfort level of residents in the over-track buildings,which has become a key bottleneck restricting the development of over-track buildings.In order to solve the above problems,this thesis summarizes the evaluation standard system of vibration comfort level at home and abroad through literature research,and obtains the multi-index correlation data of typical metro depot through field testing,and studies the feasibility of conversion of different evaluation indexes from the aspects of time-frequency characteristics,energy loss and coherence of vibration transfer path,index conversion methods and so on.Finally,based on a typical case,the vibration comfort of an over-track building is evaluated.The specific research work and relevant conclusions are as follows:(1)Selection of evaluation index of vibration comfort of over-track buildingsThrough combing the current research on vibration comfort evaluation of building structures,environmental vibration evaluation of buildings can be divided into normative index limit value evaluation and vibration annoyance rate evaluation,and there are differences in measurement quantity,evaluation quantity and counting weight between different evaluation methods,where measurement quantity is divided into two categories: acceleration and velocity.On the other hand,since different human bodies respond differently to vibration,the annoyance rate is more capable of quantifying the impact of vibration on the comfort of residents.(2)The acquisition and influence analysis of correlation data based on field testTo obtain the correlation data between different evaluation systems,two sensors of acceleration and velocity were installed on an over-track building for field testing.The measuring points are located under the cover of the vibration source-station structure column-building structure beam plate column,which forms the vibration test of the whole transmission path.Among them,the use of shunting to expand multiple sets of pull bellows tests ensures data repeatability.The analysis results of the influence on the vibration data show that the vibration intensity is highly correlated with the running speed of the train.As the speed increases,the vibration intensity increases.The closer the train runs to the station structure column below the building,the greater the vibration intensity generated;The transmission pattern of vibration between building floors shows the law of first decreasing,then increasing,then decreasing,and the maximum vibration intensity appears in the upper-middle floor of the building.(3)Feasibility analysis of different evaluation index conversionThe feasibility of different evaluation index conversions is studied from the aspects of time-frequency characteristics,energy loss and coherence of vibration transmission path,and index conversion method analysis.The results show that the energy loss of acceleration and velocity and the coherence of the two measuring points are not completely consistent in the transmission process.The energy distribution of vibration acceleration and velocity of building floor measuring points in the spectrum is basically the same,and the response peak appears at the natural frequency of the floor.In terms of acceleration conversion velocity,the three methods of formula calculation based on 1/3 octave,calculus calculation based on spectrum and calculus calculation based on time history are all within 50～200 Hz and the measured velocity error is within 4.5%.In the evaluation of vibration comfort,the acceleration and velocity are consistent with the results of the standard evaluation.The Norwegian annoyance rate evaluation method shows that the annoyance rate using acceleration measurement is higher than the velocity.Among them,the maximum difference between the evaluation results of acceleration and velocity in affecting residents’ rest is4%.In summary,the acceleration and velocity evaluation indexes cannot be directly converted.(4)Vibration comfort evaluation of an over-track buildingThe research results of this case show that when using Chinese JGJ/T 170-2009(acceleration)and American FTA standard(velocity)to evaluate the vibration comfort of the over-track building,both can meet the comfort requirements;when using annoyance rate evaluation,the environmental vibration induced by the metro depot affects the residents’ comfort,but can ensure that 90% of the residents are protected from high annoyance;In the special case of the metro depot,the main negative impact on the residents’ vibration comfort often occurs in the early morning and late night peak hours,which can lead to sleep interruptions.Therefore,the evaluation index should consider more factors related to sleep difficulties and wakefulness thresholds.