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The nonlinear dynamic response of slender structure is an important topic in the structural engineering. Specially, when this kind of structures are under the action of seismic loads, which have a big frequency content, and it is considered a base system with elasto-plastic behavior, which may cause important modifications in the system response by the increase of the nonlinear effects. In these cases, the determination of the nonlinear behavior in frequency domain gives a useful information about the potential impact of the earthquake’s frequency content over the structure behavior, as well as the possible change in the frequency properties of the system during a seismic event. Even more, if the frequency content of the excitation is concentrated near the resonant regions of the structural system. In this work, a numerical scheme for the calculation of the frequency domain behavior of the time domain nonlinear responses, also known as time-frequency analysis, of slender frames under seismic actions is presented. For this, the Short Fast Fourier Transform (SFFT) technique is applied over the time domain nonlinear response of slender frame which rest on a base with elasto-plastic behavior. In addition, two numerical techniques to obtain SFFT are assessed investigating the accuracy of both the numerical schemes. Real and synthetic earthquake acelerograms are considered as dynamic excitations. Finally, the synthetic excitations are obtained considering a concentrate frequency content near the two first resonant region of the structure.