Showing papers in "Fire Safety Journal in 2017"

A review of physics and correlations of pool fire behaviour in wind and future challenges

Abstract: This paper reviews the physics and correlations for the burning behaviour of pool fires in wind, discussing also challenges for future research on this topic In the past decades, the burning behaviour of pool fires in still air, which is solely buoyancy driven, has been extensively studied These studies are primarily focused on scale, radiation, soot, pressure and gravity effects However, these phenomena and physics change significantly with much more complexity in the presence of wind, with regard to heat feedback and burning rate; flame morphological characteristics; flame turbulence, soot and radiation emission Remarkable progress has been made in understanding the behaviour of the heat feedback and burning rate, flame tilt, flame length and flame base drag of wind-blown pool fires Several semi-empirical correlations have been proposed for these quantities, based on experimental data and the physically dimensional analysis However, for wind-blown pool fires, the flame soot and radiation emission coupling with complex flow turbulence scales due to the interaction of buoyancy with wind still require more basic research All these processes are more challenging especially for wind-blown large scale pool fires, which require knowledge and understanding of the physics, especially for establishing evaluation methodologies of their hazard and adverse impact

A tunnel evacuation experiment on movement speed and exit choice in smoke

Abstract: In order to increase the knowledge on human behaviour in smoke, an evacuation experiment was performed in a road tunnel in Stockholm in July 2014. Sixty-six participants, who were instructed to individually evacuate the tunnel, took part. Participants' walking speeds were measured in a smoke-filled section, as well as in a smoke-free section, of the tunnel. The walking speeds in non-irritant smoke were measured for extinction coefficients in the range of 0.5–1.1 m-1, which corresponds to approximately 2–4 m of visibility (for light reflecting signs). In addition, way-finding and exit choice in smoke were also investigated. Particularly, different emergency exit portal designs were evaluated in the smoke-filled section of the tunnel. The novel data-set on walking speed in smoke is presented, including coupled data on obstructed (movement in smoke) and unobstructed (smoke-free movement) walking speed. Results show that there is a weak relationship between an individual's ability to walk in smoke and the unobstructed walking speed, but more research is needed in this area. In addition, the results relating to way-finding and exit choice demonstrated that the emergency exit portal design in the experiments was appropriate for the intended use. However, in order to increase the performance of the design, the portal may be complemented with information signs on the wall opposite to the exit, namely way-finding signs including distances to the closest emergency exits on both tunnel walls, and a loudspeaker installation that can inform evacuees about the location of available exits.

Wildland fire spot ignition by sparks and firebrands

Abstract: Wildland and Wildland Urban Interface (WUI) fires are an important problem in many areas of the world and may have major consequences in terms of safety, air quality, and damage to buildings, infrastructure, and the ecosystem. It is expected that with climate changes the wildland fire and WUI fire problem will only intensify. The spot fire ignition of a wildland fire by hot (solid, molten or burning) metal fragments/sparks and firebrands (flaming or glowing embers) is an important fire ignition pathway by which wildfires, WUI fires, and fires in industrial settings are started and may propagate. There are numerous cases reported of wildfires started by hot metal particles from clashing power-lines, or generated by machines, grinding and welding. Once the wildfire or structural fire has been ignited and grows, it can spread rapidly through ember spotting, where pieces of burning material (e.g. branches, bark, building materials, etc.) are lofted by the plume of the fire and then transported forward by the wind landing where they can start spot fires downwind. The spot fire problem can be separated in several individual processes: the generation of the particles (metal or firebrand) and their thermochemical state; their flight by plume lofting and wind drag and the particle thermo-chemical change during the flight; the onset of ignition (smoldering or flaming) of the fuel after the particle lands on the fuel; and finally, the sustained ignition and burning of the combustible material. Here an attempt has been made to summarize the state of the art of the wildfire spotting problem by describing the distinct individual processes involved in the problem and by discussing their know-how status. Emphasis is given to those areas that the author is more familiar with, due to his work on the subject. By characterizing these distinct individual processes, it is possible to attain the required information to develop predictive, physics-base wildfire spotting models. Such spotting models, together with topographical maps and wind models, could be added to existing flame spread models to improve the predictive capabilities of landscape-scale wildland fire spread models. These enhanced wildland fire spread models would provide land managers and government agencies with better tools to prescribe preventive measures and fuels treatments before a fire, and allocate suppression resources and issue evacuation orders during a fire.

