Experimental and analytical investigations on compressive behavior of thick rubber bearings for mitigating subway-induced vibration

Abstract

When designing over-track buildings, two main problems require attention: the lateral stiffness changes abruptly between superstructures and the podium, and the subway-induced vibration leads to occupant discomfort. As one type of three-dimensional isolators, thick rubber bearings (TRBs) are considered as an effective measure to overcome these problems. However, the extension of the experimental knowledge base concerning the compressive behavior of TRBs is needed to develop analytical methods to precisely predict their vertical stiffness. Also, the effects of geometric parameters and loading conditions on the vertical stiffness of TRBs are required to be examined by experiments. For these purposes, a total of 6 full-scale thick natural rubber bearings (TNRBs) and 4 full-scale lead thick rubber bearings (LTRBs) were designed, and a series of compressive tests were conducted. The geometric parameters included the first and second shape factors (S1 and S2), single-rubber layer thickness, and core configuration (without and with the lead core). Various load amplitudes and vertical pressure were considered. The experimental results showed that the vertical stiffnesses of the TNRBs and LTRBs reduced with the decrease of the S1 and S2, and the lead core had a significant effect on the vertical stiffness of the LTRBs. The change of the load amplitude for the LTRBs and the vertical pressure for the TNRBs also remarkably affected their vertical stiffnesses. Based on the experimental campaign and existing test database, the experimental values of vertical stiffness of TNRBs and LTRBs were compared with current analytical formulations. Finally, analytical methods for determining the vertical stiffnesses of the TNRBs and LTRBs were developed, respectively, which showed good agreement with the test results.