1. Model uncertainty in a parametric fire curve approach : a stochastic correction factor for the compartment fire load densityFlorian Put, Andrea Lucherini, Bart Merci, Ruben Van Coile, 2024, izvirni znanstveni članek Povzetek: A commonly used approach to represent the thermal load in a compartment fire is the Eurocode Parametric Fire Curve (EPFC), which specifies gas temperatures (or rather adiabatic surface temperatures). Recognizing the significant deviations between real fires and the EPFC framework, the concept of model uncertainty is explored. This study does not aim to assess or improve the EPFC, but introduces a model uncertainty, allowing for reliability-based structural fire engineering (SFE). It presents a stochastic correction factor for the fire load density, based on the maximum temperature in steel sections. The focus is on the fire load density, but in general other parameters can be jointly taken into account as well. This correction factor considers protected and un- protected sections, incorporating variations in section factor and protection thickness. The findings reveal that the fire load density within the EPFC framework can be modified to better represent the severity of fire ex- periments. This approach ensures physical consistency of the obtained compartment gas temperatures, as opposed to alternative approaches for addressing the EPFC model uncertainty. While promising results are evident in this proof of concept, exploration for other types of structural elements and evaluation for structural systems is necessary before integration into design practices.
Ključne besede: structural fire engineering, compartment fires, fire load density, steel structures, reliability, probability of failure
Objavljeno v DiRROS: 17.04.2024; Ogledov: 71; Prenosov: 23
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2. Thermal characterisation of the cooling phase of post-flashover compartment firesAndrea Lucherini, Balša Jovanović, Jose L. Torero, Ruben Van Coile, Bart Merci, 2024, izvirni znanstveni članek Povzetek: The main characteristics of the cooling phase of post-flashover compartment fires are studied using a simplified first-principles heat transfer approach to establish key limitations of more traditional methodologies (e.g., Eurocode). To this purpose, the boundary conditions during cooling are analysed. To illustrate the importance of a first-principles approach, a detailed review of the literature is presented followed by the presentation of a simplified numerical model. The model is constructed to calculate first-order thermal conditions during the cooling phase. The model is not intended to provide a precise calculation method but rather baseline estimates that incorporate all key thermal inputs and outputs. First, the thermal boundary conditions in the heating phase are approximated with a single (gas) temperature and the Eurocode parametric fire curves, to provide a consistent initial condition for the cooling phase and to be able to compare the traditional approach to the first- principles approach. After fuel burnout, the compartment gases become optically thin and temperatures decay to ambient values, while the compartment solid elements slowly cool down. For simplicity, convective cooling of the compartment linings is estimated using a constant convective heat transfer coefficient and all linings surfaces are assumed to have the same temperature (no net radiative heat exchange). All structural elements are assumed to be thermally thick. While these simplifications introduce quantitative errors, they enable an analytical solution for transient heat conduction in a semi-infinite solid that captures all key heat transfer processes. Comparisons between the results obtained using both approaches highlight how, even when considering the same fire energy input, the thermal boundary conditions according to the Eurocode parametric fire curves lead to an increase energy accumulated in the solid after fuel burnout and a delay in the onset of cooling. This is not physically correct, and it may lead to misrepresentation of the impact of post-flashover fires on structural behaviour.
Ključne besede: cooling phase, fire decay, fire dynamics, compartment fires, structural fire engineering, fire safety
Objavljeno v DiRROS: 15.04.2024; Ogledov: 113; Prenosov: 57
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3. Thin-layer boilover of large-scale diesel pool fires at sub-atmospheric pressureJinlong Zhao, Qingyuan Zhang, Zhenqi Hu, Rongxue Kang, Grunde Jomaas, Rui Yang, 2024, izvirni znanstveni članek Povzetek: As thin-layer burning of fuels on water are often followed by thin-layer boilover fires, particularly during the firefighting process, an experimental and numerical study was undertaken to address key aspects of such fires, especially in plateau areas (i.e., sub-atmospheric pressure). In the thin-layer boilover experiments at sub-atmospheric pressure (69 kPa), diesel was used as the fuel in five circular steel trays (ranging from 0.4 m to 1.2 m in diameter) and a square steel tray (side length of 2.5 m). The burning process, and especially the continuous boilover stage, was presented and the corresponding boilover intensity, time to boilover onset and boilover time interval were measured and analyzed. The results show that the flame height increased sharply at the initial boilover, while this increasing range gradually became weak for the subsequent boilovers. The initial boilover intensity showed a linear dependency on the fuel layer thickness at the time of boilover, and the slope of the boilover intensity line decreased with increasing pan area. Eventually, the effect of pan area on boilover intensity became limit. Moreover, a predictive model for the boilover intensity was established based on dimensionless analysis. The initial boilover onset time under the sub-atmospheric pressure was delayed compared with that under atmospheric pressure. The corresponding predictive correlation (for 69 kPa) with different diameter and fuel thickness was developed based on the one-dimension two-layer conduction model. In the end, the boilover time interval decreased with the boilover times, closing to uninterrupted boilover eventually. This work enriches the thin-layer boilover behavior experimental data at sub-atmospheric pressure and provides guidance for the fuel storage safety.