Computer vision for wildfire research: An evolving image dataset for processing and analysis

Abstract: The last decade has witnessed the use of computer vision for wildfire detection and measurement. The first and most important step for computer vision analysis is the fire pixel detection because it determines the accuracy of the following processing. The evaluation and the comparison of the wildfire detection algorithms of the literature and the development of new ones needs open datasets with a large number of annotated images and their ground truth. We address this issue by presenting a publicly evolving wildfire annotated image database with ground truth data with examples of use. Currently, it contains 500 visible images and, in a more limited number, multimodal images and videos with frame by frame annotations. This is currently the largest dataset released in this research field.

Deep domain adaptation based video smoke detection using synthetic smoke images

Abstract: In this paper, a deep domain adaptation based method for video smoke detection is proposed to extract a powerful feature representation of smoke. Due to the smoke image samples limited in scale and diversity for deep CNN training, we systematically produced adequate synthetic smoke images with a wide variation in the smoke shape, background and lighting conditions. Considering that the appearance gap (dataset bias) between synthetic and real smoke images degrades significantly the performance of the trained model on the test set composed fully of real images, we build deep architectures based on domain adaptation to confuse the distributions of features extracted from synthetic and real smoke images. This approach expands the domain-invariant feature space for smoke image samples. With their approximate feature distribution separated from non-smoke images, the recognition rate of the trained model is improved significantly compared with the model trained directly on mixed dataset of synthetic and real images. Experimentally, several deep architectures with different design choices are applied to the smoke detector. The ultimate framework can get a satisfactory result on the test set. We believe that our method own strong robustness and may offer a new way for the video smoke detection.

Informal settlement fires in South Africa: Fire engineering overview and full-scale tests on “shacks”

Abstract: This paper discusses fires in informal settlements (otherwise known as slums, ghettos, shantytowns, etc.), which are regularly ravaged by fire in South Africa. Initially an overview of the problem is presented, highlighting the factors that contribute to the frequent, large conflagrations that occur. Details have been based on research conducted in Cape Town, South Africa, although the research is applicable to settlements worldwide. Data from recent fires where up to 4500 people were left homeless is included, highlighting aspects regarding fire spread and fire dynamics. Thereafter, preliminary results from a pilot study are presented where full-scale burn tests have been carried out on informal settlement dwellings, or “shacks”. Results from (a) a smoldering fire test, (b) 25 kg/m2 wood fire load test and (c) a ‘representative’ shack fire test are presented. For flaming fires it is shown that flashover in these small dwellings can occur in as little as one minute (depending on the fuel source), which is consistent with observations from professional firefighters in the field. Photoelectric smoke detectors, ionization, and rate-of-rise heat detectors were included during fire tests, to evaluate their performance in such confined spaces, as these are currently being either used or being considered for use in settlements. Activation times are reported for the different tests conducted.

Flame spread over horizontal and vertical wires: The role of dripping and core

Abstract: Dripping of polymer insulations in wire fire has a potential risk of igniting nearby objects and expanding the size of fire, but has not been well studied so far. In this experimental study, dripping behaviors during the flame spread over horizontal and vertical polyethylene (PE) insulated wires were investigated without external airflow. Two different wire dimensions – core/wire diameter of 3.5/8.0 and 5.5/9.0 mm – and three different PE insulations were tested. To identify effects of the core, wires with solid copper (Cu) core, hollow stainless steel (SS) core, and without core were tested, and both core and insulation temperatures were also measured during the flame spread. Experimental results showed that the high-conductance copper core acted as a heat source downstream to increase the flame-spread rate. However, in the upstream burning zone, the copper core also acted as a heat sink to cool the molten insulation and reduce its mobility. Thus, the copper core extended the residence time of molten insulation inside the flame to facilitate the burning while reducing the dripping. Moreover, for the downward flame spread, the heating by the dripping flow of hot molten insulation dominated over the heating by the core. The downward dripping flow is driven by gravity while limited by the viscous and surface tension forces. Therefore, the limited dripping flow along the cooler copper core reduced the downward flame spread. The trend of results was also found to be insensitive to the type of PE insulation. This is the first time that within a single flame, the simultaneous dual effect of the heat source and heat sink for the wire core was observed, and the influence of dripping on the flame spread over the wire was discovered.

