Search

Fire can cause devastating damage to ancient buildings; therefore, a theoretical basis regarding the stages of fire development and fire extinguishing studies in historical buildings is provided by studying the release patterns of combustion gas products from ancient building timbers. In this paper, TG-MS-FTIR experiments were employed to investigate the gas products and release patterns of ancient building wood during pyrolysis. Meanwhile, PY-GC/MS experiments were carried out in a helium atmosphere at temperatures to study the thermal cracking products of ancient building wood. From the experiments, it can be concluded that the values of the activation energy of ancient building wood range from 78.93395 to 209.8952 KJ/mol, with a maximum value at a conversion rate of 0.3 and a minimum value at a conversion rate of 0.9. The gasses produced during the pyrolysis of ancient construction wood were mainly CO, H 2 O, CO 2, and CH 4 , and the mass spectrometry analysis showed that H 2 O had a double peak shape, CH 4 had only one peak, and CO 2 had two peaks. The overall trend of CO precipitation is that the amount of CO precipitation increases first and then decreases, and the amount of CO precipitation increases slowly at temperatures above 520 °C. The DTG maxima of ancient building timber differ considerably from those of fresh wood. This is due to the release of terpenes, which affect the intensity of their combustion. At the same time, the lignin content of ancient building timber is reduced, and the pyrolysis of lignin inhibits the pyrolysis of cellulose to a certain extent. There is a greater difference between ancient building timber and fresh wood at approximately 300 °C due to the decrease in lignin content. [ABSTRACT FROM AUTHOR]

There is a class of heritage buildings, such as museums, palaces and castles, which are closed buildings with multiple layers and exits. There are a lot of precious heritage and cultural relics in heritage buildings, and a large number of tourists need to be received every day. When suffering from emergencies such as fires, heritage buildings will be confronted with serious consequences if individuals cannot evacuate in time. In this paper, the path intelligent optimization for dense crowd emergency evacuation is proposed in heritage buildings. Firstly, based on Artificial Fish Swarm Algorithm (AFSA), agglomeration model is used when there is no guidance of guide personnel. Secondly, single-layer evacuation model is used to classify individuals into different categories based on improved K-Nearest Neighbor (KNN) algorithm. The model can help individuals choose the nearest stair and save escape time. Thirdly, based on Dijkstra shortest path algorithm, multi-layer evacuation model is used to find the shortest distance and the optimal path for individuals to reach the exit. These models are applied to the Louvre in order to verify the rationality by calculating the approximate evacuation time. In case of emergency, the algorithm proposed in this paper can be modified according to the actual heritage buildings. [ABSTRACT FROM AUTHOR]

In the past decades, increasing attention has been directed to understanding the structural response to various scenario fires, which is stimulated by the trend of considering localised burning in large open plan compartments. Beam-column elements as widely used in modelling steel frames have been extended to account for the thermal impact in OpenSees, the development of which is undertaken to formulate the displacement and force-based beam elements. After including the non-uniform thermal expansion along the element length caused by localised heating, the force-based beam-column element has shown greater efficiency compared to the displacement-based element. A detailed discussion regarding the computational performance of both beam-column elements has been presented in this paper, which concludes that force-based beam-column elements can better represent the localised plasticity of fibres caused by non-uniform heating. A generic simply supported steel beam can be modelled even with two force-based elements to reproduce accurate mid-span deflection under localised heating. A steel beam subjected to a localised fire is presented as a case study in this paper, experiencing run-away collapse after 15 min of exposure when the load ratio reaches 50%. Using a 12 element force-based beam-column model and shows equivalent accuracy against 48 element displacement-based beam-column model. [ABSTRACT FROM AUTHOR]

• A comprehensive review of LL fault diagnosis methods in PV systems. • An ensemble learning model based on probabilistic strategy is developed. • The main features of the fault are extracted from I-V curves using a Simulink based model of PV arrays. • A feature selection algorithm is used for each learning algorithm to reduce the dataset and increase the classification accuracy. • The proposed model is very reliable and able to detect and classify all the LL faults accurately. The fault diagnosis of photovoltaic (PV) arrays aims to increase the reliability and service life of PV systems. Line-Line (LL) faults may remain undetected under low mismatch level and high impedance due to low currents of faults, resulting in power losses and fire potential disaster. This paper proposes a novel and intelligent fault diagnosis method based on an ensemble learning model and Current-Voltage (I-V) characteristics to detect and classify LL faults at the DC side of PV systems. For this purpose, first, the key features are extracted via analyzing I-V characteristics under various LL fault events and normal operation. Second, a feature selection algorithm has been applied to select the best features for each learning algorithm in order to reduce the amount of data required for the learning process. Third, an ensemble learning model is developed that combines several learning algorithms based on the probabilistic strategy to achieve superior diagnostic performance. Here, we find an excellent agreement between simulation and experimental results that the proposed method can obtain higher accuracy in detecting and classifying the LL faults, even under low mismatch levels and high fault impedances. In addition, the comparison results demonstrate that the performance of the proposed method is better than individual machine learning algorithms, so that the proposed method precisely detects and classifies LL faults on PV systems under the different conditions with an average accuracy of 99% and 99.5%, respectively. [ABSTRACT FROM AUTHOR]

• Modelling and characterisation of fire-spotting generated fires. • Study the effects of the atmospheric stability conditions on the behaviour of fire-spotting generated fires. • During stable conditions, there are many active fires because turbulent heat transport does not merge them rapidly. • During unstable conditions, the formation of unburned islands surrounded by the fire are observed. • Different atmospheric stability conditions cause different risks requiring different management. This is the first part of two papers concerning fire-spotting generated fires. In this part we deal with the impact of macroscale factors, such as the atmospheric stability, and in the second part we deal with mesoscale factors, such as the flame geometry. For this study we adopt an approach where the motion of the front is split into a drifting part and a fluctuating part. The drifting part, that can be provided by choosing an existing operational model, is here based on the level-set method in analogy with WRF-SFIRE model. The fluctuating part, that is the result of a comprehensive statistical description of the physics of the system and includes the random effects, is here physically parametrized to include turbulent hot-air transport and firebrand landing distance. In order to highlight the net effects of the random contributions due to turbulence and firebrand flying, a simplified model without fire-atmosphere coupling is considered. Numerical simulations show that the atmospheric stability is an important factor for wildfire propagation. In particular, unstable conditions boost the number of fire-spotting generated fires at small elapsed times as well as the strength of turbulence leading to rapid merging and the formation of unburned islands surrounded by the fire. Stability conditions have then an effect on the risk and the management associated to fire-spotting generated fires. In fact, with stable conditions (corresponding for example to the night-time) the turbulence is not strong enough to merge the fires and, at large elapsed times, this results into a higher number of independent fires but lower burned area with respect to unstable conditions (corresponding for example to the day-time) when the push of turbulence leads to faster merging resulting into a lower number of independent fires but higher burned area. Finally, with stable conditions less fire fronts need to be managed at short time, but more fire fronts need to be managed than with unstable conditions that however show a higher risk because of the merging of independent fires. [ABSTRACT FROM AUTHOR]

