Seismic vulnerability of reinforced concrete buildings with discontinuity in columns

Irregular reinforced concrete (RC) buildings constitute a significant portion of the existing housing stock. A common type of irregularity is in the form of discontinuity in the vertical framing elements, which can exacerbate their seismic vulnerability. The design guidelines available in seismic design codes essentially cater to only regular buildings, and the safety of such buildings, even when the other guidelines of the codes are followed, is doubtful. This article evaluates the vulnerability of RC frame buildings with discontinuity in columns designed for modern seismic codes, in the form of seismic collapse capacity, collapse resistance against maximum earthquake demand level, and failure mechanism. The adequacy and limitations of the provisions of the seismic design codes are evaluated for such buildings. Analysis results show that the sequential analysis of buildings considering the construction staged effects, considerably affects the design and hence the collapse failure mechanism of even low- and mid-rise buildings. The results also underline the importance of strong column-weak beam design in the seismic performance of the floating column buildings. The vertical component of ground motion is also observed to be relatively more crucial in floating column buildings.