## 4 Analysis of Heavily and Moderately Damaged Structure Materials in the Elbistan Region
### Equipment Condition  
Given the widespread use of lower-strength flat bars (i.e., those with 220 MPa instead of 420 MPa yield strength) as transverse reinforcement in the structures analyzed, the brittle failure modes of their RC vertical load-bearing members and joints further reduced their spherical ductility capacity. As a result, their ductility capacity implied by the default response modulation factor, typically taken as 4-8, may not have been available (Figure 11a,b and in circle detailed). Further, this study found that mild steel reinforcement was used in most of the structures, while hooks were used for pressure reinforcement. However, the starter bars of the structures were not long enough at the lower ends of their columns. Reinforcement corrosion was also observed (Figure 11c and in circle detailed). Although lap joint flaws were recommended in the pre-2018 regulation, longitudinal reinforcement in the middle region of building columns is still allowed to be provided in their end regions. Overlapping longitudinal reinforcing bars are commonly used in  
Figure 11: Incorrect steel rebar preferences. Figure 10: Non-destructive experimental test results. construction in Turkey. This leads to earthquake forces causing extreme bending moments in structures that use such bars. Longitudinal reinforcements are exposed to high impacts due to tensile and compressive forces. For this reason, tensile continuity must be provided at the reinforcement ends of columns. During earthquakes, force transmission is not fully realized. After the Kahramanmaras earthquake, heavy damage was observed in many buildings in the impact zone. The inadequacy of these buildings' reinforcement lap joints resulted in the buildings having a lack of uniform longitudinal bars and widely spaced transverse reinforcements due to there being a lack of sufficient expansion length. Overlap joints were also encountered in building lengths with insufficient stirrup spacing and development (Figure 9). Further, transverse reinforcement details play a crucial role in the seismic performance of reinforced concrete buildings. Reinforced concrete members with an inadequate length and improper hook angles can lead to shear damage and instability in columns before they reach their bending capacity. The insufficient closure of stirrups in columns or a lack of confinement with 90\({}^{\circ}\) hooked reinforcement can cause explosions. Similar problems have been observed in buildings damaged by earthquakes in Turkey in recent years. However, the 1975 TEC, the 1997 TEC, and the 2007 TEC specify that side reinforcement spacing should not exceed 10 cm. For $420 and $220 stirrups with 135\({}^{\circ}\) hooks at both ends, their linear length should be at least 10 cm, leaving a minimum linear length of 8 cm. Nevertheless, most structures in Kahramanmaras exhibited insufficient stirrup spacing and errors in their hook lengths and angles (Figure 12). Other Types of Damage in Buildings Heavily and Moderately Damaged by the Elbistan, Kahramanmaras, Earthquake  
Previous studies conducted in earthquake zones have documented the use of cheap workmanship and poor-quality materials [61]. Such investigations have shown that the earthquake regulations in these zones were not followed [62; 63]. In this study, the material quality of heavily and moderately damaged structures was investigated, and it was found that this damage did not depend only on the quality of the material used. Various types of damage were observed following the earthquake. For instance, damage caused by adjacent structures was extremely severe. The term \"structural impact\" refers to lateral collisions between adjacent buildings during earthquakes (as shown in Figure 10). Even though it is a requirement in the earthquake code, most neighboring buildings in Turkey do not have dilatation, which leads to an impact effect that causes damage (Figure 10b). Further, discrepancies in floor heights between adjacent buildings especially exacerbate the extent of damage.