PSI - Issue 78

Yavuz Yadim et al. / Procedia Structural Integrity 78 (2026) 1895–1902

1899

initiated a partial collapse. Additionally, soft- or weak-storey formations, often due to open ground floors or irregular stiffness distribution, severely reduced inter-storey drift capacity. These deficiencies frequently coexisted within the same structure, compounding the severity and speed of the collapse.

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Fig. 3. (a) Shear damage at RC structural wall, (b) short column damage due to infill failure, and (c) short column failure.

Proper development and lap-splice lengths are essential for transferring stresses between the reinforcing steel and concrete and between the overlapping steel bars. If these lengths are insufficient, bond failure can occur, causing steel to slip within the concrete. In such cases, the reinforcement cannot reach its yield capacity, preventing concrete members from developing the intended flexural strength, stiffness, and ductility. Similar issues arise from inadequate lap-splice lengths between overlapping bars, which compromise structural continuity. During past earthquakes, bond failure at beam-column joints has led to widespread damage and the collapse of RC buildings. Notably, many failures were traced to insufficient development or lap-splice lengths within critical joint regions. Although Turkish seismic codes have mandated transverse reinforcement (stirrups) in beam-column joints since 1975, numerous buildings constructed before 2000 lacked adequate confinement in these regions. Consequently, the joints often failed prematurely, before beams and columns could achieve their designed flexural capacities. This premature joint failure undermined the stability of the entire structural system. Fig. 3 illustrates typical examples of such joint damage, including crushed concrete in the core region and buckled or slipped reinforcement resulting from poor detailing and inadequate confinement.

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Fig. 4. Samples of typical storey failure mechanisms in reinforced concrete (RC) frame buildings with several possible failure mechanisms: (a) strong beam-weak column, (b) axial or sehar failures due to low concrete strength, and (c) weak storey or short columns at ground level.

The use of materials with inadequate strength and ductility has been a persistent issue in Turkish construction practice, leading to devastating consequences during seismic events. This problem stems from various factors, including cost-cutting measures, a lack of proper building code enforcement, and insufficient knowledge of seismic resistant design principles. Buildings constructed with substandard materials are more susceptible to structural failure, collapse, and severe damage during earthquakes, thereby putting occupants at significant risk (Fig. 4).