عنوان مقاله [English]
Estimating the real dynamic properties of a structure using a Direct Displacement Based Design (DDBD) is less computationally time-consuming than nonlinear dynamic analyses. Use of an equivalent linear system is associated with the effective period and effective damping for desired ductility and serviceability level of the structure model, which helps to estimate the nonlinear response.By using this technique, the effective stiffness and percent of cracking on the structure can be calculated. In this paper a 96 number of low-medium rise reinforced concrete frames were analyzed for extraction the relation between effective periods and damping ratio with ductility. The frames have one-six stories with different span lengths.The results of the analyses showed that the period and damping ratio is increased by increasing the ductility.But increasing the dynamic properties of frames did not have the same percent. However, the length of spans decreased the fundamental, effective period and effective damping of the frame with the same rise, but the change was minimal.