The combustion behavior of two oil tank fires will be influenced by the interaction of their respective flames. This paper presents the experiments to investigate the evolution of the visible flame height of two oil tank fires under different diameters, lip heights and distances. The results show that when the tank spacing is small, the vortex structure plays an important role in the flame behavior showing an enhancement of the flame height. The flame height increases with the increase in lip height and reaches a local maximum value. The flame merging characteristic is influenced by the burner size and shape. A dimensionless model of the visible flame height of two oil tanks fire has been proposed, taking the tank diameter, lip height, and tank spacing into consideration. The correlation is validated using the experimental data. [ABSTRACT FROM AUTHOR]

A series of experiments were carried out to investigate the effect of ullage height, i.e. the distance between fuel surface and the pool upper rim, on flame characteristics of heptane and ethanol pool fires. The pool diameters included 10 cm, 15 cm, and 20 cm. For each pool, ullage height was increased from zero to the value that the flame self-extinguished. During each test, the ullage height was kept constant by a fuel level maintaining device. Results show that ullage height has a significant effect on flame characteristics. When the ullage height equals zero, there is a stable conical structure near the pool upper rim, above which the unstable plume develops. Under lower ullage height conditions, plume puffing happens. The unstable plume begins to initiate around the pool upper rim, then rolling and expanding upward. At the same time, its beneath flame is stretched thinner and thinner and eventually breaks from the bulk. When the ullage height further increases, plume puffing becomes less evident. While for the mass loss rate, it generally decreases with the increase of h / D. It was proved in literature that the previous flame height model is inapplicable to pool fires with large ullage height. In this paper, to consider the effect of ullage height on plume flow structures, an equivalent hydraulic diameter, D eq. , is proposed to establish one new flame height correlation. By comparing previous model predictions with the current experimental data, it is found that conventional flame oscillation models are unsuitable to pool fires with large ullage height. Based on D eq. , two new dimensional and dimensionless flame oscillation models were proposed according to the current experimental data. The correlated flame height model and proposed flame oscillation models were validated and agreed well with reference data. [ABSTRACT FROM AUTHOR]

A car accident involving the oil tank may result in continuously spreading spill fires in tunnels, which poses great threats to the entrapped cars. However, there is still no relevant work concerning this issue. This paper experimentally investigates the spill fires in a tunnel by means of a model-scale tunnel and a steel trench where the liquid fuel flows and burns. The findings show that in a quiescent environment, the burning area of the spill fires in the tunnel is notably smaller than that in open space, while the presence of wind influence the burning area significantly, largely depending on the wind speed. For all the tests, there is no obvious steady burning stage, instead a rebound in burning area is observed after a similar shrinking burning area as that in open space. Generally, the burning area initially increases and then decreases with the increasing wind speed. These findings provide a better understanding of spill fire behaviors in tunnels and can further offer guidance on the firefighting of such fires. [ABSTRACT FROM AUTHOR]

The interaction between jet flame and vortex flow is a fundamental combustion phenomenon which could occur in actual fire accidents. This paper presents a systematical investigation on such jet fire in a rotating flow field (JFRFF). A new facility was designed for the experimental study, which consists of a jet fire apparatus and a whirl generator. The test repeatability was justified for the proposed facility. The dynamical differences of JFRFF, free jet fire and fire whirl are clarified. A set of correlations are proposed for the flow circulation, flame height, lift-off height and frequency of flame wander of JFRFF. The flow circulation is found to well couple the inlet velocity and the flow guide angle as Γ = 0.80 π D d u a sin θ. The results have also shown that the JFRFF has a larger flame height than the free jet fire in still air, while the lift-off height is shorter than the free jet fire. Theoretical analysis identifies two competitive effects of flow circulation on the flame height of JFRFF. The enhancement of air entrainment in the ground layer reduces the flame height by decreasing the jet momentum, whereas the reduction of fuel-air mixing rate in the upper flame increases the flame height. The flow circulation reduces the vertical velocity of gas mixtures in the ground boundary layer, resulting in a less lift-off height. However, similarly as for fire whirls, the flame of JFRFF wanders as whole with the centerline being not completely perpendicular to the horizontal plane, and the appearance probability of flame fits Gauss distribution. It is also found that the frequency of flame wander can be positively correlated to the tangential component of inlet velocity. [ABSTRACT FROM AUTHOR]

This paper describes a programme of blind modelling and benchmarking experiments that was part of a larger collaborative research project. The modelling and subsequent experiments were performed for a compartment representing a typical lounge in a residential occupancy with a number of different combustible items located in pre-defined positions, and a specific ignition source. The modellers were provided with information such as the compartment dimensions and number/size of ventilation openings, the location and nature of the combustible items, and the details of the ignition source. The objective for the blind modelling was to predict both the ignition times for each of the secondary items, as well as the heat release rate for the compartment. As input for the blind modelling, each modeller had to select a range of different input data that included a heat release rate curve and ignition properties for each combustible item. A series of three identical experiments were then carried out and the blind modelling predictions were compared to the experimental results. The specific focus of this paper is to describe what choices the different modellers made when selecting the different input data for the blind modelling exercise. The impact that this decision-making had on the predictions, and hence comparison with the subsequent experimental data, is discussed. The input data varied considerably between the different modellers, and this had a significant impact on the modelling predictions and the comparison with the experimental results. The user decision-making in this blind modelling and experimental benchmarking programme provides an illustration of one of the many aspects of the significant subjectivity that is likely to occur in everyday performance-based fire safety engineering (PBFSE). A comprehensive performance-based design will involve a number of performance objectives. The modelling and experimental programme presented in this paper deals with only one aspect of a life safety performance objective. Notwithstanding this limitation, any subjectivity of the type illustrated in this paper has the potential to create uncertainty as to the actual level of safety that will be achieved, a lack of confidence in the eyes of an official who may be reviewing/approving a design, and hence provide a barrier to the effective implementation of PBFSE. [ABSTRACT FROM AUTHOR]

• Characteristics of a tunnel fire during construction are studied in a model-scale tunnel. • Equivalence ratio for self-extinguishment is within 0.28–1.38 for propane burner and 1.11–3.6 for fibre board with heptane. • Fire in the inclined access tunnel does not self-extinguish even the ventilation rate is 0 m3/s. • A recirculation of vitiated fire products is formed for a fire in the closed end of the main tunnel (excavation face). • Smoke spreads over the entire cross section and the smoke spread velocity is proportional to the ventilation rate. The paper presents a study on the characteristics of tunnel fires during construction. A model-scale tunnel was built and fire tests were conducted. The tunnel consists of an inclined access tunnel and a horizontal main tunnel. The main tunnel has two dead ends (excavation faces) and the only opening is from one side of the access tunnel. Propane gas burner and the fibre board soaked with the heptane were used as fuels. The flame characteristics, O 2 and CO volume fraction and gas temperature were measured and recorded. Two typical characteristics of self-extinguishment and smoke spread were found in the tunnel fires during construction. Results indicate that when a fire occurs in the horizontal main tunnel, the critical equivalence ratio for the occurrence of self-extinguishment is within 0.28–1.38 for the propane gas burner and 1.11–3.6 for the fibre board soaked with heptane. The difference is related to the burning behavior of the different fuels used. The fire location in the horizontal tunnel also has a significant influence on the fire development. A well-ventilated fire at the center of the horizontal tunnel becomes under-ventilated due to vitiation when it is located at the closed end of the horizontal tunnel. Besides, when a fire occurs at the closed end of the horizontal main tunnel, the stratification of smoke is destroyed after hitting the closed end, and then the smoke seems to spread over the entire cross section of the tunnel. The smoke spread velocity is found to be proportional to the ventilation rate. However, when a fire occurs at the closed end of the inclined access tunnel (lower end), the fire does not self-extinguish, even when the ventilation rate is 0 m3/s. The corresponding smoke spread velocity is higher than that in the horizontal main tunnel. The outcomes of this study provide new experimental information that contributes to improve the understanding of characteristics of tunnel fires during construction and can help firefighters to make better decisions during the rescue processes. [ABSTRACT FROM AUTHOR]

