The nonductile reinforced concrete building(NDRCB)stock-typically,pre-1974 structures in the U.S.-is a well-known high-risk group for seismic hazards.Prior studies indicate that there are approximately 1500 NDRCBs in ...The nonductile reinforced concrete building(NDRCB)stock-typically,pre-1974 structures in the U.S.-is a well-known high-risk group for seismic hazards.Prior studies indicate that there are approximately 1500 NDRCBs in Los Angeles.Through various ordinances,the owners are currently required to choose between demolition and,when appropriate,seismic retrofitting.Because fulfilling these ordinances will take decades,the potential risk of major losses will persist.In this study,a method for automated development of structural analysis models and damage fragilities for non-ductile moment-resisting frames is established.This capability enables seismic risk assessment at a regional scale using relatively limited building metadata and the era-specific seismic design code.The approach is used first to develop archetypal models in OpenSees,verified through static pushover and nonlinear time-history analyses against prior detailed studies.Fragility curves for discrete damage states are developed through a probabilistic seismic demand model.Additional investigations are carried out to consider the influence of soil-structural interaction effects and to determine the most suitable seismic intensity measures to quantify the seismic damage levels of NDRCB frames.The sensitivity of the proposed modeling method to variations/uncertainties in building configurations and properties is also examined through parametric studies.The method is limited to a particular subcategory of NDRBCs-namely,moment-resisting frames-but extensions to other types appear straightforward.展开更多
Damage from recent earthquakes has shown that substandard bridges are particularly vulnerable to strong ground motions being the weakest components of a road network.Structural and foundation damages in bridges lead t...Damage from recent earthquakes has shown that substandard bridges are particularly vulnerable to strong ground motions being the weakest components of a road network.Structural and foundation damages in bridges lead to a significant loss related to both repair process and a prolonged traffic disruption, which in turn results in large indirect loss in the affected area. Along these lines, the estimation of the overall loss related to earthquake-induced damage in highway bridges and overpasses must be based on a wider network analysis rather than on a single structural assessment. Key concept in such a comprehensive loss estimation procedure is the network resilience, expressing the extent of both direct and indirect loss, as well as the system's ability to quickly recover its preearthquake state. In this paper, a recently developed framework for assessing the loss and resilience associated with seismic impact on the structural and geotechnical components of a road network, as well as the relevant software developed are extended to further consider the implications of post-earthquake traffic demand variation. Moreover, a sensitivity analysis is conducted for a case study network to investigate the impact of traffic demand variation after a major earthquake event and the subsequent trip cancelations on the time-variant, cumulative cost at a network level. The results clearly highlight that not only the seismic resilience of a highway network should be assessed in a holistic manner coupling seismic hazard, structural and traffic analysis, but the latter shall include realistic scenarios with respect to the potential variation of origin-destination demand after the earthquake and during the recovery period.展开更多
文摘The nonductile reinforced concrete building(NDRCB)stock-typically,pre-1974 structures in the U.S.-is a well-known high-risk group for seismic hazards.Prior studies indicate that there are approximately 1500 NDRCBs in Los Angeles.Through various ordinances,the owners are currently required to choose between demolition and,when appropriate,seismic retrofitting.Because fulfilling these ordinances will take decades,the potential risk of major losses will persist.In this study,a method for automated development of structural analysis models and damage fragilities for non-ductile moment-resisting frames is established.This capability enables seismic risk assessment at a regional scale using relatively limited building metadata and the era-specific seismic design code.The approach is used first to develop archetypal models in OpenSees,verified through static pushover and nonlinear time-history analyses against prior detailed studies.Fragility curves for discrete damage states are developed through a probabilistic seismic demand model.Additional investigations are carried out to consider the influence of soil-structural interaction effects and to determine the most suitable seismic intensity measures to quantify the seismic damage levels of NDRCB frames.The sensitivity of the proposed modeling method to variations/uncertainties in building configurations and properties is also examined through parametric studies.The method is limited to a particular subcategory of NDRBCs-namely,moment-resisting frames-but extensions to other types appear straightforward.
基金funded by the National Strategic Reference Framework (NSRF) of Greece-Research Funding Program: Excellence Ⅱ: Reinforcement of the interdisciplinary and/or interinstitutional research and innovation under the grant real-time seismic risk(RETIS-Risk,2013-2015)
文摘Damage from recent earthquakes has shown that substandard bridges are particularly vulnerable to strong ground motions being the weakest components of a road network.Structural and foundation damages in bridges lead to a significant loss related to both repair process and a prolonged traffic disruption, which in turn results in large indirect loss in the affected area. Along these lines, the estimation of the overall loss related to earthquake-induced damage in highway bridges and overpasses must be based on a wider network analysis rather than on a single structural assessment. Key concept in such a comprehensive loss estimation procedure is the network resilience, expressing the extent of both direct and indirect loss, as well as the system's ability to quickly recover its preearthquake state. In this paper, a recently developed framework for assessing the loss and resilience associated with seismic impact on the structural and geotechnical components of a road network, as well as the relevant software developed are extended to further consider the implications of post-earthquake traffic demand variation. Moreover, a sensitivity analysis is conducted for a case study network to investigate the impact of traffic demand variation after a major earthquake event and the subsequent trip cancelations on the time-variant, cumulative cost at a network level. The results clearly highlight that not only the seismic resilience of a highway network should be assessed in a holistic manner coupling seismic hazard, structural and traffic analysis, but the latter shall include realistic scenarios with respect to the potential variation of origin-destination demand after the earthquake and during the recovery period.
