Structural material evaluation of 400 collapsed RC buildings after February 6, 2023 Kahramanmaraş double earthquakes in Türkiye

This article examines the structural material quality and code compliance of 400 collapsed reinforced-concrete (RC) buildings following the February 6, 2023 Kahramanmaraş double earthquakes in Türkiye. Based on field investigations across Kahramanmaraş, Adıyaman, Hatay and Gaziantep, it compiles building documentation and conducts detailed assessments of concrete and reinforcement properties, drawing on both laboratory testing and existing technical reports. The study aims to identify material-related contributors to collapse and to inform resilience strategies for RC building stocks in other earthquake-prone regions.

The findings indicate widespread material deficiencies that likely contributed to poor seismic performance, including low and non-homogeneous concrete strength, inappropriate aggregate selection and granulometry (notably large, smooth stream aggregates), poor workmanship and insufficient compaction. A substantial share of buildings exhibited compressive strengths below key thresholds, with evidence of variability between average and minimum strength values suggesting inconsistent mix design and construction practices. The analysis also documents mixed use of ribbed and non-ribbed reinforcement, especially in older buildings and in cases linked to illegal additions or unengineered modifications, alongside corrosion and compliance gaps in reinforcement standards.