12.07.2015 Views

Report - PEER - University of California, Berkeley

Report - PEER - University of California, Berkeley

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major drawback <strong>of</strong> this method when applied to bridge-level decisions is a largemodel error. This results in low confidence (large dispersion) in predicting the medianrelationship between engineering response and earthquake intensity. This uncertaintyis propagated through the subsequent models and results in a significant lack <strong>of</strong>confidence in the damage and decision fragilities.Figure 4. Bridge load-carrying capacity loss model.Figure 5. Decision fragility surface generated using the direct method.Other shortcomings are also apparent: there is a large jump in probabilities <strong>of</strong>exceedance a DV for small IM values. This is not realistic, as it is expected thatdamage would start to accumulate only at higher earthquake intensities, not during theelastic response <strong>of</strong> the bridge. Nevertheless, as these bridge-level models are derivedby direct application <strong>of</strong> the <strong>PEER</strong> framework, they are useful as benchmarks.60

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