• Fire exposure influences the behaviour of RC connections during collapse. • Variation of reinforcement detailing at beam end influences collapse response of RC connections. • The simplified model accounts for the combined loading states due to axial restraint and fire. • Practical considerations are highlighted to improve the rotational capacity. This paper examines the behaviour of RC beam-column joints with different reinforcement detailing arrangements under pushdown loading before and after fires. The thermal responses of the RC joint specimens are firstly described, including the development of the temperature fields and the horizontal reactions as well as the deflections during the heating and cooling phases. Subsequently, displacement-controlled push-down tests are performed, and the vertical load, horizontal reactions as well as detailed deformations are monitored. The bending moment-rotation relationships are derived from the test results, together with an account of the observed failure modes. The mechanical behaviour is also discussed in detail, including the rotational capacity, with emphasis on the effect of different reinforcement detailing arrangements as well as the post-fire condition. Particular attention is given to comparing the experimental axial-moment strength interaction curves and theoretical predictions under ambient conditions so as to examine the underlying mechanisms. In order to support practical application, a simplified analytical method is proposed for simulating the push-down response, based on the combined loading states and idealised constitutive relations, taking into consideration the restraint effect due to horizontal restraint or fire conditions. The suggested analytical procedure is shown to be a reliable and effective approach for representing the behaviour. Based on the findings of this investigation, practical considerations for enhancing the rotational capacity of RC joints are highlighted. [ABSTRACT FROM AUTHOR]

Highlights • The characteristics and hazards of multiple pool fires in tunnels were studied. • A fundamental guide for understanding the multiple fires in tunnels was provided. • Effect of fire number and fire spacing on fuel burning rate was well addressed. • An empirical model was proposed to predict the average burning rate. Abstract Tunnel fires are usually accompanied with major casualties and properties losses, and multiple fires in a tunnel may cause intense burning behavior like fire merging, which could be more destructive and hazardous. Therefore, the characteristics and hazards of multiple pool fires in a tunnel were investigated under natural ventilation in this study through a series of experiments. Experimental results showed that the characteristics of one-dimensional fire arrays were different from those of square fire arrays in open space. Due to the extra heat feedbacks (e.g. from adjacent fire sources, tunnel wall and hot smoke), the burning rate was found being enhanced. When there is more than one fire source, it was observed that the flames deflect towards the center of one-dimensional fire arrays, leading to flame merging when fire spacing decrease to some extent, which would result in the increased hazards of the heptane fires. An empirical model was developed to predict the global dimensionless average burning rates based on modified fire area ratio, which characterizes the fuel load and incorporated fire spacing, fire number and the fuel pan size. The research results in this paper provide a theoretical guide on understanding the behaviors of multiple fire resources in tunnels. [ABSTRACT FROM AUTHOR]

Abstract This paper investigates building eave effect of fire-induced ejected plume from a room window and its heat flux imposing upon the facade wall. Based on a 1:8 cubic model and Froude modeling, a series of reduced scale experiments are set up. The window dimensions and total heat release rate due to a room fire are changed during experiments. The eave upon the facade wall, made of noncombustible fiber board is installed horizontally above the window top, varying with different vertical heights (distance of the eave to the window top) and lengths (direction normal to the facade wall). The facade flame height is recorded by a CCD camera, while the heat fluxes imposing upon the facade wall are collected by five water-cooled heat flux gauges. Results show that the ejected flame with horizontal eave can be distinguished into the "free flame stage", the "flame horizontal spread stage" and the "flame overflow stage". The visible flame height and heat flux within the "flame overflow stage" are detailed discussed, revealing the physical mechanism of the vertical height and length of the horizontal eave effects. Finally, an implicit correlation in regarding with the visible flame height, the updated flame extension area beneath the horizontal eave as well as the vertical height of the horizontal eave to the window top is established. Taking the horizontal eave conditions into consideration, the heat flux correlation is well corrected and proposed. The results would provide theoretical basis for the fire-induced thermal protection in high buildings. [ABSTRACT FROM AUTHOR]

Abstract The accidental leakages of combustible fuel during storage and transportation cause the pool fires which impose hazardous heat on the nearby occupants and facilities mainly by thermal radiation. This paper presents a new semi-empirical radiation model, namely, the multi-layer cylindrical flame model to predict the radiant heat flux field of pool fires. As the centerline temperature of pool fire varies significantly with vertical height, a formula is proposed to characterize the vertical profile of flame surface emissive power with which the new model can predict the radiant heat flux. The reasonable layer number (the number of small cylinders used for model prediction) can be determined using sensitivity analysis. Comparisons with the experimental data of methanol, heptane, toluene and propane pool fires of different pool diameters indicate that the new radiation model can give a good prediction on the thermal radiation in both horizontal and vertical directions, in spite of fuel type and pool diameter. In comparison with the point source model and three typically single cylindrical flame models, the new radiation model seems to give encouraging results relative to the validity of model system. Sensitivity analysis is also conducted to rank the importance of model parameters. [ABSTRACT FROM AUTHOR]

Abstract Previous studies have usually focused on an ordinary single tunnel fire. However, the structural effect of metro connected tunnel area on the smoke temperature still needs to be clarified. Therefore, this paper aims to modify the current model for predicting the fire-induced smoke temperature considering different sloped conditions in main and connected tunnels. Small-scale and full-scale experiments were conducted with the main tunnel and connected tunnel being horizontal, then extended numerical simulations were performed to clarify the common inclined effect of both the main and connected tunnel on the smoke temperature under natural ventilation. The results show that, maximum smoke temperature varies with a reduction or enhancement of the heat accumulation caused by slope conditions in both the main and connected tunnels. The dimensionless temperature profiles along the smoke spread depends on the slopes of current tunnel itself and are affected little by slopes of another connected one. Prediction models for the maximum smoke temperature and longitudinal temperature profiles were further developed by taking the main and connected tunnel slopes into account. Moreover, it performs good fitting degree for the correlated temperature profile and the predicted maximum smoke temperature agree well with experimental and simulated results, which provides an easy-to-use method for estimating smoke temperature in a fire prevention design or emergency rescue in such metro system. Highlights • Reduced-scale, full-scale experiments and numerical simulations are carried out. • Smoke temperature beneath ceiling in metro tunnel connected area is studied. • Effect of both the main and connected tunnel slopes on smoke temperature is analyzed. • Modified prediction model for smoke temperature in metro connected tunnel area is proposed. • The correlations show good fitting degree and well validated with experiments and simulations. [ABSTRACT FROM AUTHOR]

