Effects of structural irregularities on low and mid-rise RC building response

During the recent earthquakes, it has been observed that structural irregularities are one of the main reasons of the building damage. Irregularities are weak points in a building which may cause failure of one element or total collapse of the building during an earthquake. Since Albania is a country with moderate seismicity which has been hit by earthquakes of different magnitudes many times establishes the need to study the effect of irregularities is well-founded. The main structural irregularities encountered in Albanian construction practice consist of short column, large and heavy overhangs and soft story. In this study, these types of irregularities are considered in two different types of buildings, low and mid-rise reinforced concrete frame buildings represented by 3- and 6- story respectively. Pushover analyses are deployed to get the effect of structural irregularities on RC building response. A building set is chosen to represent the existing construction practice in the region; regular framed building and buildings with irregularities such as soft stories, short columns, heavy overhangs and the presence of soft story with heavy overhangs. The analyses have been conducted by using ETABS and Seismosoft software. Pushover curves of building set are determined by nonlinear static analysis in two orthogonal directions. Comparative performance evaluations are done by considering EC8 and Albanian Seismic codes (KTP-N2-89). From the obtained results, it is observed that low and mid-rise structures with soft story- two sided overhangs and short column are more vulnerable during earthquakes