Fire toxicity - The elephant in the room?

Abstract: Fire toxicity is the largest cause of death and injury from unwanted fires, yet it is the least well studied area of fire science and engineering. Fire toxicity increases by factors up to 50, as the fire becomes under-ventilated. This has proved difficult, but not impossible, to replicate in a controlled way on a bench-scale. Clear correlations have been observed between the stoichiometric equivalence ratio, and the yields of the major asphyxiants, carbon monoxide and hydrogen cyanide. In addition, irritant components of fire effluents, which have an instantaneous effect, can incapacitate fire victims, trapping them in a fire. However, the longer term toxicants present in fire effluents, such as the carcinogenic polycyclic aromatic hydrocarbons, and the microscopic particulates which result from their agglomeration are probably responsible for hundreds or thousands more deaths than the acute asphyxiants and irritants.

Effect of cross section on critical velocity in longitudinally ventilated tunnel fires

Abstract: Numerical and theoretical work was conducted to investigate the effect of tunnel cross section on critical velocity for smoke control in longitudinally ventilated tunnel fires. The results show that for small fires, the critical velocity decreases with both the increasing tunnel height and tunnel width. For large fires, the critical velocity significantly increases with the increasing tunnel height but is independent of tunnel width. Different calculation models are compared with a focus on effect of tunnel cross section. A new correlation is proposed to account for the effect of tunnel width based on the previous model.

Fire safety engineering in timber buildings

Abstract: The combustibility of timber is one of the main reasons that many building regulations strictly limit the use of timber as a building material Fire safety is an important contribution to feeling s

Investigation of firebrand generation from an experimental fire: Development of a reliable data collection methodology

Abstract: An experimental approach has been developed to quantify the characteristics and flux of firebrands during a management-scale wildfire in a pine-dominated ecosystem. By characterizing the local fire behavior and measuring the temporal and spatial variation in firebrand collection, the flux of firebrands has been related to the fire behavior for the first time. This linkage is seen as the first step in risk mitigation at the wildland urban interface (WUI). Data analyses allowed the evaluation of firebrand flux with respect to observed fire intensities for this ecosystem. Typical firebrand fluxes of 0.82–1.36 pcs m −2 s −1 were observed for fire intensities ranging between 7.35±3.48 MW m −1 to 12.59±5.87 MW m −1 . The experimental approach is shown to provide consistent experimental data, with small variations within the firebrand collection area. Particle size distributions show that small particles of area 0.75–5×10 −5 m 2 are the most abundant (0.6–1 pcs m −2 s −1 ), with the total flux of particles >5×10 −5 m 2 equal to 0.2–0.3 pcs m −2 s −1 . The experimental method and the data gathered show substantial promise for future investigation and quantification of firebrand generation and consequently a better description of the firebrand risk at the WUI.

A critical review of “travelling fire” scenarios for performance-based structural engineering

Abstract: Many studies of the thermal and structural behaviour for large compartments in fire carried out over the past two decades show that fires in such compartments have a great deal of non-uniformity (eg Stern-Gottfried et al [1] ), unlike the homogeneous compartment temperature assumption in the current fire safety engineering practice Furthermore, some large compartment fires may burn locally and tend to move across entire floor plates over a period of time This kind of fire scenario is beginning to be idealized as travelling fires in the context of performance-based structural and fire safety engineering This paper presents a literature review of the travelling fire research topic and its state of the art, including both the experimental and theoretical work for the past twenty years It is found that the main obstacle of developing the travelling fire knowledge is the lack of understanding of the physical mechanisms behind this kind of fire scenario, which requires more reasonable large scale travelling fire experiments to be set up and carried out The demonstration of the development of a new travelling fire framework is also presented in this paper, to show how current available experimental data hinder the analytical model development, and the urgent need that the new travelling fire experiments should be conducted

Experimental investigation on transverse ceiling flame length and temperature distribution of sidewall confined tunnel fire

