Fragility Estimates for High-Rise Buildings with Outrigger Systems Under Seismic and Wind Loads

This paper proposes probabilistic demand models to assess fragilities for high-rise buildings with three types of outrigger systems under seismic and wind loads. Parameters of the structural model are determined based on the structural material and geometric conditions. Parameters of the excitation model are determined based on the hazard characterization that varies with the hazard type. This paper involves three types of hazards: high-frequency ground motions, near-fault ground motions, and stochastic wind loads. With the input information from the structural model and the excitation model, 3D finite element models are built and computed using ANSYS to obtain structural responses (output information). Based on a database with the input-output pair obtained, we formulate probabilistic demand models for high-rise buildings with three types of outrigger systems under three types of hazards. These probabilistic models are proposed to estimate three response quantities of interest, the maximum inter-story drift, the maximum top acceleration, and the maximum top displacement. They, therefore, include univariate, bivariate, and tri-variate models. The probabilistic demand models account for both aleatory and epistemic uncertainties and provide unbiased estimates. With a direct and parsimonious formula, they have high accuracy and are extremely convenient to be used in practical engineering. They are finally used to formulate fragility estimates with bounds for an example high-rise building with three types of outrigger systems under three types of hazards. The results indicate that damped outrigger systems can effectively reduce fragilities for high-rise buildings under three types of hazards.