Fires associated with vehicles have the potential to impact on life safety and property protection. The fire severity characteristics of single passenger vehicle fires are presented in this paper by the total energy released, peak rate of heat release and the time to peak rate of heat release using experimental data collated from the literature. Risk-based fire design can be supported by data presented in a statistical form such that passenger vehicles are categorized by their curb weight and probability distribution curves are obtained for each fire severity characteristic. Analysis of the data shows that the total energy released and the time to peak rate of heat release are generally shown to exhibit an increasing trend with curb weight.
a b s t r a c tThe time-equivalence method is one way to determine the appropriate fire severity in buildings. One of the input parameters required is the fire load energy density (FLED) and in a deterministic design this is taken to be a fixed value. This paper illustrates the use of a simple Monte Carlo tool that accounts for statistical variations in car energy content as a function of vehicle size to determine probabilistic FLED values for a risk-based calculation approach to the design of car parking buildings. The paper briefly discusses FLED values for car parking buildings that can be found in the literature and results from the Monte Carlo tool suggest that 260 MJ/m 2 could be used as an appropriate design value in lieu of using a probabilistic approach.
Introduction
BackgroundCurrently there is debate in New Zealand regarding the design of steel structure car parks and the use of the time-equivalence calculations to determine appropriate severity for these buildings. Equations for calculating time-equivalence can be found in the New Zealand verification method C/VM2 [1]. These are based on equations from the Eurocode [2], but with an expanded set of factors to allow for adequate consideration of the contributions of different room lining materials [3].In order to calculate fire severity using a time-equivalence method one of the parameters needed is the fire load energy density (FLED) which is the sum of all the energy available for release when the combustible materials are burned, divided by the total floor area of the compartment. The available energy content can be distinguished into permanent, variable, protected and unprotected loads [4]. Typically an 80th percentile variable fire load is used as a design value when using data from fire load surveys [4,5]. For a car parking building the variable load is essentially the vehicles and the calculation of FLED incorporates any floor areas used for vehicle lanes and ramps, pedestrian walkways, etc.Typically time-equivalence calculations are carried out deterministically with fixed values assigned for FLED, compartment geometry, ventilation conditions, lining materials and the structural material being used for the design. The process considers that the compartment is uniformly heated throughout the fire exposure and for a car park fire scenario this effectively assumes the building is densely populated with vehicles and that they are on fire simultaneously. However in a densely populated car park it is possible that the fire will travel from vehicle to vehicle rather than assuming all are burning http://dx.simultaneously. Recent work on travelling fires by has introduced a new methodology using travelling fires to produce more realistic fire scenarios in large, open-plan compartments for structural fire design. SternGottfried et al. examined the impact of FLED on their estimation of the peak structural member temperature. Their results show that local concentrations of dense fuel loads produce long-duration fires and have a significant effect on struct...
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