• Investigation of the liquid pyrolysis model. • Adequate modelling of pool fires using Fire Dynamics Simulator (FDS). • Validation of FDS for pool fires from typical commercial fuels. • Influence of the dynamic Smagorinsky model in the fire behaviour. This paper attempts to evaluate how the Fire Dynamics Simulator (FDS) correlates with experimental flame heights and temperature profiles around a small scale pool fire. Experimental studies were conducted in a 6 cm diameter burner inside an exhaustion hood with three liquid fuels largely used in industry: commercial hexane, hydrous ethanol and type C gasoline. The simulated fuels were defined as mixture of molecules from FDS fuel library. The burning rates were prescribed in the calculation routine and compared with the results when the burning rate is predicted by the simulator. FDS predicts flame heights with errors below 16% when the burning rate is prescribed as boundary condition. Good agreement with experimental data is observed for a given number of probe locations. However, FDS struggled to describe the temperature profile around the flame area in the region close to the pool rim, between X/D = 0.25 and X/D = 0.75, and with heights below 5.0 diameters. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a coupled fire-structure model combining the finite volume and finite element methods, which captures the essential physics of the problem has been developed. The model is based on a multi-physics framework where the essential physics pertaining to the combustion process of the fire and resultant thermo-mechanical response of the structure, in particular, of natural fibre reinforced composites, has been incorporated. In addition, a relatively new concept of adiabatic surface temperature has been introduced as a practical means to transfer data between fire and thermal/structural models at the gas-solid interface. The model predicts the temperature, stress distribution and deformation behaviour of composite beams under combined thermal and mechanical loads. [ABSTRACT FROM AUTHOR]

Abstract In this paper, comprehensive experimental and numerical analyses are carried out to compare the fire reaction properties of wool and flax based polypropylene composites under horizontal and vertical orientations. Moreover, extensive numerical analysis results on the fire reaction properties, burn time and surface temperature distribution have been reported. Fire Dynamics Simulator (FDS®) was employed to develop a numerical predictive model for the cone calorimeter. The study revealed that vertical samples ignited later compared to the horizontal ones. In addition, it has been shown that fibre type has a significant effect on the heat release rate in horizontal and vertical tests. The surface temperature distributions showed similar trends for both composites. [ABSTRACT FROM AUTHOR]

Abstract The paper presents a detailed modelling approach of liquid pool evaporation that is suitable for pool fires and which relies on a combination of mass and heat transfer-based models. The mass transfer approach is based on the so called 'film theory' where mass diffusion is driving the molecular transport process across the film thickness. This driving mechanism is dominant during the early stages of the fire. However, as the liquid surface approaches the boiling point, heat transfer takes over and the evaporation rate becomes controlled by the heat fluxes at the liquid surface. In order to illustrate the potential of the proposed 'comprehensive approach', an in-house code has been developed and validated against a standardized experimental test for the vaporization rate of water in the ASTM E2058 fire propagation apparatus under an external heat flux of 50 kW/m2. The results show that, when the film thickness is calculated assuming a natural convection regime instead of a turbulent forced convection regime, the prediction of the early stage of the vaporization process is significantly improved in comparison to previously published results. However, the water evaporation case appeared to be solely driven by mass transfer (i.e., water vapor concentration gradients). Therefore, additional illustrative numerical tests with several liquid fuels and higher heat fluxes have been carried out. These tests point out the importance of combining the mass transfer-based approach with the heat transfer-based approach when the liquid surface reaches the boiling point. Highlights • A 'comprehensive approach' is proposed for liquid pool evaporation, combining heat and mass transfer-based modelling. • An in-house code is developed and validated using a standardized experimental water vaporization test. • Better results are obtained with natural convection correlations as opposed to forced turbulent convection. • The potential of the 'comprehensive approach' is demonstrated for several liquid fuels. [ABSTRACT FROM AUTHOR]

Fire incidents at fuel storage tank farms are high risk incidents due to the fact that can result in severe socio-economic losses, injuries, deaths and have a serious environmental impact. In the case of a tank fire, there is a serious possibility that the fire will spread to adjacent tanks. The research activity in this area is mainly focused on the prediction of the heat transfer characteristics of pool fires, the thermal response of neighbouring tanks (or target tanks) and the potential of fire spreading. On the contrary, the research for the structural integrity of tanks involved in pool fire scenarios is limited. This paper aims to study the thermal buckling behaviour of fixed-roof tanks in the case of pool fire scenarios, considering one or more burning tanks. To this end, different scenarios are examined, aiming to study the key factors (the burning fuel, the wind, the separation distance between tanks and the size of the burning tanks) that may affect the thermal buckling response of the target tanks. Semi-empirical models, available in the literature, are used for the calculation of the characteristics of flames that arise from burning tanks. Then, the problem is solved numerically, through the Finite Element Method. The heat transfer from the burning tanks to the target tank is treated through the open cavity option, and the response of the target tank is predicted in the same thermo-mechanical analysis. The basic objective is the investigation of the inherent fire resistance of thin-walled tanks and to predict their failure. [ABSTRACT FROM AUTHOR]

Abstract Localized strong winds were observed in the Central Meteorological Observatory (CMO) in Tokyo under big fires after the Great Kanto Earthquake in September 1923. As the CMO buildings were threatened and caught by fire, wind speed exceeded 15 m/s under high temperature reaching 40 °C, while temperature remained below 30 °C and wind speed was less than 5 m/s at a site distant from fires. Strong winds were also observed in extensive fires due to an air attack in World War II in May 1945. This article outlines the meteorological facts in the two cases as examples of fire-induced strong winds. Highlights • The paper describes two cases of strong winds observed in big fires in central Tokyo. • The strong winds were apparently induced by the fire with unusually high temperature. • The strong winds lasted for hours with an almost constant direction during the fire. [ABSTRACT FROM AUTHOR]

Abstract This paper provides a report of the discussions held at the first workshop on Measurement and Computation of Fire Phenomena (MaCFP) on June 10–11 2017. The first MaCFP workshop was both a technical meeting for the gas phase subgroup and a planning meeting for the condensed phase subgroup. The gas phase subgroup reported on a first suite of experimental-computational comparisons corresponding to an initial list of target experiments. The initial list of target experiments identifies a series of benchmark configurations with databases deemed suitable for validation of fire models based on a Computational Fluid Dynamics approach. The simulations presented at the first MaCFP workshop feature fine grid resolution at the millimeter- or centimeter-scale: these simulations allow an evaluation of the performance of fire models under high-resolution conditions in which the impact of numerical errors is reduced and many of the discrepancies between experimental data and computational results may be attributed to modeling errors. The experimental-computational comparisons are archived on the MaCFP repository [1]. Furthermore, the condensed phase subgroup presented a review of the main issues associated with measurements and modeling of pyrolysis phenomena. Overall, the first workshop provided an illustration of the potential of MaCFP in providing a response to the general need for greater levels of integration and coordination in fire research, and specifically to the particular needs of model validation. Highlights • A report on the 1st workshop organized by the IAFSS Working Group on Measurement and Computation of Fire Phenomena (MaCFP). • A focus on validation of fire models based on Computational Fluid Dynamics (CFD). • A first suite of experimental-computational comparisons corresponding to an initial list of target experiments. • A discussion of the importance of grid resolution and a novel description of computational grid design. • A review of current issues associated with measurements and modeling of pyrolysis phenomena. [ABSTRACT FROM AUTHOR]

