Re-evaluation of building damage during recent earthquakes in Turkey

Over the past two decades Turkey has been hit by several moderate to large earthquakes that resulted in significant loss of life and property. A remarkable number of casualties and heavily damaged or collapsed buildings has emphasized inadequate seismic performance of multistory reinforced concrete buildings, typically three to seven stories in height. This study aims to evaluate seismic performance of the most common reinforced concrete building stock in Turkey considering nonlinear behavior of the components. A sample building set is selected to reflect existing construction practice; regular buildings and buildings with irregularities such as soft story, heavy overhangs, short columns, and soft story with heavy overhangs. Ductile and non-ductile details are taken into account by transverse reinforcement amount. Capacity curves of the investigated building set are determined by pushover analyses conducted in two principal directions. The inelastic dynamic characteristics are represented by equivalent single-degree-of-freedom (SDOF) systems. Their seismic displacement demands are determined using nonlinear response history analysis under selected ground motions. Seismic performance evaluation is carried out in accordance with the recently published Turkish Earthquake Code (2006) that has similarities with FEMA-356 guidelines. Analytical damage evaluation in this study has shown that the seismic effects of earthquakes experienced in Turkey are significant and some of the earthquakes impose excessive displacement demands. Therefore, a considerable portion of existing building stock may not be safe enough in Turkey or similar countries. Also, it is observed that structural irregularities affect seismic performance of buildings. Short columns and soft story with heavy overhangs have the most negative effect.