Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 49 2 2017 07 23 Designing Variable Stiffness Semi-Active Tuned Mass Damper for Nonlinear Structures Designing Variable Stiffness Semi-Active Tuned Mass Damper for Nonlinear Structures 347 362 704 10.22060/ceej.2016.704 FA M. Mohebbi Engineering Department , University of Mohaghegh Ardabili, Ardabil, Iran S. Bakhshinezhad Engineering Department , University of Mohaghegh Ardabili, Ardabil, Iran Journal Article 2014 01 31 In this paper, designing variable stiffness semi-active tuned mass damper (SATMD) for<br />mitigating the responses of nonlinear structures under earthquake excitation has been studied. Two semiactive control algorithms based on instantaneous optimal control and clipping control concept as well as<br />modified balance control have been developed to determine the optimal stiffness of SATMD for nonlinear<br />structures in each time step. For determining optimal parameters of semi-active control system including<br />the weighting matrices in performance index of control algorithm as well as the maximum and minimum<br />values of SATMD stiffness, an optimization problem for minimization of structure maximum response has<br />been defined where genetic algorithm (GA) has been used for optimization. For numerical simulations, an<br />eight-story nonlinear shear building with bilinear hysteresis behavior has been subjected to a white noise<br />excitation and optimal SATMDs have been designed. The results showed that optimal variable stiffness<br />SATMD using both control algorithms has been effective in suppressing the seismic responses of nonlinear<br />structure. Also, variable stiffness SATMD shows better performance than TMD and variable damping<br />SATMD in structural response controlling. Comparing the performance of the variable stiffness SATMD<br />under testing earthquakes which were different from design record, showed that the efficiency of SATMD<br />depends on the characteristics of excitation, hence design record needs to be chosen properly. In this paper, designing variable stiffness semi-active tuned mass damper (SATMD) for<br />mitigating the responses of nonlinear structures under earthquake excitation has been studied. Two semiactive control algorithms based on instantaneous optimal control and clipping control concept as well as<br />modified balance control have been developed to determine the optimal stiffness of SATMD for nonlinear<br />structures in each time step. For determining optimal parameters of semi-active control system including<br />the weighting matrices in performance index of control algorithm as well as the maximum and minimum<br />values of SATMD stiffness, an optimization problem for minimization of structure maximum response has<br />been defined where genetic algorithm (GA) has been used for optimization. For numerical simulations, an<br />eight-story nonlinear shear building with bilinear hysteresis behavior has been subjected to a white noise<br />excitation and optimal SATMDs have been designed. The results showed that optimal variable stiffness<br />SATMD using both control algorithms has been effective in suppressing the seismic responses of nonlinear<br />structure. Also, variable stiffness SATMD shows better performance than TMD and variable damping<br />SATMD in structural response controlling. Comparing the performance of the variable stiffness SATMD<br />under testing earthquakes which were different from design record, showed that the efficiency of SATMD<br />depends on the characteristics of excitation, hence design record needs to be chosen properly. https://ceej.aut.ac.ir/article_704_f64eac11f2cd8f0efa196f8ad173178e.pdf