COMPARISON OF RATIO OF SPECTRAL RESPONSE TO DESIGN ACCELERATIONS WITH THE OBSERVED SEISMIC BEHAVIOR OF RC BUILDINGS DURING FEBRUARY 2023 TÜRKİYE EARTHQUAKES

On February 6, 2023, two earthquakes with M_w 7.7 and 7.6 struck South Eastern Anatolian Region of Türkiye. These earthquakes had varying impacts on the buildings in 11 cities around the epicenter. More than 90,000 reinforced concrete buildings were damaged heavily or collapsed in the earthquake-struck region. It was surprising to observe that several medium-rise buildings, presumably designed according to the most recent seismic design code published in 2018, also collapsed. Therefore, in this study, the spectral response accelerations and the observed seismic behavior of low to mid-rise buildings that have been built after 2018 and experienced heavy damage or collapse are discussed. For this purpose, a database was established, comprising data from 3538 buildings in total. The data represent all low to mid-rise reinforced concrete residential buildings, which are situated in close proximity to the stations that recorded maximum ground accelerations in the earthquake-affected cities of Hatay, Kahramanmaraş, and Gaziantep (i.e. between 0.50 and 1.99 g). These buildings were constructed after 2018 (presumed to have been constructed in accordance with the recent seismic design code in Türkiye). Among these, a subset of 422 reinforced concrete buildings experienced heavy damage or collapsed. The Design and Response Acceleration Spectrums were then obtained using approximate approaches. Afterwards, the natural vibration periods of these buildings were estimated by empirical expressions. Using the estimated natural vibration periods obtained for each building in the database, the corresponding spectral accelerations were determined both from Design and Response Acceleration Spectrums. Thereafter, the ratios of the response to design spectral accelerations were obtained. These ratios were then used for discussing the reasons behind the fact that why a considerable proportion of RC structures remained undamaged or showed slight to moderate damage, despite facing significant demands for strength and ductility, while others suffered from heavy damage and collapse.