Recent researches focused on developing robust blast load mitigation systems due to the threats of terrorist attacks.One of the main embraced strategies is the structural systems that use mitigation techniques.They ar...Recent researches focused on developing robust blast load mitigation systems due to the threats of terrorist attacks.One of the main embraced strategies is the structural systems that use mitigation techniques.They are developed from a combination of structural elements and described herein as conventional systems.Among the promising techniques is that redirect the waves propagation through hollow tubes.The blast wave propagation through tubes provides an efficient system since it combines many blast wave phenomena,such as reflection,diffraction,and interaction.In this research,a novel blast load mitigation system,employed as a protection fence,is developed using a technique similar to the technique of the bent tube in manipulating the shock-wave.The relative performance of the novel system to the conventional system is evaluated based on mitigation percent criteria.Performances of both systems are calculated through numerical simulation.The proposed novel system proved to satisfy high performance in mitigating the generated blast waves from charges weight up to 500 kg TNT at relatively small standoff distances(5 m and 8 m).It mitigates at least 94%of the blast waves,which means that only 6%of that blast impulse is considered as the applied load on the targeted structure.展开更多
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
文摘Recent researches focused on developing robust blast load mitigation systems due to the threats of terrorist attacks.One of the main embraced strategies is the structural systems that use mitigation techniques.They are developed from a combination of structural elements and described herein as conventional systems.Among the promising techniques is that redirect the waves propagation through hollow tubes.The blast wave propagation through tubes provides an efficient system since it combines many blast wave phenomena,such as reflection,diffraction,and interaction.In this research,a novel blast load mitigation system,employed as a protection fence,is developed using a technique similar to the technique of the bent tube in manipulating the shock-wave.The relative performance of the novel system to the conventional system is evaluated based on mitigation percent criteria.Performances of both systems are calculated through numerical simulation.The proposed novel system proved to satisfy high performance in mitigating the generated blast waves from charges weight up to 500 kg TNT at relatively small standoff distances(5 m and 8 m).It mitigates at least 94%of the blast waves,which means that only 6%of that blast impulse is considered as the applied load on the targeted structure.
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.
