PSI - Issue 77

Ercan Işik et al. / Procedia Structural Integrity 77 (2026) 465 – 474

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Ercan Işik et al./ Structural Integrity Procedia 00 (2026) 000 – 000

1. Introduction Concrete and reinforcement deficiencies in RC elements significantly impair structural integrity by altering load transfer mechanisms and accelerating the onset of brittle failure modes. The combined presence of these deficiencies not only reduces the deformation capacity of RC members but also triggers fracture mechanisms that compromise the global stability of the structural system. In this study, these deficiencies in RC elements affected by the 2023 Kahramanmaraş (Türkiye) earthquakes were investigated in detail both observationally and numerically. The different levels of damage, fracture or destruction in RC structures after earthquakes reveal the importance of the design and construction stages of the structural elements. Determining structural damage after each earthquake, which causes different levels of damage and destruction, is significant for the continuation of social life, the realistic determination of earthquake hazards in residential areas, and the development of codes regarding structures. Any damage data collected from here is very valuable in terms of earthquake and structural engineering. Damage assessments to be made after an earthquake are also used to reveal whether the structures are implemented according to earthquake-resistant structural design principles. Studies conducted after earthquakes in Türkiye clearly show that insufficient longitudinal and transverse reinforcement in structural elements, as well as the use of low-strength concrete, are amon g the main causes of damage (Sezen et al., 2003; Doğangün, 2004; İnel et al., 2008; İlki and Celep, 2012; Çelebi et al., 2013; Işık, 2014; Bayraktar et al., 2015; Çağlar et al., 2020; Yakut et al., 2021). It has been observed that the inadequacy of transverse reinforcement in RC structural elements cannot withstand the shear forces that occur during an earthquake, which causes damage at different levels. These studies compare the conditions in the earthquake codes of different years but do not include any structural analysis (Öztürk et al., 2023; Akar vd., 2024; Işık et al., 2025; Sezgin et al., 2024). While prior studies have identified such deficiencies, few have combined in-situ photographic evidence with numerical simulations to quantify the effect of specific parameters on shear force capacity and ductility. As a result of field observations made by the authors in the provinces affected by these earthquakes, damages caused by insufficient transverse reinforcement in RC columns were evaluated. For this purpose, the damages caused by different transverse conditions were evaluated for columns. In the numerical analyses performed using static pushover analyses, transverse reinforcement diameter, spacing, material type, low-strength concrete, use of special earthquake crossties in columns, transverse and longitudinal reinforcement material differences, and bending angles of transverse reinforcement were selected as variables. To reveal the effect of low-strength concrete, structural analyses were also performed for C8/10 concrete. The difference between the study and other studies is that the damages caused by transverse reinforcement in columns were examined in much more detail, and these were based on structural analyses. The study bridges the gap between observational seismology, earthquake engineering practice, and code development, offering an evidence-based pathway for improving RC structural integrity. 2. Damages Caused by Transverse Reinforcement in Columns Insufficient transverse reinforcements in both columns and beams, as well as at their joints, have hindered the fulfilment of the expected functions of these reinforcements. The rules regarding the use of reinforcements in columns, as specified in the last two earthquake regulations used in Türkiye, are illustrated in Figure 1.

Fig. 1. Transverse reinforcement rules for columns in the last two codes (TSDC-2007; TBEC-2018).