Discussion of paper: “Estimating optimum parameters of tuned mass dampers using harmony search” [Eng. Struct. 33 (9) (2011) 2716–2723]

In the aforementioned paper, optimum design of tuned mass dampers (TMD) installed on multiple degree of freedom (MDOF) structures under seismic excitations is proposed. Equations of motion for structures with and without TMD were solved by the modal analysis procedure. Results of numerical studies in this discussion show that using modal method for solving the differential equations governing the motion of controlled structures by TMD dampers usually is not corrected because such systems essentially have not classical damping.