Abstract: This paper presents an experimental investigation on the transverse ceiling flame length and the temperature distribution of a sidewall confined tunnel fire. The experiments were conducted in a 1/6th scale model tunnel with the fire source placed against the sidewall, 0 m, 0.17 m and 0.35 m above the floor, respectively. Experiments of fire against a wall without a ceiling, 0.35 m above the floor in a large space, were also conducted as a control group. Results shows that for small heat release rate (HRR), the flame is lower than the ceiling and extends along the sidewall. With the increase of HRR and elevation of burner height, the flame gradually impinges on the ceiling and spreads out radially along it. The flame impingement condition and the flame shapes of the wall fire with and without ceiling are presented. From the viewpoint of the physical meaning of flame impinging on the ceiling, the horizontal flame length should be a function of the unburned part of the fuel at the impinging point. Based on the proportional relation between the flame volume and HRR, the effective HRR (Qef) at the ceiling is determined and the effective dimensionless HRR, Q*ef is defined to correlate the horizontal ceiling flame length. Additionally, predictive correlations of transverse ceiling temperature distribution are proposed for the continuous flame region, the intermittent flame region and the buoyant plume region under the ceiling, respectively.

Effects of exposed cross laminated timber on compartment fire dynamics

Abstract: A series of compartment fire experiments has been undertaken to evaluate the impact of combustible cross laminated timber linings on the compartment fire behaviour. Compartment heat release rates and temperatures are reported for three configuration of exposed timber surfaces. Auto-extinction of the compartment was observed in one case but this was not observed when the experiment was repeated under identical condition. This highlights the strong interaction between the exposed combustible material and the resulting fire dynamics. For large areas of exposed timber linings heat transfer within the compartment dominates and prevents auto-extinction. A framework is presented based on the relative durations of the thermal penetration time of a timber layer and compartment fire duration to account for the observed differences in fire dynamics. This analysis shows that fall-off of the charred timber layers is a key contributor to whether auto-extinction can be achieved.

Pyrolysis and spontaneous ignition of wood under transient irradiation: Experiments and a-priori predictions

Abstract: Wood is a material widely used in the built environment, but its flammability and response to fire are a disadvantage. Therefore, it is essential to have substantial knowledge of the behavior of wood undergoing external heating such as in a fire. The majority of studies in the literature use constant irradiation. Although this assumption simplifies both modelling and experimental endeavors, it is important to assess the behavior of materials under more comprehensive heating scenarios which might challenge the validity of solid-phase ignition criteria developed previously. These criteria are evaluated here for the spontaneous ignition under transient irradiation by combining experimental measurements and a-priori predictions from a model of heat transfer and pyrolysis. We have applied a two-step transient irradiation in the cone calorimeter in the form of a growth curve followed by constant irradiation. We use white spruce samples of size 100×100 mm and thickness of 38 mm . We measure the temperature at different depths and the mass loss. A one dimensional model written in the open source code Gpyro is used to predict the pyrolysis behavior. The model has a chemical scheme in which the components of wood (hemicellulose, cellulose, lignin) become active, then decompose in two competing reactions: one reaction to char and gas, and one reaction to tar. The kinetic parameters, as well as the thermal properties of the wood and char are taken from the literature, while ρ and moisture content are measured experimentally. A priori predictions of the temperature, made prior to the experiments, show excellent agreement with the measurements, being within the experimental uncertainty range. The mass loss rate (MLR) predictions are qualitatively similar to the measurements, but there is a large uncertainty in the measurements. For a-posteriori simulations, certain parameters are changed after having access to the measurements to improve the simulations. Also, we perform an evaluation of the solid phase ignition criteria used in the literature, and find that neither criteria is a consistent indicator of ignition. These results help understand the spontaneous ignition of wood subjected to transient irradiation and identify strengths and gaps in the topic.

Flame-retardant wood polymer composites (WPCs) as potential fire safe bio-based materials for building products: Preparation, flammability and mechanical properties

Abstract: Improving the efficiency of traditional flame retardant additives is a challenging task in the field of wood polymer composites (WPCs). In this work, novel flame retardant system for WPCs was developed based on the combination of ammonium polyphosphate (APP) with phytic acid modified layered double hydroxide (Ph-LDH). Thermogravimetric analysis illustrated that the incorporation of Ph-LDH resulted in earlier thermal degradation of the WPCs with more thermally stable products during degradation, giving improved char formation. Limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimetry tests were used to study the flammability of WPCs and the results showed that the addition of Ph-LDH had a synergistic effect on their fire performance. The char residues of the WPCs after the cone calorimetry tests were characterised by scanning electron microscopy (SEM). Mechanical properties of the flame retardant WPCs were analysed using impact and tensile tests. Partial substitution of APP with polypropylene (PP) resulted in a deterioration in the tensile and impact properties, while co-incorporation of nano-fillers led to an enhancement of the mechanical performances of the flame retardant WPCs. This WPC with good flame retardant and mechanical properties could potentially be used in the fields of building or furniture which require high flame retardancy.