Beams with web openings represent an attractive system for multi-storey buildings characterized by long spans. Openings in web of steel beams enable building services to be integrated within the constructional depth of the floor, thus reducing the total floor depth. This paper employs the general finite element software ABAQUS to numerically model the behaviour of restrained structural subassemblies of steel beam with web openings to concrete filled tubular column under fire loading scenarios. Steel beams, in this case, are axially restrained which results in a drastically different behaviour when compared to unrestrained beams. In this research, a comprehensive finite element (FE) study of the behaviour of structural subassemblies of steel beams with openings under fire scenarios is conducted. Four sizes of perforated steel sections with seven different opening configurations are modelled and studied in order to understand the significance of their effects. Moreover, the influence of applied load ratios in addition to the level of axial restraint are examined. Consequently, considerations for the performance of axially restrained perforated steel beams under fire scenarios is provided. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on residual mechanical properties of high strength steels (HSS) after exposure to fire. A test program was conducted to study the post-fire mechanical properties of cold-formed HSS. A total of 41 tensile coupon specimens was extracted from cold-formed tubular sections with nominal yield stresses of 700 and 900 MPa. The specimens were exposed to various elevated temperatures ranged from 200 to 1000 °C and then cooled down to ambient temperature before testing. Stress-strain curves were obtained and the mechanical properties of Young's modulus, yield stress (0.2% proof stress), ultimate strength, ultimate strain and fracture strain of the cold-formed high strength steel materials after exposure to elevated temperatures were derived. The post-fire retention factors that obtained from the tests were compared with existing predictive equations in the literature. The influence of heating rate on post-fire mechanical properties was also investigated. New predictive curves for the determination of residual mechanical properties of HSS after exposure to fire are proposed. It is demonstrated that the proposed predictive curves are suitable for both cold-formed and hot-rolled HSS with nominal yield stresses ranged from 690 to 960 MPa. [ABSTRACT FROM AUTHOR]

Following the present directives for building products, the manufacturers of intumescent paints for fire protection of structural steel typically offer tables for presentation of the product's insulating efficiency showing its dry film thicknesses (DFTs) required to sufficiently delay the defined steel critical temperature. From these tables only the final time of reaching this critical limit is obtained clearly, but the overall time evolution of steel temperature remains unknown. In connection to EC3, these data are only sufficient for the use of a simplified design procedure, mostly the method of critical temperature (MCT). Although of a questionable adequacy for cases of restrained thermal dilatations this method is, thus, often applied regardless of the specifics of the structural assembly. The severity of the error implemented by such a simplification is taken as the principal focus of the paper. In providing an answer, fire test results are presented for 13 different steel members protected by different DFTs of a selected intumescent coating. Then, the time-dependent thermal conductivity of the coating is derived and numerical procedure is composed for obtaining the real fire response of intumescent painted assemblies. The method is implemented into a parametric study. The calculated critical times are compared against the critical times suggested by the MCT revealing the MCT being severely on the unsafe side for some cases. The paper thereby confirms the initial hypothesis that the present way of presenting the fire-protective intumescent paints for structural steel is insufficient and will need to be upgraded in the future. [ABSTRACT FROM AUTHOR]

A potential but infrequently studied hazard is the sequential occurrence of earthquakes and fires. Fire hazards following an earthquake can be significant due to increased likelihood of fires igniting, increased demands on firefighting resources, and potential obstacles to timely response. Increased ignitions and longer burn times can have significant structural impacts on reinforced concrete (RC) structures which are usually considered to have superior performance in a fire. The impact of this fire induced structural damage on the lateral load resistance of RC structures, particularly RC structural walls, is not well understood but may be critical in the event of aftershocks and/or future earthquakes. Given the severity of the consequences of reduced lateral load resistance, it is important for engineers to better understand fire-earthquake hazards in RC walls. This paper presents numerical studies to investigate the impact of fire damage on the lateral load resistance of flexure-controlled RC structural walls, including a parametric study to identify influential wall characteristics. Results indicate that fire damage decreases the load-bearing capacity and the stiffness of RC walls under reversed-cyclic loads. Curvature is shown to be a better indication of fire induced failure. At failure, damage may shift to the web of a wall after fire exposure becomes more severe. Wall characteristics which significantly influence the residual wall response quantities were identified to be wall thickness, boundary element length, and axial load ratio. [ABSTRACT FROM AUTHOR]

Sealing smothering method is an important approach to control large fire in channels. This paper experimentally studied the fire behaviors after the sealing in a reduced-scale channel model, considering different initial sealing time under different sealing rates. A series of characteristic parameters, such as the temperature over fire source, mass loss rate of fuel, CO concentration at channel entrance as well as smoke temperature at channel entrance were measured. The results showed that for complete sealing, the earlier the initial sealing time is, the better the fire can be suppressed with a shorter burning duration and lower temperature. However, for incomplete sealing, although the sealing implemented before violent burning stage can reduce the temperature effectively, it causes a much longer burning duration and induces a higher CO concentration at the channel entrance. Especially during violent burning stage, the sealing not only does not restrict fire growth but also exacerbates the channel fire with an extremely high CO concentration at the channel entrance and a longer ceiling flame jet. Besides, as long as one of the channel entrances is not sealed completely, the temperature above the ceiling at channel entrance increases immediately after the sealing, which should be noticed for firefighters during fire rescue. [ABSTRACT FROM AUTHOR]

This paper explains the spatial variation of the fire metrics throughout SE France which was divided into three regions, each characterized by environmental and socio-economic trends. The most deleterious causes were identified as well as their evolution throughout the year. Using the regional fire database Prométhée, which has gathered information on wildfires in SE France since 1973, different fire metrics such as occurrence, burned area have been investigated in the study area. A general trend was identified in SE France showing that most fires occurred and had the highest impact, in terms of burned area, in summer. When the fire causes were known (only 33.7% of the total ignitions), undetermined arson and negligence during professional work were the most frequently involved. However, because of the interactions between region, season, and cause, the fire metrics could differ from this trend, varying spatially and seasonally according to their cause. Fires due to deliberate causes (especially undetermined arson) were concentrated and impacted mainly region 3 in summer, usually presenting a large mean burned area. In contrast, unintentional fires due to forestry and agricultural works were gathered and had a higher impact mainly in region 1 in winter, and fires due to private work, smaller in size, presented the same pattern but occurred mainly in spring in region 3. This pattern was mainly due to the seasonality of these works. The spatio-seasonal variation of natural (lightning) and accidental fires (especially due to power lines and garbage dumps) were mainly driven by climate conditions (regarding lightning and power lines) and/or population density (regarding garbage dumps). When fires smaller than 1ha were removed from the analyses, results could differ regarding the region or season of maximum occurrence and/or mean burned area for fires due to lightning, professional works and negligence during leisure activities. Locating the hotspots of fire occurrence for the main causes will help to improve fire prevention in better allocating law-enforcement and educational measures. [ABSTRACT FROM AUTHOR]

