Seismic Fragility Assessment of Cable-Stayed Bridge Using Incremental Dynamic Analysis and Uniform Design Method

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The consideration of effective uncertainties is one of the important issues in seismic vulnerability assessment of structures. So in this paper, the combined method of IDA&UD-Based Fragility Assessment is proposed based on the uncertainties present in seismic fragility assessment procedure. We use Uniform Design (UD) method to produce reasonable random capacity models and Incremental Dynamic Analysis (IDA) method to produce probabilistic seismic demand model (PSDM). The fragility curve is obtained for components of the structure by applying these models on a cable - stayed bridge and defining the damage states. These curves indicate the probability of a component exceeding a damage state for an intensity measure of an earthquake. Then, using jointly probabilistic model, the fragility curve for the bridge system can exactly be determined from the components’ fragility curves. Finally, the fragility curves resulted from the proposed method are compared against the curves resulted from the simplified common method used in previous studies. This paper shows that: 1. Ramberg-Osgood relationship is an acceptable estimation of Cable-stayed Bridge’s probabilistic seismic demand model. 2. IDA method, in combination with UD method, can simultaneously consider the uncertainties in demand and capacity of the structure. 3. Compared to other methods, UD method reduces the calculations and has higher accuracy. 4. The proposed method can eliminate the relatively high conservativeness of instructions by conducting a reasonable approach.