Bond strength of steel bars embedded in high-performance fiber-reinforced cementitious composite before and after exposure to elevated temperatures

Abstract: Interfacial bond strengths of steel reinforcing bars embedded in a high-performance fiber-reinforced cementitious composite (HPFRCC) are investigated in this paper. Out of 303 pullout specimens, 48 HPFRCC and 3 normal concrete specimens were tested without any heat treatment, and 240 HPFRCC and 12 normal concrete specimens were heated at 200, 400, 600, or 800 °C in a furnace for 2 h prior to testing. The effects of bar shape, diameter, and length embedded in HPFRCC on the bond strength of HPFRCC specimens were investigated. The bond strength decreased with the heating temperature and with the size and embedded length of steel bars. It was reduced further when the heated specimens were cooled in water instead of air. It was disaggregated into chemical adhesion and mechanical interlock from a comparative study of plain and deformed bars. The mechanical properties and microstructures of HPFRCC specimens before and after heat treatment were compared to understand the mechanisms of interfacial bonding degradation due to heat treatment.

Evaluating the effectiveness of an improved active dynamic signage system using full scale evacuation trials

Abstract: The need for exit signs that attract attention when they need to be conspicuous, to redirect people to not just an exit route, but a viable and if possible an optimal exit route in an evolving emergency has driven the development of a new generation of advanced signage, the Intelligent Active Dynamic Signage System (IADSS). The IADSS, attempts to meet these needs through the development of a novel Active Dynamic Signage System (ADSS) which can be controlled by an intelligent decision support system. This paper presents results that refine the effectiveness of the ADSS. When an exit route is considered non-viable, the adapted ADSS provides not only negative information i.e. that an exit is no longer available, but also positive information, i.e. indicating a viable alternative exit. In addition, in situations where a voice alarm system is used in conjunction with the ADSS, it is also important to ensure that the messaging does not contradict the intent of the ADSS. The improved ADSS was tested in full-scale evacuation trials in a rail station. Results suggest that the improved ADSS with voice alarm messaging that does not contradict the signage system successfully redirected 66% of the participants to the intended exit.

Pyrolysis kinetics and multi-objective inverse modelling of cellulose at the microscale

Abstract: The chemistry of pyrolysis, together with heat transfer, drives ignition and flame spread of biomass materials under many fire conditions, but it is poorly understood Cellulose is the main component of biomass and is often taken as a surrogate for biomass Its chemistry of pyrolysis is simpler and dominates the pyrolysis of biomass Many reaction schemes with corresponding kinetic parameters can be found in the literature for the pyrolysis of cellulose, but their appropriateness for fire is unknown This study investigated inverse modelling and blind predictions of six reaction schemes of different complexities for isothermal and non-isothermal thermogravimetric experiments We used multi-objective optimisation to simultaneously and separately inverse model the kinetic parameters of each reaction scheme to several experiments Afterwards we tested these parameters with blind predictions For the first time, we reveal a set of equally viable solutions for the modelling of pyrolysis chemistry of different experiments This set of solutions is called a Pareto front, and represents a trade-off between predictions of different experiments It stems from the uncertainty in the experiments and in the modelling Parameters derived from non-isothermal experiments compared well with the literature, and performed well in blind predictions of both isothermal and non-isothermal experiments Complexity beyond the Broido-Shafizadeh scheme with seven parameters proved to be unnecessary to predict the mass loss of cellulose; hence, simple reaction schemes are most appropriate for macroscale fire models Modellers should, therefore, use simple reaction schemes to model pyrolysis in macroscale fire models

Modeling for predicting the temperature distribution of smoke during a fire in an underground road tunnel with vertical shafts