This paper focused on analyzing the Hsuehshan Tunnel Fire in Taiwan, which occurred from a bus fire in the afternoon of May 7, 2012 and caused two death and 34 injuries. Major object damages were reviewed and CCTV records were investigated toward understanding the fire temperature, smoke layers and situations of people in the tunnel refuge area ( Fire Scenarios Analysis & Egress/Rescue Strategies of the 2012 Hsuehshan Tunnel Fire in Taiwan, MOTC, Taiwan, Jan., 2016. ). Data collected from the fire scene were fed into fire scene reconstruction using CFD method (i.e., Fire Dynamics Simulators - FDS). It reveals that the fire temperature reached 800–900 °C and HRR was around 25–30 MW, which are consistent with the reviews of the incident and experiment data. Moreover, the fire temperature obtained from the CFD method when compared with experiment data is more reasonable. It is considered lift-threatening in terms of visibility, temperature and radiant heat flux for both road users and self-defense fire/rescue team when the fire heat reaches 10 MW. It was also reasoned that the fire spread through exit holes on the bus roof and heat was carried by the ventilation flow, leading to serious damage of lighting objects and cable traps above the bus. This study also suggests that the best option for people encounter tunnel fire is to leave their vehicles immediately and evacuate toward upstream direction of the fire. For those who are in the downstream of the fire, they should use the exit doors on the connection tunnel to escape the incident. [ABSTRACT FROM AUTHOR]

Archival research into episodes of frontier violence in the Kimberley region of Western Australia indicate that the bodies of Aboriginal victims of massacres were frequently incinerated following the event. This paper presents the results of a scientific investigation of a reported massacre at Sturt Creek where burnt bone fragments were identified in two adjacent sites and documents the archaeological signatures associated with the sites. The methodology used to undertake the project brought together three systems of knowledge: the oral testimonies of the descent group originating from a sole adult survivor of the massacre; archival, historical and scientific research. An archaeological survey defined the two distinct sites containing hundreds of fragile bone fragments; a third site was found to be highly disturbed. Scientific investigations included macroscopic and microscopic examination of selected bone fragments by an anatomical pathologist and a zooarchaeologist and X-ray diffraction analysis of sixteen bone fragments. The anatomical pathologist and zooarchaeologist undertook macroscopic and microscopic examinations of selected bone samples to identify morphological evidence for human origin. It was concluded that three bone fragments examined may have been human, and two of the fragments may have been from the vault of a skull. It was concluded that the likelihood of them being human would be strengthened if it was found that the three samples had been subjected to high temperatures. X-ray diffraction analysis of 16 bone fragments provided this evidence. All fragments showed sharp hydroxylapatite peaks (crystallite sizes 9882nm and 597nm respectively) and all had been subjected to extreme temperatures of either 600°C for more than 80h, 650°C for more than 20h, 700°C for more than 4h or 800°C for more than 1h. XRD analyses were also done on bone samples collected from three cooking hearths at three different archaeological sites. It was found that two of the three samples had been exposed to substantially lower temperatures for a short time period. It was concluded that there was strong pathological and archaeological evidence that the bone fragments were human in origin, but that the evidence was not conclusive. This research also identified archaeological signatures for the identification of massacre sites in similar Australian environments and circumstances. [ABSTRACT FROM AUTHOR]

Vulnerable groups are found to be over-represented in fire fatalities statistics. In official Norwegian documents vulnerability is described as related to factors such as old age, reduced mobility or cognitive abilities, mental health problems, and substance abuse. As vulnerability to fatal fire is frequently related to residents’ health and life situations, prevention work often exceeds the competencies and responsibilities of the fire department. Cross-sector collaboration is therefore required in order to reach the groups that are at risk. This paper reports from a qualitative interview study with representatives from municipal fire services, property management, housing administration, health and social care. The study explores the challenges experienced by service providers in achieving cross-sector collaboration on fire prevention for vulnerable groups. The findings describe challenges at three levels: 1) the national regulatory level represents an obstacle to local cross-sector collaboration, 2) the municipal level lacks strategies and arenas for cross-sector collaboration for fire safety, and 3) the professional level experiences conflicting values and norms, including uncertainties about professional boundaries. Organizational measures that support the fire services in their efforts to reach vulnerable groups must be targeted to all three levels and go beyond the boundaries of the fire services. The study contributes with a social scientific approach to fire prevention and contributes with new perspectives on fire safety for vulnerable residents. [ABSTRACT FROM AUTHOR]

This paper illustrates a study conducted into the managerial practices implemented to mitigate the consequences of a major fire emergency and to promptly restore normal business operations at a large pediatric hospital. Stemming from prior research on crisis response and recovery in critical infrastructures, this investigation demonstrates that factors such as the complexity of the underlying stakeholder networks, the vulnerability of the involved actors, and several temporal and spatial constraints, all contribute in hampering the intervention of crisis managers. In these situations, relying on consolidated best practices may enable more rapid response and more adequate recovery. This study adopts a qualitative approach to build a retrospective case study that highlights the crucial issues that healthcare crisis managers are requested to face when exposed to thorny work conditions: presence of numerous actors from the public and the private sector, involvement of organizations with contrasting interests, need for a balance among public health, cost containment and legitimacy, etc. The findings of the present investigation expand the theoretical knowledge on the dynamics that characterize crises occurring at critical infrastructures and provide practical recommendations for healthcare emergency managers to improve their response to, and recovery from, major fire emergencies. [ABSTRACT FROM AUTHOR]

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/m 2 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. [ABSTRACT FROM AUTHOR]

The evaporation of sprinkler droplets is an important phenomenon in fire simulations both for heat removal from the gas and for heat removal from surfaces. In this paper, we address the problems of potential numerical instability and super-saturation that may occur in explicit time integration of the droplet equations. Two novel numerical approaches are developed and evaluated. The first is based on an analytical solution that relaxes the cell composition and temperature toward the equilibrium values. The second method is an implicit solution to the droplet equations. The two approaches are implemented in the Fire Dynamics Simulator (FDS) and verified and validated using both single droplet and practical sprinkler calculations. Ultimately, the implicit approach is deemed the most cost effective for practical fire simulations. [ABSTRACT FROM AUTHOR]

In this paper we perform predictive simulations of liquid pool fires in mechanically ventilated compartments. We show that steady state burning rates are accurately predicted using a detailed model for the liquid phase heat transfer. The effect of lowered oxygen vitiation on the burning rate of pool fires is correctly captured. Simulations were done using the Fire Dynamics Simulator and the experiments considered were conducted in the OECD PRISME project. The main difference between the present study and previous simulation studies is the use of a detailed liquid evaporation model and the direct calculation of the vitiation and thermal environment interactions through the CFD solver. [ABSTRACT FROM AUTHOR]

