## 6 Findings and Discussion  
Through examining the damage status of buildings impacted by the Kahramanmaras earthquakes, this study observed that similar damage occurred in previous earthquakes. The damage inflicted by the Kahramanmaras earthquakes on post-2000 structures, in particular, was quite notable. When analyzing heavily and moderately damaged structures, the most apparent issues found were the subpar quality of the materials used and the incorrect design of their supports. In order to investigate the material quality of the analyzed buildings, both destructive and non-destructive experiments were conducted. Through these methods, this study found a linear relationship between the compressive strength of the obtained concrete samples and the pressure test data (Figure 17a-c). Figure 16: Examples of beam and column damage. Figure 17: Experimental Test Results. The experimental data were compared with respect to the codes, damage conditions, and construction periods of the buildings analyzed. Unfortunately, no strength values were able to be obtained from the core samples taken from two pre-2000, heavily damaged structures, as the samples began to disintegrate while they were being obtained; their concrete had no adherence left. UPV and Schmidt values were obtained from a total of 20 buildings. For the pre-2000, heavily damaged structures, these values were in a similar range: their Schmidt values remained between 12 and 15, and their concrete strength remained around 4 MPa. For this first group of buildings, we can state that they were heavily damaged due to the material used for their construction; this material did not exhibit adequate strength properties. Conversely, the experimental results for the post-2000, heavily damaged buildings were very different. Here, it was determined that the damage that these structures experienced was not just caused by the quality of their construction material. Just like within the group of pre-2000, moderately damaged structures, the values obtained for the post-2000, moderately damaged structures were similar to one another. The strength of these post-2000, moderately damaged structures, however, was below the established standard. Their concrete strength values remained below 15 MPa, while their Schmidt values were around 30 to 35. These Schmidt and UPV results assisted us in determining the material quality of the studied buildings in a non-destructive way. The damage present made it difficult to obtain samples from the structures due to their large dimensions (Figure 18). In addition to the quality of the concrete, the reinforcements used in the analyzed reinforced concrete structures seemed to have been selected in accordance with the regulations for new buildings, but problems were observed in their fastening and frequency of placement. The main reason for building collapse was found to be the wide spacing of stirrups, which caused shear fractures, as well as the buckling of longitudinal rebars and the poor containment of core concrete. The stirrups used in these cases were not effective due to the insufficient length of their embedded hooks. Additionally, the insufficient cross-sectional area of these buildings' columns caused damage. Severe damage to or the collapse of buildings was also caused by inadequate longitudinal reinforcement (less than 1.0%), short lap joints, and incorrect end-hook angles in main bars. The use of low-quality concrete in the affected area further compromised the seismic performance of the reinforced concrete buildings. Existing damage was also observed in some buildings, which can be attributed to their poor quality and the fact that such structures were not affected by weak ground or earthquake amplification. In this study, some of the problems documented were encountered during field observations. For instance, it was found that there were manufacturing problems in the strengthening of existing reinforced concrete buildings. In particular, it was observed  
Figure 18: Experimental comparison of material types.