Abstract: In this study, fire experiments using a 1:20 model-scale tunnel were conducted to investigate the performance of natural ventilation in an underground road tunnel with six vertical shafts. The experimental parameters were the heat release rate of a fire source and the height of the shafts, and nine experiments were conducted in total. Furthermore, simple models were developed for predicting the temperature distribution of the smoke flowing under the tunnel ceiling. The following results were obtained: (1) In the experiments, the form of the smoke exhausted from the shaft became plug-holing when the shaft height was 1.0Ht, and became boundary layer separation when the height was 0.24Ht. (2) The average efficiency of heat exhaust was 0.16 when the form was plug-holing, and was 0.12 when the form was boundary layer separation. (3) When the form was plug-holing, the ratio of entrainment of fresh air became almost constant regardless of Ri. On the other hand, when the form was boundary layer separation, the ratio of entrainment of fresh air was smaller than that under the condition of plug-holing. (4) The temperature distribution under the tunnel ceiling predicted by the models agreed with that measured by the fire experiments in all cases.

The effect of flow and geometry on concurrent flame spread

Abstract: Flame spread is an important parameter used in the evaluation of hazards for fire safety applications The problem of understanding and modeling flame spread has been approached before, however new developments continue to challenge our current view of the subject, necessitating future research efforts in the field In this review, the problem of flame spread will be revisited, with a particular emphasis on the effect of flow and geometry on concurrent flame spread over solid fuels The majority of this research is based on that of the senior author, who has worked on wind-driven flame spread, inclined fire spread, flame spread through discrete fuels and the particular problem of wildland fires, where all of the above scenarios play an important role Recent developments in these areas have improved our understanding of flame-spread processes and will be reviewed, and areas for future research will be highlighted

An experimental study of full-scale open floor plan enclosure fires

Abstract: A full-scale experimental series is undertaken to generate a comprehensive data set to study and characterise fires in large open-plan spaces, typical of contemporary infrastructure and Tall Buildings in particular. Developments in the understanding of enclosure fire dynamics for large spaces is intended to complement the knowledge of relatively smaller, low ventilation spaces developed from the extensive body of research that underpins the original compartment fire framework. A total of twelve experiments are conducted, ten using box gas burners and two using a bed of wood cribs. Both the fire development and ventilation characteristics are varied systematically to enable the careful examination of the effect of each on the fire dynamics within the compartment. For this set of tests, sensor instrumentation is, as far as practicable, provided at a resolution to enable benchmarking of field models. These tests form part of the Real Fires for the Safe Design of Tall Buildings Project. The current paper, the first in a series of publications, provides a thorough description of the full-scale experimental compartment, the various sensing techniques deployed within it, and the range of combined fire and ventilation conditions for each of the twelve tests performed. Characteristic results from the first experiment that forms part of the ‘Edinburgh Tall Building Fire Tests’ (ETFT) test series are presented.

Spontaneous combustion coal parameters for the Crossing-Point Temperature (CPT) method in a Temperature–Programmed System (TPS)

Abstract: Coal fires originate from coal spontaneous combustion caused by oxidation starting even at low temperatures. In order to evaluate the heating and oxidation of coal placed inside a container, a Temperature-Programmed System (TPS) is used under various flow and oxidation conditions for temperatures ranging from 40 to 250 °C. As the coal samples are heated in the container within the TPS, the concentration histories of the gaseous products are measured as well as the temperature history at the center of the container. The Crossing-point Temperature (CPT) is the temperature (temperature and corresponding time) at which the increasing coal temperature is equal to the increasing oven temperature within the TPS. We have developed energy and oxygen mass conservation equations for the coal pile in a container inside the TPS oven assuming uniform conditions for temperature and oxygen concentrations, both assumptions partially justified because the heating rate in the oven is very low (1 °C/min). By subtracting the convective heat from the thermal inertia of the coal pile in the energy equation, we have obtained from the experimental data the heat owing to oxygen reaction or moisture evaporation. From the oxygen conservation and measurements, we have determined apparent activation energy and pre-exponential factor for oxidation assuming that oxidation is proportional to oxygen concentration. This information is useful for the mathematical modeling of oxidation and heating in the present experiments. Subsequently, the energy and mass conservation equations were solved after being transformed to non-dimensional form, which shows that four dimensionless parameters control the heating of coal in the present experiments. Only three of these parameters are examined in detail, namely a dimensionless flow time, a heat release parameter B , and a Damkohler number Da whereas a moisture parameter is discussed qualitatively. Based on the present analysis and data, four stages are identified: (I) initial heating with essentially no reaction or evaporation, (II) evaporation period with essentially no reaction, (III) an unsteady accelerated oxidation period during which crossover may occur and (IV) a heating late period where all the oxygen reacts inside the container.

