Field measurement and evaluation of noise and vibrations induced by bridge cranes in full-scale over-track buildings.

Abstract

Over-track buildings have been increasingly favored in the construction of metro depots and freight depots in China in the last decade due to advantages of intensive utilization of land resources and high-profits. However, due to the relatively heavy transportation mass and high-operating frequency of bridge cranes, over-track buildings are often complained by occupants for annoying noise and vibrations. So far this issue is rarely concerned and the characteristics of noise and vibrations under bridge crane loading remain unclear. In this study, field measurements of two full-scale over-track buildings, including a seven-story building over a metro depot and a three-story building over a freight depot, were conducted. Vibration characteristics of both the structure and the bridge crane were obtained. The transmission of vibrations from bridge crane system to the over-track building was obtained by transfer function (TF) of vibration from the column bracket towards the outdoor platform or building floors. The structure-borne noise inside the building was also captured and evaluated. The effect of bridge crane operational parameters (loading capacity and running velocity) and structural dynamic properties (non-structural components) on system responses was further discussed. Results show that the bridge crane-induced vibrations are comparable to the levels of train-induced vibrations. Besides, both buildings tested in this study suffer from unacceptable structure-borne noise, although the building vibration is acceptable. We recommend to carefully examining design of new over-track buildings to avoid annoying indoor noise and improve the living or working environment of occupants. It is demonstrated that vibrations of over-track buildings are more sensitive to running velocity than load capacity of bridge crane. It could be expected that the future increase of velocity will worsen the noise and vibration environment of over-track buildings. Furthermore, it is seen that non-structural components would remarkably affect dynamic responses of the building.