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Robustness Analysis of Structures in Post-Earthquake Scenarios Considering Multiple Hazards
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Recent earthquakes have highlighted that the consideration of isolated seismic events, although necessary, may not be sufficient to prevent building collapse. In fact, the occurrence of a large number of aftershocks with significant intensity, as well as the occurrence of tsunamis, fires, and explosions, poses a safety threat that has not been addressed properly in the design and assessment of building structures over the last decade. Although research has been developed in order to evaluate the impact of multiple and/or cascading hazards in structural safety and economical losses, there is no established framework to perform such analysis. In addition, the available numerical tools lack a unified implementation in a widely used software in order to allow for the development of large numerical simulations involving these hazard events.
This work proposes a probabilistic framework for quantifying the robustness of structures considering the occurrence of a major earthquake (mainshock) and the subsequent cascading hazard events, namely fire and aftershocks. These events can significantly increase the probability of collapse of buildings, especially for structures that are damaged during the mainshock. In order to assess the structural performance under post-earthquake hazards, it is of paramount importance to accurately simulate the damage attained during the earthquake, which is strongly correlated to the residual structural capacity to withstand cascading events. In this context, the influence of ground motion characteristics, namely ground motion duration, has been identified as one of the parameters that may induce significant bias on damage patterns associated with the mainshock. Thus, ground motion duration influence on structural damage is analyzed in this work.
Steel moment resisting frame buildings designed according to pre-Northridge codes are
analyzed using the proposed framework. These buildings are representative of the design practice in the US and Europe for decades, and the conclusions of this work can be significant in the assessment/retrofit of thousands of buildings. Fragility curves and reliabilitybased robustness measures are obtained using the proposed framework. The fragility curve parameters obtained herein can be used in the development of future probabilistic-based studies considering post-earthquake hazards. The results highlight the importance of the post-earthquake hazard events in the structural safety assessment. Further work is needed in order to better characterize these hazards as to include them in the code-based design and assessment methodologies.
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Aftershocks Fire Non-linear dynamic analysis Reliability Robustness Seismic analysis