Experimental investigation on thermal and mechanical behaviour of composite floors exposed to standard fire

Abstract: This paper presents experimental investigations on the thermal and mechanical behavior of composite floors subjected to ISO standard fire. Four 5.2 m×3.7 m composite slabs are tested with different combinations of the presence of one unprotected secondary beam, direction of ribs, and location of the reinforcement. The experimental results show that the highest temperature in the reinforcements occurs during the cooling phase (30–50 °C increment after 10-min cooling). The temperature at the unexposed side of the slabs is below 100 °C up to 100-min heating, compared to the predicted fire resistance close to 90 mins from EC4. For the slabs without secondary beams, the cracks first occur around the boundaries of the slab, while for the slabs supported by one unprotected secondary beam, concrete cracks first occur on the top of the slab above the beam due to the negative bending moment, and later on develop around boundaries. Debonding is observed between the steel deck and concrete slab. The secondary beam significantly impacts the deformation shape of tested slabs. Although a large deflection, 1/20 of the span length, is reached in the tests, the composite slabs can still provide sufficient load-bearing capacity due to membrane action. The occurrence of tensile membrane action is confirmed by the measured tensile stress in the reinforcement and compressive stress in the concrete. A comparison between measured and predicted fire resistance of the slabs indicates that EC4 calculations might be used for the composite slabs beyond the specified geometry limit, and the prediction is conservative.

Fire impact assessment in FLNG processing facilities using Computational Fluid Dynamics (CFD)

Abstract: Increasing demand for natural gas has pushed the exploration of natural gas to remote offshore locations using a Floating LNG (FLNG) facility. In this facility, fire hazards are comparatively high and even a single fire accident may be catastrophic due to the congested and complex layout of the facility. This study proposes a novel methodology for modelling the impact of a fire event in an FLNG facility. Hazard identification and accident credibility assessment have been used to discover the three most credible fire accident scenarios. These scenarios have been simulated using Computational Fluid Dynamics (CFD) code, Fire Dynamics Simulator (FDS). The results have then been compared to identify the most severe impact of the fire on personnel and assets using thermal radiation and risk levels. It has been found that the fire event in all three scenarios has a high potential to cause damage to adjacent assets. From this comparison, it is evident that the scenario in the Mixed Refrigerant Module in the liquefaction process has the highest risk of fire to both on-board personnel and assets. The proposed methodology may be adopted further for safety measure design to mitigate or avoid the impacts of a fire event in any complex processing facility.

Hydrocarbon flame inhibition by C6F12O (Novec 1230): Unstretched burning velocity measurements and predictions

Abstract: This study experimentally and numerically determined the unstretched laminar burning velocity of premixed CH4-air and C3H8-air flames with added C6F12O (Novec 1230). High-speed shadowgraphy of spherically expanding flames provided the burning velocity as a function of stretch, which was extrapolated to zero-stretch conditions using non-linear methods. Unstretched burning velocities predicted using a recently assembled kinetic mechanism were generally in good agreement with the measurements, but tended to have poorer agreement for highly-inhibited very lean flames. To benchmark the performance of C6F12O, measured burning velocities were compared to previously measured burning velocities of premixed flames inhibited by CF3Br (Halon 1301). The two agents provided similar reductions in the burning velocity of rich flames, whereas CF3Br provided greater reductions when added to stoichiometric and lean flames. Lastly, experiments and simulations showed the influence of water vapor on the burning velocity of lean C3H8-air flames with added C6F12O. The presence of water vapor in the oxidizer increased the burning velocity by up to 23% when the fluorine to hydrogen ratio of the reactant mixture was greater than unity.

