Experimental Investigation Into Natural Base Isolation System for Earthquake Protection

This paper presents the results of experimental investigations into the performance of a well-designed layer of sand, and layer of sand mixed with shredded tire (rubber) as low cost base isolators. The building foundation is modeled by a 200 mm by 200 mm and 40 mm thick rigid plexi-glass block. The model footing is placed in the middle of a 1m by 1m tank filled with sand. The selected base isolator is placed between the footing and the sand foundation. The whole setup is mounted on the shake table and subjected to sinusoidal motion with varying amplitude and frequency. Acceleration values at the shake table, inside the isolation material, and on top of the footing are measured. The displacement of the footing is also measured. The sand is found to be effective only at very high amplitude (˃ 0.65g) of motion. Among all the different percentage of shredded tire in sand tested, the performance of a layer of 50% shredded rubber tire and sand placed under the footing is found to be most promising as a low cost effective base isolator