Ključne besede: thin-layer boilover, boilover intensity, time to boilover onset, boilover time interval, sub-atmospheric fires
Objavljeno v DiRROS: 16.01.2024; Ogledov: 178; Prenosov: 39
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4. Experimental study of the burning behavior and key parameters of gasoline pool fires with different ullage heightsJinlong Zhao, Xinjiang Li, Zhenqi Hu, Rongxue Kang, Grunde Jomaas, 2023, izvirni znanstveni članek Povzetek: Pool fires with different ullage heights are a common type of fire accident. A series of gasoline pool fire ex- periments with two sizes (D = 40 cm, 60 cm) and six ullage heights (h = 0, 0.2D, 0.4D, 0.6D, 0.8D, 1.0D) are conducted. The burning process, axial temperature profile, radiative heat feedback, and burning rate are measured and analyzed. The result shows that the fuel vapor layer and the down-reaching flame layer are distinguished based on the axial temperature profile for the steady burning stage. Meanwhile, the down-reaching flame length (Ldown) increases more profoundly for large tank diameters under the same ullage height. Subse- quently, the dimensionless down-reaching flame length (Ldown* = Ldown/D) increases exponentially with the dimensionless ullage heights (h* = h/D). Finally, based on the classical burning rate model for the low ullage height and the heat transfer process from the flame to the fuel surface, a correlation with different ullage heights is established to calculate the burning rate, which is then validated against the experimental data in the paper and literature values. The results are of importance to understand the burning rate and the radiative heat feedback to the fuel surface for pool fires with different ullage heights.
Ključne besede: pool fires, ullage height, down-reaching flame, flame radiative heat feedback, burning rate correlation
Objavljeno v DiRROS: 08.01.2024; Ogledov: 173; Prenosov: 38
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5. Closing data gaps and paving the way for pan-European fire safety efforts : Terminology of fire statistical variablesMartina Manes, Ana Sauca, Mohamad El Houssami, Petra Andersson, Colin McIntyre, Richard Campbell, David Rush, Anja Hofmann, Peter Wagner, Sergei Sokolov, Mindel Leene, Margrethe Kobes, Dirk Oberhagemann, Nicola Rupp, Grunde Jomaas, Friedrich Grone, Eric Guillaume, 2023, izvirni znanstveni članek Povzetek: A well-defined terminology of fire-related variables is important for correct analyses and supporting knowledge-based decisions regarding the evaluation of building fires at the European level. After developing an overview of current practices for fire statistics in Part I, the terminology used and the data collected by the EU Member States and eight other countries regarding fire incidents, property damage and human losses were mapped to increase awareness of their practice and support a comprehensive assessment of several fire statistical datasets. A questionnaire was distributed to relevant authorities responsible for the collection, elaboration/analysis, and fire statistical data publications to define and select the essential variables for an appropriate fire assessment and fire incident description. Based on the results of the questionnaire able to identify the essential fire statistical variables and a detailed analysis of current definitions adopted in the fire statistics of the EU Member States and other countries, a common terminology is proposed to collect the necessary data in the EU Member States and obtain meaningful datasets based on standardised terms and definitions. The results will generate essential outputs to move towards harmonised fire statistics at the EU level and contribute to an appropriate analysis able to improve fire prevention and fire mitigation in building fires.
Ključne besede: fire statistics, fire incidents, building fires, fire statistical variables, terminology
Objavljeno v DiRROS: 13.11.2023; Ogledov: 298; Prenosov: 148
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6. Defining the fire decay and the cooling phase of post-flashover compartment firesAndrea Lucherini, Jose L. Torero, 2023, izvirni znanstveni članek Povzetek: The current research study discusses and characterises the fire decay and cooling phase of post-flashover compartment fires, as they are often mixed up despite their important heat transfer differences. The two pha- ses are defined according to the fire heat release rate time-history. The fire decay represents the phase in which the fire heat release rate decreases from the ventilation- or fuel-limited steady-state value of the fully-developed phase to fire extinguishment. This phase is highly influenced by the fuel characteristics, ranging from fast decays for hydrocarbon and liquid fuels to slow decays for charring cellulosic fuels (wood). Once the fuel is consumed, the compartment volume enters the cooling phase, where the cooling in the gas-phase and solid-phase happens with significantly different modes and characteristic times. The thermal boundary conditions at the structural elements are then defined according to physical characteristics and dynamics within the compartment. The research study also underlines how the existing performance-based methodologies lack explicit definitions of the decay and cooling phases and the corresponding thermal boundary conditions for the design of fire-safe struc- tural elements under realistic fire conditions.
Ključne besede: razpadanje ognja, hlajenje, izgorevanje, naravna izpostavljenost ognju, dinamika požara, požari v oddelkih, požarno inženirstvo, učinkovitost, požarna varnost, fire decay, cooling, burnout, natural fire exposure, fire dynamics, compartment fires, structural fire engineering, performance-based, fire safety
Objavljeno v DiRROS: 13.11.2023; Ogledov: 290; Prenosov: 138
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7. Hands-on guidelines for private woodlot owners in Slovenia, Latvia, Estonia, Sweden and Spain2021, slovar, enciklopedija, leksikon, priročnik, atlas, zemljevid Ključne besede: Net4Forest, Erasmus+, quality classes, wood defects, quality wood, forest fires, roundwood sales
Objavljeno v DiRROS: 22.03.2021; Ogledov: 846; Prenosov: 482
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