This paper summarizes the small scale thermal exposure test results of the performance of metallic and polymeric O-ring seals typically used in radioactive material transportation packages. Five different O-ring materials were evaluated: Inconel/silver, ethylene-propylene diene monomer (EPDM), polytetrafluoroethylene (PTFE), silicone, butyl, and Viton. The overall objective of this study is to provide test data and insights to the performance of these O-ring seals when exposed to beyond-design-basis temperature conditions due to a severe fire. Tests were conducted using a small-scale stainless steel pressure vessel pressurized with helium to 2 bar or 5 bar at room temperature. The vessel was then heated in an electric furnace to temperatures up to 900 °C for a pre-determined period (typically 8 h–9 h). The pressure drop technique was used to determine if leakage occurred during thermal exposure. Out of a total of 46 tests performed, leakage (loss of vessel pressure) was detected in 13 tests. [ABSTRACT FROM AUTHOR]

Wildfire episodes are becoming more rampant with global warming and climate change. Every year it causes lot of damage in terms of burnt acres and also impacts the air quality and climate through emission of various trace greenhouse gases. As emissions from large fires increase with time, it is essential to monitor the extent and spatial distribution of such changes that can have both short term and long-term implications in terms of human health and feedback on global radiative forcing. In this paper we have used the vertical profile distributions of some of the key trace gases, from AQUA-AIRS sensor to better understand the impact of wildfires in terms of magnitude, spatial and seasonal distribution. Our study shows the impact of season on fire emission in the planetary boundary layer and the free troposphere and also highlights areas in the continental United States (CONUS) where different trace gas emissions are more preponderant. Overall it successfully demonstrates the applicability of satellite-based sensors for regular monitoring of fire related trace gas emissions. [ABSTRACT FROM AUTHOR]

• In the Amazon, Agricultural fires impair respiratory health but are also needed for subsistence agriculture. • Exogenous variation of wind direction was employed as source for identifying the effect of fire on hospitalizations. • One extra standard deviation on fires increased elderly hospitalization due to asthma in 4% of the bed-days generally demanded. • A trade-off between avoided hospitalizations and nutrition of fire-dependent subsistence farmers was unveiled. • Targeting of non-subsistence fires is advised, what could avoid 28 hospital-days per year. Developing countries by relying on agricultural fires trade respiratory health for cheaper land preparation and greater food security of subsistence farmers. In the Brazilian Amazon, thousands of kilometres of vegetation are annually burned, releasing pollutants that impact the health of 24 million inhabitants. The paper seeks to fill two crucial informational gaps for policy planning, namely, the size of the impact on the most pollution-susceptible groups, i.e., children and the elderly, and the priority locations for health-oriented intervention on fires. A municipal-monthly panel covering ten years of the Amazonian territory was analysed by relying on exogenous and high-resolution wind direction variation to identify the effect of fires on pollution and hospitalizations. This is an unparalleled effort for applying to a large geographical area spanning five million km2 a highly refined identification strategy relying on hourly gridded wind and fire data. As the result, one extra standard deviation of "upwind" fires was estimated to increase asthma-related hospitalization of the elderly in 0.03 days/month, that is, 4 % of the bed-days commonly demanded by such kind of hospitalization, an effect whose size decayed with the distance between fires and hospitals. A policy assessment uncovered the trade-off between respiratory health of the elderly and nutritional health of fire-dependent subsistence farmers, presenting a priority map for tackling the issue with municipal-level interventions. The targeting of non-subsistence fires is advised, what could avoid 28 days of hospitalization per year. It is thus demonstrated that the trade-offs inherent to agricultural fires could be better balanced by evidence-based targeting of fire prevention policy. [ABSTRACT FROM AUTHOR]

The low rate of help-seeking and high rate of suicide completion among men has prompted public health officials to create suicide prevention campaigns that specifically target men. Drawing from data collected as part of a larger study of fire recovery in a rural county in Northern California, this paper utilizes 68 interviews with fire survivors (24 men and 44 women) and 40 interviews with mental health service providers to examine how rural residents interpret this type of campaign. To track patterns of help-seeking over time, I also draw upon 26 follow-up interviews – 20 with fire survivors (7 men and 13 women) and 6 with service providers – conducted one year after the first wave of interviews. In total, 134 in-depth interviews were conducted. This paper also draws on a secondary data source; I conducted content analysis of an internal Health and Human Services Agency focus group report used in the development of a local male-targeted suicide prevention campaign, Captain Awesome. As I show, male-targeted suicide prevention efforts have little salience in rural communities in which treatment resources are limited and stigma abounds. Perceptions about material conditions – i.e., treatment resources being few and far between – contribute to residents establishing a norm of not seeking help. Rural culture which emphasizes self-sufficiency and independence contributes to a pattern of both men and women repeating a narrative that frames men who seek help as weak. While research has identified women as key drivers for men's physical health maintenance, my research suggests that the same pattern might not hold around mental health maintenance in rural settings. In sum, I argue that male-targeted campaigns have limited resonance and efficacy in rural communities where material conditions and cultural narratives create physical and psychological barriers to accessing to treatment. • Male-targeted suicide prevention campaigns have little salience in rural areas. • Perceptions of limited treatment resources contribute to low rates of help-seeking in rural places. • A rural ethos emphasizing self-sufficiency contributes to low help-seeking. • Both men and women residents of rural places reinforce stigma against help-seeking. • Suicide prevention campaigns need to be developed with regional specificity. [ABSTRACT FROM AUTHOR]

Vegetation dynamic processes influenced by fires has represented a scientific topic of great importance because of the environmental impact of fires. The use of satellites to investigate vegetational trends has become quite common for the wide coverage and high spatial resolution of satellite images. In this paper, we study the temporal variability of MODIS Aqua and Terra Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) data acquired from 2000 to 2020 and covering the area burned by Camp Fire (California) in 2018. In 2008 other two fires, the BTU Lightning Complex Fire and the Humboldt Fire burned a large part of the same area. The objective of our study, thus, is the characterization of the time dynamics of MODIS Aqua and Terra NDVI and EVI series of sites affected by one and two wildfires by using the Fisher–Shannon (FS) method that allows to have information about the organization/disorder of the time series in relationship with the vegetation post-fire recovery process. Our results suggest that multiple fires cause a decrease of organization and order of NDVI and EVI, indicating a loss a regularity of their time variation. [ABSTRACT FROM AUTHOR]

Savannas are dynamical systems where grasses and trees can either dominate or coexist. Fires are known to be central in the functioning of the savanna biome although their characteristics are expected to vary along the rainfall gradients as observed in Sub-Saharan Africa. In this paper, we model the tree–grass dynamics using impulsive differential equations that consider fires as discrete events. This framework allows us to carry out a comprehensive qualitative mathematical analysis that revealed more diverse possible outcomes than the analogous continuous model. We investigated local and global properties of the equilibria and we showed that various states exist for the physiognomy of vegetation. Though several shifts between vegetation states appeared to be determined by fire periodicity, we showed that direct shading of grasses by trees is also an influential process embodied in the model by a competition parameter leading to bifurcations. Relying on a suitable nonstandard simulation scheme, we carried out numerical simulations in reference to three main climatic zones as observable in Central Africa. [ABSTRACT FROM AUTHOR]

