The impact of variability in rubber mechanical properties on the seismic response of scrap tire pad base isolation systems

Base isolation is a technique that involves decoupling a structure from the ground to deflect and dissipate seismic energy, thereby minimizing the transfer of harmful vibrations to the superstructure. However, its application in underdeveloped and developing countries has been limited due to its size, perceived implementation costs, and the lack of awareness and expertise in these regions. This study focuses on assessing how variations in mechanical properties impact the performance of low-cost scrap tire pad (STP) base isolation systems. Nine STP isolators with high variability were considered and experimentally tested to characterize their properties. They were then numerically employed in three types of buildings, two with square plans and one with a rectangular plan. For each building type, two scenarios were examined: using a uniform isolator type for all columns (Scenario 1) and employing a non-uniform isolator type for each column (Scenario 2), with nine cases for each scenario. The results show that, despite the high variability, the average maximum displacement, base shear, rotation, and acceleration of the two scenarios are approximately similar. Moreover, the increase in maximum displacement due to rotation in the isolation system utilizing non-uniform isolators remained below 10 % on average. Thus, although the variability of mechanical properties of the STP isolators impacts the performance of the considered isolation systems, it remained satisfactory compared to the uniform case.