Deflection amplification factor for estimating seismic lateral deformations of RC frames

Different values have been assigned to the ratio of the deflection amplification factor (C _d) to the response modification factor (R) for a specified force-resisting system in the seismic design provisions while the same application is defined for it. An analytical study of the seismic responses of several reinforced concrete frames subjected to a suite of earthquake records performed in this research indicate that the stories’ overstrength and stiffness distribution along the structural height can affect local deflections more than global ones. Therefore, the C _d/R ratio is calculated based on the ratio of both maximum inelastic to maximum elastic displacements and interstory drifts. Due to damage concentration in some specific stories, the deflection amplification factor calculated based on inelastic interstory drifts was larger than that of the inelastic displacements. Consequently, a minimum value of 1.0 is recommended for the C _d/R ratio in order to estimate maximum inelastic drifts. The ratio of inelastic to elastic displacement was generally found to increase slightly along the structural height for the studied RC models. In addition, it was detected that the story damage indices of the studied RC frames decrease when the inverted value of inelastic interstory drift ratios are increased through a (negative) power form.