In this paper a simplified analytical method to assess the ductility demand on connections according to fire resistance requirements is developed on the basis of fundamental structural mechanics principles. An objective is to enable the development of a viable method to allow engineers to take the ductility of connections into account in design practice. Numerical finite element simulations of the single beam model were also performed to validate the simplified analytical model and reveal the important parameters that can influence the ductility demand within the connections. Using both analytical and numerical methods, the principal factors which influence the ductility demand of a connection, such as the span of the connected beam and the required connection strength, are also assessed. It is shown that: 1. The compressive ductility of connections is helpful in reducing the push-out of perimeter columns and the possibility of local buckling of beams. 2. Provision of high tensile deformation capacity allows large deflection in the beam, substantially reduces catenary forces on the connections, and consequently reduces the risk of structural collapse in fire. 3. The ductility demand of the connection is closely related to its stiffness and strength, as well as to the slenderness and load ratio of the connected beam. [ABSTRACT FROM AUTHOR]

This paper investigates the fire performance of highly utilized and eccentrically loaded concrete filled composite columns with slendernesses greater than currently permitted by the simple calculation model in Eurocode 4 Part 1.2. The fire resistance rating was calculated by applying implicit as well as explicit finite element analyses and undertaking sequentially coupled thermal-stress analyses. Initially, published fire tests on concentrically loaded columns as well as columns with a modest load eccentrically ( e / h ≤ 0.25) were analysed with normal (NSC) and high strength concrete (HSC). Following the validation of the numerical model against the test data, a parametric study was undertaken on a composite column using a 400 mm square hollow section with a fixed-pinned boundary condition and a relative slenderness at room temperature of λ ̅ = 0.6 . Load levels η fi,t of 0.47, 0.35 and 0.24 were considered and, using a constant eccentricity of e / h = 0.5, a combination of concentric and eccentric loading was applied to the column, as would occur in practice. The results from the parametric analyses show that the FRR reduces significantly as the bending moment increases on the column. Moreover, although the FRR reduced as the utilization increased, it was found that for highly utilized columns the FRR was less sensitive to changes in the magnitude of the bending moments. [ABSTRACT FROM AUTHOR]

This paper presents an approach for assessing the residual capacity of fire exposed reinforced concrete (RC) beams. The approach involves capturing response of RC beams in three stages, namely, structural response at ambient conditions, thermo-mechanical response during fire exposure, and post-fire residual response after cooling down of beams. Distinct material properties of reinforcing steel and concrete are considered during heating and cooling phase of fire exposure and residual (after cool down) phase of analysis. In addition, relevant load level, specific fire scenarios, boundary conditions, and plastic deformations that develop in a beam during fire exposure are also incorporated in evaluating residual response of fire exposed RC beams. The proposed approach is implemented using a detailed numerical model developed in the finite element computer program ABAQUS. Predictions from the numerical model show good correlation with the response parameters measured in experiments for evaluating residual capacity of fire exposed RC beams. Also, predictions of residual capacity from the finite element analysis are compared with that obtained from simplified sectional analysis based on maximum rebar temperatures consideration. This comparison indicates that the finite element analysis yields more realistic predictions of residual capacity than that predicted from simplified sectional analysis. The applicability of the proposed approach in evaluating residual capacity of fire exposed RC beams is illustrated through a case study. [ABSTRACT FROM AUTHOR]

In this paper we present a computational fluid dynamics model for predicting the heat release rates of liquid pool fires. The model makes use of the one-dimensional heat transfer solver to provide the liquid surface boundary condition for the gas phase solver. The in-depth radiation transport is solved by a one-dimensional radiation transport model together with effective absorption coefficients determined from experimental data. The model accounts for the convective heat transfer in the liquid phase by modifying the thermal conductivity. The model is implemented as a boundary condition in the fire dynamics simulator (FDS). The model is validated by comparing experimental and predicted evaporation rates for water and a range of hydrocarbon fuels. The sensitivity of the results to the modelling assumptions and model input parameters is studied. The in-depth heat transfer appears to have a significant effect on the fire dynamics, except for the peak burning rates, which depend most importantly on the gas phase combustion. [ABSTRACT FROM AUTHOR]

Since the Vreman subgrid-scale model was proposed, different types of flow fields have been used to research the applicability of this model. However, the applicability of the model to a flashover heat flow field simulation and the optimal model coefficient for room fires have not been reported. In this paper, the flashover room fire experiments of different opening sizes (ventilation factor) are conducted in an experimental room of size similar to ISO9705, and the room temperature at typical locations is measured. On the same numerical simulation platform, the room temperature field is simulated numerically using the large eddy simulation based on the Vreman and Smagorinsky subgrid-scale models. When the ventilation factors are 1.932 and 2.178, a Vreman subgrid coefficient of 0.02–0.04 is more applicable to the simulation of the temperature field. Overall, the simulation results of the maximum temperature based on the Vreman subgrid-scale model are slightly better than that of Smagorinsky subgrid-scale model. Moreover, the simulation result of the temperature change according to the time from the Vreman subgrid-scale model is similar to the experimental result. However, near the corner of the door in the room, the numerical simulation results underestimate the maximum flow field temperature in the room’s upper part. When the Vreman subgrid-scale model simulates the temperature field in the room with a subgrid coefficient of 0.04 and a ventilation factor of 2.263, the simulation results are better than the results from the Smagorinsky subgrid-scale model with a subgrid coefficient of 0.2. However, when the ventilation factor is 1.397 and the opening is relatively small, the large eddy simulation result based on the Vreman subgrid-scale model with a subgrid coefficient of 0.04 is worse than the results based on the Smagorinsky subgrid-scale model with a subgrid coefficient of 0.2. [ABSTRACT FROM AUTHOR]

This paper demonstrates the need for structural fire engineering in the design and specification of unusual structural arrangements. It is found that the required fire resistance of a structure cannot necessarily be achieved by considering only the fire resistance of individual elements of structure. A case study of columns that have a change of direction over their height (geometrically bi-linear columns) is used to illustrate how unusual arrangements may lead to early failure of key structural elements – even where design guidance is followed. These arrangements are parameterised to allow the relative importance of a number of key variables to be studied. A methodology is developed to estimate the required limiting temperature for the governing elements of the assembly in order to deliver the required performance. [ABSTRACT FROM AUTHOR]

Concrete filled steel hollow structural (CFS) sections are an increasingly popular means to support large compressive loads in buildings. Whilst the response of unprotected CFS sections during a fire is reasonably well researched, their post-fire residual structural performance is less well established. A better understanding of the response of fire-damaged CFS columns is needed to enable better performance-based structural fire engineering of buildings incorporating CFS sections. This paper presents post-fire residual compression tests on unprotected and protected CFS columns along with control tests on six unheated sections. The tests confirm that as the maximum exposed temperature within the cross-section increases, the residual strength capacity, ductility and axial–flexural stiffness decrease. The data are subsequently used to assess the ability to predict the residual capacity of CFS columns after fires, using available post-fire material models and in-fire and ambient structural models. [ABSTRACT FROM AUTHOR]