Evaluation of Building Base Isolation Performance in a Test Bench

Recently, in the frame of the EUROSTAR research project entitled "Building Insulation against Outdoor Vibrations" (BIOVIB), a test bench has been developed in CDM laboratory to determine the isolation performance of Building Base Isolation (BBI) systems. The test bench consists of three main parts: (1) a superstructure, (2) isolation bearings and (3) a substructure (foundation). The superstructure consists of a concrete column and four steel blocks being hanged from the column by four springs to represent the effect of floors resonance frequencies. The substructure (foundation) is a thick steel plate supported by four thin pads adjusted to dynamically behave as a real foundation. In this test bench, the isolation efficiency can be directly determined as the difference between the vibration level at the superstructure in a non-isolated build-up and that obtained in an isolated one. However, in practice, such a direct comparison between the isolated and non-isolated building cannot be undertaken. Using an isolated and a non-isolated setup, the performance of a BBI system (CDM-SEB) has been evaluated. Finally, the performance of the system in terms of the insertion loss has been compared with that obtained by an insertion gain indicator defined in terms of the isolator transmissibility and the superstructure and substructure mobilities. Results show a reasonable agreement between the proposed insertion gain indicator and the direct insertion gain obtained from the measurement in the test bench.