Vibration propagation law within over-track buildings above throat area of metro depot

Relying on a metro depot with over-track buildings in Shenzhen, the vibration acceleration responses during trains passing on different tracks in the throat area were measured on-site at the ground floor, platform transfer floor, and the over-track 4-storey steel-framed structure. The propagation laws of environmental and structural vibrations caused by train operations in the throat area were analyzed. Research results show that there exists energy loss when the train-induced vibration propagates from the surrounding soil to the foundation through the soil-structure dynamic interaction. The measured acceleration amplitude at the foundation bottom of the structure is significantly smaller than that at the adjacent ground surface. In the process of train-induced vibration propagation from the surrounding soil to the structure, the high-frequency component above 50 Hz attenuates more rapidly. The soil-structure coupling loss can be up to 27-34 dB. Therefore, the influence of soil-structure coupling loss should be considered when using the foundation bottom inputs to predict the train-induced vibration responses within the over-track buildings at metro depots based on the substructure method. The vibrations at the foundation bottom of the platform columns should be used as the vibration input of the model. The structural designs of over-track platform and transfer floor can help to reduce the upward propagation of the train-induced vibration to some extent. The acceleration level attenuation amplitude is 3-6 dB. The train-induced vibration propagates upward through the platform columns in the form of axial wave and spreads horizontally through the transfer beams and floor slabs in the form of bending wave. The vibration energy has multiple paths to propagate toward the over-track building and superpose. The vibration difference among measuring points on the platform transfer floor is within 8 dB. The vibration propagation law between floors in the over-track building depends on the impedance ratios of beam to vertical load-bearing structure and floor slab to vertical load-bearing structure. Increasing the impedance of the beam or floor slab helps to reduce the upward propagation of vibration. The train-induced vibration frequency within the 4-storey steel-framed structure has three peaks at 6.3, 12.5, and 40.0 Hz, respectively. It is related to the natural frequency of the structure and the dynamic characteristics of the excitation. © 2022, Editorial Department of Journal of Traffic and Transportation Engineering. All right reserved.