Spilled liquid fires in tunnels

Abstract: The study focuses on release of liquids inside tunnels from tankers containing dangerous good. Experiments and analysis from large scale tests are presented. The tests include different leakage rates, leakage type, liquids, spillage sizes on sloping surfaces and heat release rates. Models for estimation of leakage rates, spillage sizes and heat release rates for different scenarios are presented. The results are important to use in the design of active fire protections systems in tunnels including ventilation, fixed fire-fighting and drainage systems.

Structural response of a steel-frame building to horizontal and vertical travelling fires in multiple floors

Abstract: During previous fire events such as the World Trade Centre Towers (WTC) 1, 2 & 7 in New York (2001), the Windsor Tower in Madrid (2005), and the Plasco building in Iran (2017), flames were observed to travel horizontally across the floor plate and vertically to different floors. Such fires are not considered as part of the traditional prescriptive structural design for fire. Recently, the Travelling Fires Methodology (TFM) has been developed to account for such horizontally travelling nature of fires. A dozen of studies have investigated the structural response of steel, concrete, and composite structures to a single-floor travelling fire. 5 out of 6 of the vertically travelling fire studies have been limited to the structures with a long span composite truss system as in the WTC Towers. The aim of this work is to investigate the response of a substantially different structural system, i.e. a generic multi-storey steel frame, subjected to travelling fires in multiple floors, and varying the number of fire floors, including horizontal and vertical fire spread. A two-dimensional 10-storey 5-bay steel frame is modelled in the finite element software LS-DYNA. The number of multiple fire floors is varied between 1 and 10, and for each of these scenarios, 5 different fire types are investigated. They include four travelling fire scenarios and the standard fire. In total, 51 fire simulations are considered. The development of deflections, axial forces, bending moments and frame utilization are analysed. Results show that the largest stresses develop in the fire floors adjacent to cool floors, and their behaviour is independent of the number of fire floors. Results indicate that both the fire type and the number of fire floors have a significant effect on the failure time (i.e. exceeded element load carrying capacity) and the type of collapse mechanism. In the cases with a low number of fire floors (1–3) failure is dominated by the loss of material strength, while in the cases with larger number of fire floors (5–10) failure is dominated by thermal expansion. Collapse is mainly initiated by the pull-in of external columns (1–3-floor fires; 1–9-floor fires for 2.5% TFM) or swaying of the frame to the side of fire origin (5–10-floor fires). This study has assessed a different structural form compared to previous literature under an extensive range of multiple floor travelling fire scenarios. We find that although vertically travelling fires result in larger beam axial forces and initial deflections, simultaneous travelling fires result in shorter failure times and represent a more onerous scenario for the steel frame investigated.

Facade flame height ejected from an opening of fire compartment under external wind

Abstract: This paper presents an experimental study and analysis on the facade flame height ejected from an opening of fire compartment under external wind. Experiments are carried out in a reduced-scale model consisting of a cubic fire compartment with a vertical facade wall. An opening is designed at the center of one sidewall of the fire compartment at the facade side and subjected to external wind (normal to the opening) provided by a wind tunnel. The facade flame heights are measured by a CCD camera for five different openings at various fuel supply heat release rates and wind speeds. It is found that the facade flame height decreases with increasing external wind speed. A scaling analysis is performed to interpret this behavior based on the change of air entrainment into the flame from both the facing-facade and parallel-facade directions caused by the external wind flow. A global model incorporating the external wind speed, the two characteristic length scales of the opening as well as the dimensionless excess heat release rate is developed for describing the facade flame height of various conditions. The proposed model correlates the experimental data well.

The potential of integrating fire safety in modern building design

Abstract: Whether explicitly acknowledged or not, modern building design is strongly influenced by fire safety considerations. The building design community, broadly construed, appears to remain surprisingly unaware of the extent to which prescriptive fire safety considerations impact building designs. However, several decades of advances in fire safety science have gradually revealed the potential value of integrating fire safety as one of the many variables that should be optimized during the building design process. This paper presents outcomes from a series of mediated roundtable discussions that occurred during an international seminar aimed at reflecting on the current status of fire safety and fire protection concepts within overall building design processes. An attempt is made to emphasize discrepancies between the perceptions of fire safety considerations, requirements, and drivers exemplified by the various stakeholder participants. A distinction is made between the status of those individuals presently charged with the fire safety design of a building, and the future potential for further integration of fire safety considerations within the building design process. Fundamental changes in support of holistic provision of fire safety in the modern built environment are proposed.