Mechanical and microstructural investigations on concrete of the collapsed buildings after Kahramanmaraş earthquakes

Abstract

Many cities in Türkiye have been affected by the devastating twin earthquakes in Kahramanmaraş. Following the Kahramanmaraş earthquakes, a field study was conducted to investigate the material characteristics of concrete used in collapsed buildings. The study’s major aim is to examine several parameters of reinforced concrete structures by comparing the samples taken from different locations in the region after the Kahramanmaraş Earthquakes for post-earthquake material characterization. Investigating the effect of concrete damage in these earthquakes, which especially affected 11 provinces and an area wider than approximately 100 thousand square kilometers, is of greater importance. For this purpose, Schmidt hammer measurements were carried out on structural elements, and concrete samples were collected from the same structures. Compression tests were conducted on the collected 21 samples taken from the 25 residential buildings to determine the mechanical properties of concrete such as compressive strength, modulus of elasticity, and Poisson’s ratio. Also, microstructural investigations were conducted on the concrete samples. The results showed that concrete samples had generally low strength and low deformation ability causing brittle failure of structures. When the compressive strengths of the concrete samples taken by the core drilling method were examined, it was determined that the results were between 4 MPa and 41 MPa, while the average compressive strength result was 16.7 MPa and the standard deviation was 8.6 MPa. Additionally, compressive strength results over 20 MPa were determined in 5 samples. The elasticity modules of the samples with compressive strength results above 15 MPa are higher than the value found in the equation given in TS500, while the others are lower. The elasticity modulus results were more compatible with the equation given in Eurocode. In addition, although there is no full agreement between the results obtained from Schmidt hammer measurements and the core drilling method results, the non-destructive method helps to find the weakest element on any floor. It can be concluded that there is a connection between the quality of concrete and the performance of buildings under severe earthquakes. Therefore, it is recommended to improve building codes, strengthen the inspection procedures, detail the quality control mechanisms, and sustain education/training programs to increase the resilience of the buildings in future earthquakes.