Structural performance analysis of a retrofitted school building collapsed in Kahramanmaras earthquakes and evaluation of applied retrofitting methods

Abstract

On February 6, 2023, the Kahramanmaraş-centered earthquakes caused significant loss of life and extensive structural damage. These events have considerably increased research attention, especially on the seismic performance of retrofitted buildings. This study investigates a school building that was retrofitted in 2020 through the in-plane insertion of reinforced concrete shear walls but collapsed during the 2023 earthquakes. It is a significant case, as it is the only retrofitted building that collapsed according to official records. A comprehensive dataset was collected, comprising retrofitting plans, structural drawings, material and soil properties, and structural analysis reports. Finite element models of the retrofitted and non-retrofitted structures were developed in ETABS, and nonlinear pushover and time history analyses were performed. Pushover analyses assessed the retrofitting’s engineering suitability, while time-history analyses investigated the collapse mechanisms and overall seismic response. Results were compared in terms of story displacement, drift, forces, acceleration, energy components, and structural performance. Pushover analyses demonstrated up to an 80.6% reduction in both story displacements and drift ratios after retrofitting. However, damage levels in some columns increased, and improvements at upper stories remained limited. Time history analyses revealed reductions in displacement and drift demands of up to 89%, confirming overall performance gains. Stiffness increase caused substantial rises in story accelerations (up to 1600%) and shear forces (up to 70%), particularly in upper floors. These findings indicate that performance limitations stem from both design-related and construction-phase deficiencies. Therefore, future retrofitting strategies should adopt a holistic approach, integrating balanced stiffness distribution, optimized shear wall layout, precise connection detailing, and strict construction quality control.