A New Approach to Multi-Hazard Analysis

Journal of Structural Engineering

Recently, multi-hazards engineering has received more attention to analyzing the behavior of a system exposed to different types of hazards and to estimate the loss data from cascading events attributed to the primary hazard. In this paper, the principle of multi-hazards was investigated and a new methodology was developed to assess the total damage of structural elements caused by cascading hazards. For each hazard, a physical model is used to assess the conditional probability of exceeding a certain intensity level due to the occurrence of the previous hazard. The method was applied to a hospital located in California, US, subjected to the three cascading hazards (earthquake, blast, and fire). Non-linear time-history analyses were performed using seven ground motions scaled to five different earthquake levels and the seismic response of the structure was evaluated. The seismic input produces damage to the hospital's power supply (Liquid Propane Gas reservoir tank) which may cause a blast. The probability of explosion was estimated by taking into account the probabilities of fuel leakage, fuel concentration, and ignition. A set of nine blast intensity levels was considered in the analyses, corresponding to different quantities of fuel content inside the tank. Afterward, a fire hazard is generated following the explosion, whose intensity level was evaluated using the compartmental heat flux. The fire effects were modeled assuming an increment of temperature in the steel frames. The proposed multi-hazard approach can be used for both improving the structural safety and reducing the building life cycle costs to enhance in the end, the resilience of

Steel Construction, 2011

… Part Two(AIP …, 2008

It is desirable to verify the structural performance based on a multi-hazard approach, 8 taking into account the critical actions the structure in question could be subjected to 9 during its lifetime. This study presents a multi-hazard approach to calculation of the risk 10 associated with the limit state of collapse for a reinforced concrete (RC) structure 11 subject to both seismic and blast threats, using the de minimis risk level accepted in the 12 society as a point of reference. The annual risk of structural collapse can be calculated 13 taking into account both the collapse caused by an earthquake event and the blast-14 induced progressive collapse. Similar to the concept of seismic fragility, the blast 15 fragility can be defined as the probability of progressive collapse given a blast event has 16 taken place. The blast fragility can be calculated using a simulation procedure for 17 generating possible blast configurations. The event of progressive collapse in the 18 structure, for each blast configuration, can be identified by a Bernoulli indicator variable 19 which assumes the value of one in the case of progressive collapse and zero otherwise. 20

Applied Sciences

This paper proposes a hybrid multiscale approach to evaluate the fire performance of large multicompartment structures. A probabilistic network model is at the core of the proposed approach, whose inputs, namely the mean durations of the fire phases and fire transmission through the barriers between compartments (e.g., walls or ventilation ducts), are determined beforehand by a zone model, which is detailed in a companion paper and a one-dimensional computational fluid dynamics code. Next, a proof of concept is developed by applying the hybrid approach to different fire scenarios in a full-scale generic military corvette and a four-story office building. The simulation results highlight the strengths and limitations of the proposed approach. Regarding the latter, a field model is used to evaluate how the hybrid approach performs depending on the interaction between the entire building system and its ventilation and the fire. Finally, a statistical study is carried out to produce fir...

Nuclear Engineering and Design, 2019

The International Atomic Energy Agency emphasizes on the safety assessment of fires involved by the crash of a large commercial aircraft into a nuclear power plant. In the guideline, it requires that a total load of aviation fuel that causes damage to exterior plants' components should be included when performing the initial stages of the nuclear plant site evaluation process and over the entire lifetime of the plant operation. In this study, the effects of jet fuel and hydrogen-induced external explosion on a nuclear power plant was investigated and analyzed. A turbulence model based on Reynolds-averaged Navier-Stokes CFD solver, called FLACS, was used to determine the explosion parameters within the plant vicinity. The simulation results of key explosion parameters for butane explosion show a deflagrative overpressure of 0.27 bar and impulse load of 0.015 bar•s at some preselected position. An elevated local temperature of about 2030 K is recorded for this fuel. Hydrogen explosion causes a maximum overpressure of 0.37 bar, and a maximum positive pressure impulse load of 0.022 bar•s at the exterior walls of building structures. From the findings, it showed that building obstacles have a substantial influence on the evolution of fireball and overpressure propagation. The computed overpressure and impulsive loadings observed are capable of causing substantial structural damages and vulnerabilities. A significantly elevated flame temperature recorded would have a harmful effect on the safety function of structures, systems and components (SSCs) that are needed to execute reactor shutdown. The findings of this study may be used to revisit the safety evaluation of a nuclear power plant (NPP) site with regards to the risks and consequences associated with external explosion due to aircraft impact. It is also useful in designing the layout of the NPP and site placement of relevant items important to safety.

Fire Safety Journal, 1999

Real explosions in domestic structures (Rasbash and Stretch, Struct. Eng 1969;47;403}11) and industrial plants (Howard, Loss Prevention 1972;6;68}73) have been analyzed. De#agration dynamics are solved for enclosures of volumes of 130}8000 m for vent release overpressures in the range of 0}0.21 bar, and for di!erent inertia of covers over the venting spaces in the range 0}15 kg/m. From comparisons of the real explosion data with the modeling of pressuretime behavior during vented gaseous de#agrations according to an earlier lumped parameter theory values of the main parameter, a turbulence factor, , are obtained. The results suggest the combustion is highly turbulent for real conditions in domestic structures (turbulence factor *8 with discharge coe$cient "0.6) and especially in large-scale enclosures such as a plant, with internal obstacles (turbulence factor *17). On the basis of the devised e!ective turbulence factors (the ratio /) the design procedures for avoiding the development of excessive overpressures during de#agrations, in both domestic and industrial plant, can be improved.

Statyba, 2001

Fire Safety Journal, 2013

Fire and explosion are accidents which potentially can occur in oil and gas processing facilities. While fire and explosion could occur as a consequence of each other, most published work has assessed fire and explosion separately, ignoring interactions between the two phenomena.

2015

Community resilience to extreme events is an issue of increasing concern in our interconnected and urbanized societies. This work provides a framework to evaluate the response of a community of buildin gs to fire following earthquake, a potentially highly destructive cascading multi-hazard event. In a prev ious part of the work, a model has been developed to pre dict the probability of ignition in a building due to an earthquake. Given an ignition in a building, the pr obability of the structure exceeding certain limit states must be evaluated in order to quantify the expected damage loss. Adopting an approach similar to that used in seismic engineering, fragility functions can be developed for structures subjected to fire. The methodology is described here for a prototype nine- story steel frame building. In developing the fragi lity functions, uncertainties in the fire model, the hea t transfer model and the thermo-mechanical response are considered. In addition several fire scena...

Journal of Earthquake Engineering, 2015

A criterion for the estimation of losses of a structure exposed to several hazards is presented. It includes an approach to estimate the probability density function of the total damage that may be generated by the superposition of the effects of several simultaneous hazardous events that can be associated with a main primary event. It considers the probabilistic correlation of damage or failure of a structure due to the combined action of those simultaneous associated hazards. Finally, the intensities and times of occurrence of all relevant events of different natural origin that may significantly contribute to the risk for the structure of interest are taken into account, considering them as independent, with a negligible probability of producing simultaneous groups of significant associated hazardous events.