SEMI-ACTIVE OF BASE-ISOLATED BUILDING WITH VARIABLE CURVATURE SLIDING ISOLATORS

One of the most popular isolators is Friction Pendulum System (FPS). Recent studies and tests have revealed that using these isolators in near-field earthquakes leads to amplified responses. Recently, passive adaptability characteristics have been introduced in these isolators to remove resonant responses. In adaptable sliding isolators, the restoring force is reduced. Hence, base displacement increases. In this paper, two variable curvature isolators, Variable Curvature Friction Pendulum System (VCFPS) and Variable Frequency Pendulum Isolator (VFPI), are employed in the base-isolated benchmark building. The earthquakes are applied bi-directionally on the horizontal plane, ignoring the vertical ground motion component. The shear type base-isolated benchmark building is modeled as a three-dimensional linear elastic structure with three degrees of freedom at each floor level. Time domain dynamic analysis of the benchmark building is carried out by means of the constant average acceleration Newmark-Beta method. The base-isolated benchmark building is investigated for uniform isolation through the performance criteria and time history response. It is observed that variable sliding isolators performed better than conventional FPS due to their varying characteristic properties that enable them to alter the isolator forces depending upon their isolator displacements, thus improving the performance of the structure. To reduce the displacement of the seismic base isolator, semi-active control method with magneto-rheological damper (MR damper) and wavelet neural network controller are employed. MR damper voltage is calculated by the control algorithm to generate the optimum control force of structure. This controller is optimized by genetic algorithm. Numerical results prove that the use of semi-active control systems performs more successfully in reducing the seismic isolator displacement, in comparison to the increasing coefficient of friction of isolators and passive control.