Seismic response of irregular RC buildings designed for gravity and seismic loads

Irregular reinforced concrete framed buildings are peculiar and their seismic response is difcult to predict using simplifed approaches. The irregularity in structural confguration is characterized by cross-sectional area reduction of the columns along the height, in-elevation and in-plan irregular distribution of the masses, complex foor geometry or foor geometry variation along the height. This study analyses the seismic response of several four-storey buildings with diferent types of irregularities, namely in-elevation foor height and foor geometry variation. Additionally, responses of both seismically designed and gravity load designed structures are compared for each geometry considered. A numerical model accounting for non-linear fexural and shear response of the structure is developed, aimed at conducting non-linear incremental dynamic analyses. The results are discussed in terms of inter-storey drift, foor acceleration profles, fragility functions and foor response spectra. A signifcant infuence of the irregularity on foor accelerations and displacements was observed, as well as on the spectral acceleration at collapse, mainly caused by mass and stifness variation along the height. On the other hand, no signifcant infuence was detected on failure modes.