Experiment investigation and in situ test of hybrid vibration bearing system applied to overtrack historical buildings

The metro-induced vibrations and seismic safety are both big issues for historical buildings in modern cities. This paper proposed a novel hybrid vibration bearing (HVB) to isolate horizontal earthquakes and mitigate vertical metro-induced vibrations. The HVB consists of lead rubber bearing and thick rubber bearing with decoupled horizontal and vertical behaviors. The mechanical model of HVB is developed, and a new vertical stiffness formula of thick rubber bearing is proposed to calculate the compression stiffness, without conducting test. A static test of the prototype HVB and a dynamic experiment of an SDOF system were performed. The bearing has stable behavior under different pressures and lateral deformations. The bidirectional test confirmed the decoupling characteristics. The isolation design and retrofitting of an overtrack historical building was conducted. After retrofitting, the average maximum vibration level and the average subfrequency vibration level decreased 25% and 18%, respectively. The horizontal accelerations of isolated structure were 65% to 70% of the input, and the shear strains of bearings were smaller than 200% under rare earthquakes. Finally, case study of structures with different types of foundations is introduced. The vibration mitigation efficiency of different structures is confirmed.