The accidental release of a flammable gas on a road can result in a vapour cloud explosion (VCE). Such VCEs generate a blast wave that propagates away from the explosion, potentially damaging nearby structures. The TN...The accidental release of a flammable gas on a road can result in a vapour cloud explosion (VCE). Such VCEs generate a blast wave that propagates away from the explosion, potentially damaging nearby structures. The TNO Multi-Energy Method is commonly used for a simplified estimate of the blast load resulting from a VCE. The method characterises the severity and duration of the blast wave using a case-specific strength class and combustion energy (which the method relates to the gas volume of the equivalent blast source). However, no specific guidelines for estimating the strength class in urban roads or related settings (such as carparks) are currently available in the literature. This makes implementing the method in such scenarios challenging and imprecise. The authors’ work used computational fluid dynamics (CFD) to evaluate multiple gas explosion scenarios and proposed recommendations for determining the strength class and gas volume at the blast source. These scenarios comprised a group of vehicles engulfed by a stoichiometric propane-air cloud. It was concluded that the strength class could be reasonably estimated based on the number of vehicles in the transverse direction. Furthermore, the guidance for estimating the gas volume at the equivalent blast source was based on the critical gas volume, after which no further enhancement of overpressure was obtained. The recommendations were implemented in several scenarios and compared with corresponding CFD analyses. The results showed very good agreement for predicting impulse. Predicting overpressure was affected by the inherent asymmetry of the scenarios, although it was possible to achieve acceptable and conservative results.展开更多
Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to ...Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to the materials,geometry,and resistance models,it may be difficult to predict which failure mode will prevail.This study analytically estimated the probability of premature flexural shear failure of slender RC one-way slabs subjected to blast loading considering such uncertainties and using the Monte Carlo(MC)method.The resistance models in Eurocode 2 were adopted.Specimens with and without shear reinforcement were analyzed.Bending failure was shown to be the most likely failure mode in the studied slabs.However,the probability of shear failure developing before bending failure was still relatively high,particularly for slabs without stirrups.To increase the confidence level concerning the preferred failure mechanism,the article proposes an overstrength factor to magnify the shear demand of the blast-loaded RC slab.Values of the overstrength factor for different target reliability levels were calculated.The study also found that the probability of premature shear failure increased with increasing amount of longitudinal reinforcement and decreasing slenderness.Likewise,greater impulse was found to enhance the risk for shear failure.展开更多
文摘The accidental release of a flammable gas on a road can result in a vapour cloud explosion (VCE). Such VCEs generate a blast wave that propagates away from the explosion, potentially damaging nearby structures. The TNO Multi-Energy Method is commonly used for a simplified estimate of the blast load resulting from a VCE. The method characterises the severity and duration of the blast wave using a case-specific strength class and combustion energy (which the method relates to the gas volume of the equivalent blast source). However, no specific guidelines for estimating the strength class in urban roads or related settings (such as carparks) are currently available in the literature. This makes implementing the method in such scenarios challenging and imprecise. The authors’ work used computational fluid dynamics (CFD) to evaluate multiple gas explosion scenarios and proposed recommendations for determining the strength class and gas volume at the blast source. These scenarios comprised a group of vehicles engulfed by a stoichiometric propane-air cloud. It was concluded that the strength class could be reasonably estimated based on the number of vehicles in the transverse direction. Furthermore, the guidance for estimating the gas volume at the equivalent blast source was based on the critical gas volume, after which no further enhancement of overpressure was obtained. The recommendations were implemented in several scenarios and compared with corresponding CFD analyses. The results showed very good agreement for predicting impulse. Predicting overpressure was affected by the inherent asymmetry of the scenarios, although it was possible to achieve acceptable and conservative results.
基金supported by Trafikverket(Swedish Transport Administration)Fortifikationsverket(Swedish Fortifications Agency)Myndigheten för samhällsskydd och beredskap(Swedish Civil Contingencies Agency).
文摘Blast-loaded reinforced concrete(RC)slabs should fail under a ductile bending mechanism enabling high energy absorption capacity.Hence,brittle shear failure must be avoided.However,due to the uncertainties related to the materials,geometry,and resistance models,it may be difficult to predict which failure mode will prevail.This study analytically estimated the probability of premature flexural shear failure of slender RC one-way slabs subjected to blast loading considering such uncertainties and using the Monte Carlo(MC)method.The resistance models in Eurocode 2 were adopted.Specimens with and without shear reinforcement were analyzed.Bending failure was shown to be the most likely failure mode in the studied slabs.However,the probability of shear failure developing before bending failure was still relatively high,particularly for slabs without stirrups.To increase the confidence level concerning the preferred failure mechanism,the article proposes an overstrength factor to magnify the shear demand of the blast-loaded RC slab.Values of the overstrength factor for different target reliability levels were calculated.The study also found that the probability of premature shear failure increased with increasing amount of longitudinal reinforcement and decreasing slenderness.Likewise,greater impulse was found to enhance the risk for shear failure.
