Investigation of the effects of local soil conditions on the seismic performance of existing buildings with different concrete classes through nonlinear time history analyses

Our country, located in a geologically high seismic risk zone, has experienced many painful experiences and suffered significant loss of life and property due to various earthquakes occurring at different times and locations. Especially as a result of consecutive earthquakes that occurred in Pazarcık and Elbistan districts of Kahramanmaraş on February 6, 2023, around 51 thousand people losing their lives, approximately 107 thousand people getting injured, and numerous buildings collapsing or becoming severely damaged have raised questions about the reliability of the existing building stock. It is known that a significant majority of these buildings, which are quite old, have not been designed in accordance with the Turkey Building Earthquake Code 2018. Taking into account the inability to professionally meet the necessary standards during the conditions of their construction era, the reliability of existing structures, particularly in terms of material quality, can become even more questionable. Within the scope of the study, two 5-story reinforced concrete buildings, assumed to exist in areas belonging to local soil classes Z2 and Z4, have been designed for the C25 concrete class to comply with the requirements of the Turkish Earthquake Code 2007. The seismic performance of these building models has been assessed based on deformation using the non-linear time history analysis method outlined in the Turkey Building Earthquake Code 2018, considering local soil classes ZB instead of Z2 and ZD instead of Z4. Additionally, although designed for C25, the possibility of existing structures being constructed with C10 and C16 concrete classes due to issues during production or application stages has also been investigated. During the analysis conducted under historical earthquakes, bi-axial earthquake records scaled with a simple scaling process were used. The damage states of structural elements due to bending and shear deficiencies were assessed for six different buildings created by considering concrete and local soil classes. In cases where the local soil class is assumed to be ZB, it is observed that the building models considered meet the Controlled Damage Performance level, while in cases where it is assumed to be ZD, they are seen to be in a Collapse Situation. The shear force and plastic hinge rotation ratios, albeit with exceptions, have decreased due to the decrease in concrete compressive strength.