Seismic Response and Design Implications of Single-Storey Steel Cantilever Structures: Evidence from the 2023 Kahramanmaraş Earthquake

The 2023 Kahramanmaraş earthquake sequence n Türkiye generated ground motions that locally exceeded the design seismic action prescribed by national codes, highlighting uncertainties regarding the seismic reliability of different structural systems. While multi-storey steel frames are extensively addressed in seismic design standards, significantly less attention has been devoted to single-storey cantilever steel structures, where plasticity is typically concentrated at column bases and structural redundancy is limited. This study investigates the seismic response of a single-storey steel cantilever structure located in Antakya, which survived the earthquake without collapse despite experiencing high seismic demand. The research combines field observations, modal analysis, response spectrum analysis (RSA), and nonlinear dynamic analyses (DNA) using recorded strong motion accelerograms from nearby seismic stations. Modelling assumptions, input motions, and performance criteria are explicitly defined to ensure methodological transparency. The results indicate that the observed structural survival can be attributed to controlled plastic hinging at the column bases, adequate restraint against column instability, and limited but stable energy dissipation capacity. Nonlinear analyses demonstrate a reduction of effective seismic demand by approximately 2,8 times compared to the elastic response, while second-order effects were shown to be non-negligible. Based on the analytical findings, rational behaviour factor q and displacement factor qd are proposed for the design of steel cantilever systems within the framework of Eurocode 8. The study contributes to the understanding of the seismic performance of these systems and provides design implications relevant to seismic-resistant structural engineering practice in regions of high seismic hazard.