Study On Influence Of Vibration Induced By Metro Operation On Ancient Wooden Structure

The speed of Chinese urbanization process is gradually increased.The size of urban population is expanding rapidly,and the metro lines are also extending because of the city expansion.Therefore,the vibration pollution problem of metro operation emerge gradually,and become one of the key factors which restrict the construction of urban rail transit.It worth mentioning,the most important problem is its impact on the historical and ancient buildings in the city.A comprehensive study of the dynamic response of ancient buildings under the influence of subway vibration,which is important for the development of vibration reduction and isolation measures for ancient buildings,is of great significance for reducing the harm of environmental vibration to ancient buildings.Taking the Northern Gate,which is an ancient wooden structrue of the Summer Palace,as an example.This paper explores the vibration influence of Beijing Metro Line 4 on the ancient wooden structure buildings.The main work is as follows: First,the site vibration test of the Northern Gate wooden and its nearby site is carried out,and the vibration condition of the site surface and the interior of the ancient building is obtained preliminary;Next,according to surveying and mapping data of the structrue and site plan,using the large-scale general finite element software ABAQUS to establish the coupling model of ancient wooden structure-soil foundation-tunnel.After obtain the vibration response of foundation and structure under realistic site condition which is calculated by simulation,it is compared with the site measured results in order to verify the correctness of the model accuracy.Finally,using the approach of variable controlling,change the corresponding parameters in the finite element model to research the influence of different factors on the vibration response of ancient building,which is caused by subway operation.After the above researching work,the following conclusions are obtained:1)Compared with the background environment vibration,the horizontal vibration intensity of the ground surface increases significantly when the subway passes by.With the increase of the horizontal distance from the site to the metro line,the vibration attenuation is obvious.The vibration attenuation rate is gradually reduce with the increase of the distance.The attenuation of the horizontal vibration velocity peak within the distance from 0 to 25 m accounts for about 70% of the total attenuation within the distance from 0 to 100 m.In the process of vibration propagation,the decay rate of high-frequency vibration energy is much higher than that of low frequency.In the frequency range of 0～50Hz,the horizontal vibration frequency above the tunnel is mainly concentrated above 40 Hz.When the vibration propagates to the site which is 100 meters from metro line,the proportion of low frequency vibration increases significantly due to the fast attenuation of high frequency vibration,and the frequency spectrum curve has a significant peak value in the range of 0～20 Hz.2)When the horizontal vibration caused by the subway is transmitted from the base station to the second floor of the beigongmen building,there is obvious amplification phenomenon,and the horizontal vibration response of the structure is mainly concentrated in the frequency band of 0 ～ 20Hz;the measured results are compared with the vibration limits of ancient buildings in the Chinese code,and the vibration level of the beigongmen building of the summer palace is in a safe range.3)Through the analysis of the dynamic characteristics of the wood structure of beigongmen,through the simulation calculation and comparative analysis of various working conditions,the increase of the train speed and the decrease of the horizontal distance between the ancient building and the subway line,the decrease of the buried depth of the tunnel will increase the vibration intensity of the wood structure and the ancient building to varying degrees,and it is found that the vibration intensity of the building orientation and the wood structure of the ancient building is relatively strong When the long axis of the building is parallel to the direction of the subway,the overall vibration intensity of the ancient building is large.