A study on mitigation of interstory drift concentrations in reinforced concrete frames under earthquake demands

Abstract

Site observations and analytical studies show that low-rise RC frames have larger interstory drift ratios at the lower stories under earthquake loading. It is obvious that due to the localization of drifts, these structures could reach their capacity limits earlier than a system with a well-distributed drift among its stories. This phenomenon is especially vital for frames with limited drift capacity and could cause them to fail below the specified design demands. The existing stock of seismically deficient RC frames in Turkey, and for that matter all over the world, are in this group. The presented study investigates the effects of a pre-organized stiffness distribution along the building height to mitigate the interstory drift concentrations. As a case study, the readily available infill walls were used for stiffness-modifying elements to obtain the organized stiffness distribution. Initially, the numerical model was calibrated and verified using the experimental results. Afterward, three planar frames were studied. These were a bare frame and two frames with infill walls. Nonlinear dynamic time-history and pushover analyses were performed to evaluate the seismic performance of the frames. The results indicate that the organized stiffness distribution could mitigate the interstory drift concentrations and provide a better distribution of interstory drift ratios along the height of the frames.