Performance of buildings with seismic base isolation made of experimentally examined sand-rubber-asphalt elements

Base isolation is an effective method for reducing the effects of earthquake shaking transferred from the ground to the superstructure. However, this method is not widely used, especially in developing countries, due to its high cost. The usability of low-cost sand-rubber-asphalt (SRA) mixtures for seismic base isolation of medium- and low-rise structures was investigated in this study. Monotonic and cyclic triaxial tests were performed to obtain damping and other mechanical properties of the SRA mixtures that contain different amounts of crumb rubber. According to the experimental findings, the hysteretic damping of SRA mixtures with 4% rubber content (SRA4) is notably high, and the mixture exhibits more ductile behavior compared to others. Three-dimensional (3D) structural models with different numbers of storeys were simulated with the finite element method to evaluate the effects of seismic isolation elements made of SRA4. The isolation elements of different sizes were placed under the foundations of the superstructures, and two earthquake shaking records—with different maximum ground accelerations (PGAs)—were applied to the models. The analyses showed that the maximum roof acceleration of the structural models with the foundation isolation can decrease by up to 65% compared to the fixed-base models. Furthermore, an increase in the earthquake's PGA enhances the efficiency of this new type of foundation isolation system. This new isolation system shows similar performance to lead-rubber bearing isolation systems used in lowrise and mid-rise buildings.