In this paper an effective method has been proposed for designing optimal multiple tuned mass dampers (MTMDs) to mitigate the seismic response of structures based on defining an optimization problem which considers the parameters of tuned mass dampers (TMDs) as variables and minimization of maximum structural response as an objective function while a number of constraints have been applied on TMDs response and parameters. The genetic algorithm (GA) has been used successfully for solving the optimization problem. For illustration, for a ten-story linear shear frame subjected to a filtered white noise excitation optimal MTMDs have been designed. The results have shown the simplicity and convergence behavior of the method. It has also been concluded that the performance of MTMDs depends on TMDs mass ratio, TMDs configuration and design criteria where increasing the TMDs mass ratio has improved monotonously the performance of MTMDs especially for the domain of smaller values of the mass ratio, while for this case study the number of TMDs has not been more effective. Testing the optimal MTMDs under near-field and far-field earthquakes shows that the performance of MTMDs has been influenced by input excitation. The capability of the method in considering the effect of higher modes has been shown.

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Summary Direct displacement‐based design (DDBD) approach is one of the most effective performance‐based design methods. In this paper, a modified version of DDBD is proposed for the design of structures equipped with fluid viscous damper (FVD) that the effect of higher modes and difference between spectral velocity and pseudo‐spectral velocity are applied in the design process. Different steel moment frames equipped with FVD have been designed using the proposed method, and the achievement of desirable performance level has been evaluated under different earthquake records. For comparison objectives, the performance of the modified method has been compared with the previously proposed DDBD. Although the structures designed using the previously proposed DDBD have achieved the desirable performance level, the peak story drift is significantly less than the target drift and this design approach leads to an expensive overdesign, whereas in the structures designed using the modified DDBD, the peak story drift is close to the target drift and the achievement of desirable performance level has been effectively satisfied. Therefore, the drawback of overdesign has been solved, and the modified version of DDBD can be considered as an effective design approach for structures equipped with FVD.

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