Geotechnical seismic isolation for low‐to‐medium‐rise buildings using sand-rubber deformable layer

The high costs of base-isolation systems is one of the obstacles for their application in developing countries. In this research, a low-cost base-isolation system for low-to-medium-rise building has been proposed. For this purpose, a soil layer with plain sand or sand-rubber mixture is applied under building base. To provide lateral movement, a gap is created around the soil layer and filled with flexible materials. This gap let the layer have shear deformations and thus the amplitude of the structural response will be potentially decreased. To evaluate the performance of the proposed base-isolation system, several models have been developed in OpenSees software, with the aim to study the effective factors: the type of layer material, gap width and layer thickness. In these models, a 9-story structure of steel moment frame system including soil layer with the prescribed factors has been analysed by nonlinear time-history analysis procedure with appropriate ground motion records. To evaluate the performance of the proposed base-isolation system, the responses of peak story drift, peak story displacement, maximum axial force of the column and maximum rotation of the plastic hinge of the beam in different models have been compared. The results show that the proposed system, have been very effective in reducing the structural seismic responses. The base-isolation with sand-rubber mixture and layer thickness of 0.5 m and gap width of 10 cm, showed the best performance.