Introducing Energy-Based Seismic and Flood Demand (EBSFD) for Multi-Hazard Vulnerability Analysis of Buildings

: Understanding energy dissipation mechanisms in buildings subjected to multiple hazards, such as earthquakes and floods, remains a critical yet underexplored area in structural engineering research. Current studies predominantly focus on single-hazard scenarios, leaving significant gaps in the assessment of structural performance under combined loading conditions. To address this gap, this paper presents an innovative framework termed energy-based seismic and flood demand (EBSFD) to evaluate the response of steel special moment-resisting frame (SMRF) buildings exposed to sequence-hazards. The study examines three distinct building configurations: 2-, 8-, and 20-storey structures, to analyse the impact of earthquakes and floods. Initially, computational fluid dynamics (CFD) simulations are employed to create three-dimensional (3D) models of the buildings, facilitating the determination of hydrodynamic load values exerted by floodwaters. Subsequently, nonlinear time-history analyses (NLTHA) are performed using these 3D models, incorporating a sequential hazard approach that considers both seismic and flood events. The analysis integrates four different flood levels with thirteen seismic hazard levels to assess the structural vulnerability under these intricate loading conditions. The distribution of EBSFD is examined in two contexts: loading from earthquakes alone and loading from the combined effects of earthquakes and floods (sequence-hazards). Findings indicate that floodwaters considerably increase the energy demands on the structures, with higher flood levels correlating with elevated demands. Notably, the upstream beams and columns are subjected to the most significant energy demands due to their direct interaction with hydrodynamic forces. Furthermore, the research underscores the predominant role of hysteretic energy in multi-hazard scenarios compared to damping energy, with columns being more effective in dissipating hysteretic energy than beams. This finding is particularly valuable for engineers seeking to understand the degradation of structural components over time when subjected to multi-hazard scenarios.