Rethinking non-structural vulnerability of EC8-compliant steel buildings with glass façades

Non-structural components account for a significant share of building construction costs and strongly influence seismic performance and post-earthquake losses. Eurocode 8 Part 1 (EC8–1) recognises their importance, particularly in buildings with steel moment-resisting frames (SMRFs), yet provides limited guidance for the seismic assessment of acceleration-sensitive components (ASCs), such as point-fixed glass façade systems (PFGFSs). This study investigates the seismic vulnerability of structural components and non-structural components, including drift-sensitive components (DSCs) and ASCs, in mid-rise European SMRF buildings designed in accordance with EC8–1. Three index buildings with different inter-storey drift ratio (IDR) limits were analysed using 2250 nonlinear time-history simulations to derive fragility and vulnerability functions. A dedicated graphical user interface (GUI) toolkit was developed to support the systematic evaluation of structural and non-structural vulnerability. The results demonstrate a clear drift–acceleration trade-off: adopting the minimum IDR required for serviceability significantly reduces vulnerability of the structural system and DSCs, but leads to a marked increase in peak floor accelerations and vulnerability of ASCs. A detailed case study on PFGFSs, based on a validated three-dimensional numerical model and 15 pairs of recorded ground motions, shows that façade systems experience substantially higher IDR and peak floor acceleration than the main structure, with demands at roof level up to approximately 80% higher. The proposed fragility and vulnerability functions provide practical tools for seismic risk assessment and highlight the need to revise existing fragility thresholds and design provisions for acceleration-sensitive non-structural components in future European seismic codes.