Seismic performance of RC staircases in the 2023 Kahramanmaraş earthquakes: Field observation, damage patterns and evacuation risk

Abstract This study investigates the damage patterns, failure mechanisms, and evacuation risks of reinforced-concrete staircases during the 2023 Kahramanmaraş earthquakes in Türkiye. Despite being crucial for safe evacuation and rescue operations, staircases are frequently overlooked in post-earthquake assessments. Field data from 91 buildings were collected and analyzed to understand staircase response to severe shaking and the risks posed to occupants. The results show that staircases with rigid connections acted as unintended diagonal braces, attracting seismic forces that caused shear failures, cracking, and sometimes collapse. These failures delayed evacuation and made escape routes hazardous. The Evacuation Difficulty Score (EDS), a novel logistic score that combines building height and staircase damage severity, is introduced in the study to quantify this risk. Analysis indicates that 25.3% of buildings reached critical EDS levels. Staircase vulnerabilities proved systemic rather than confined to obsolete design codes, with failures observed in both older and newer buildings. Three recurring patterns were identified: cracking in tall modern buildings, functionally risky medium damage in post-2000 mid-rises, and brittle failures in older stock. Code comparisons highlighted a regulatory gap, as TBEC 2018 and Eurocode 8 lack drift-compatible stair provisions, unlike ASCE 7–16. Overall, staircase safety is not only a structural problem but also a life-safety priority. It requires a proactive approach that includes needing drift-accommodating designs in new construction, retrofitting high-risk structures, and implementing EDS for screening.