Bayesian-Based Multihazard Fragility Estimates for Tall Steel Structural Buildings with Vibration-Seismic Double Control Technique

Tall steel structures located in multihazard-prone regions should possess the ability to withstand the coupled effects of long-term wind-induced fatigue and intermittent seismic events throughout their service life. This study proposes a lifetime seismic fragility assessment framework for tall steel structures incorporating the wind vibration–seismic double control technique. The proposed framework explicitly incorporates wind-induced fatigue deterioration and epistemic uncertainty in seismic demand modeling, thereby establishing a closed-loop analytical procedure capable of capturing multihazard coupling effects. Within this framework, wind hazard is probabilistically characterized based on measured wind speed data and a Poisson process model, while cumulative wind-induced fatigue damage is quantified using probability-weighted analysis combined with a material degradation model. Taking buckling-restrained braces (BRBs) as the core components of the vibration-seismic double control system, nonlinear time-history analyses are conducted on a 30-story concentrically braced steel frame structure. Subsequently, a Bayesian updating approach is introduced to establish a time-dependent seismic fragility model. The results indicate that BRBs exhibit excellent double control performance under both wind and seismic excitations, particularly in mitigating the accumulation of wind-induced fatigue damage. The proposed analytical framework can effectively capture the progressive evolution of structural risk, while the Bayesian updating approach significantly constrains epistemic uncertainty associated with model parameters and provides seismic fragility estimates with confidence intervals. These findings provide a systematic method and theoretical support for the lifetime seismic resilience assessment and performance-based design of tall steel structures under multihazard coupling effects.