Wildland fires are a type of vegetation fire that burn in a rural or wild landscape and affect many countries worldwide. They are an important mechanism in ecosystem maintenance, although in certain cases wildland fires can adversely affect both people and the environment. A wildland fire can interact with the surrounding topography, vegetation and weather in a complex manner, which makes microscale prediction of wildland fire behaviour difficult in many situations. This thesis focused on the application of the Weather Research and Forecast (WRF) numerical weather prediction (NWP) and WRF-Fire coupled atmosphere-fire models to investigating aspects of atmospheric interactions with wildland fire. The research covered a wide range of atmospheric scales, from a seasonal mesoscale analysis of fire weather conditions across New Zealand to a microscale analysis of complex atmosphere-fire interactions over idealised terrain. The first study investigated the suitability of WRF modelling of fire weather conditions for the 2009/10 wildland fire season in New Zealand. The WRF model horizontal grid spacing was 8 km and the model output was directly compared with near-surface fire weather conditions meaured and derived at 23 weather stations located throughout New Zealand. The analysis considered the air temperature, relative humidity, wind conditions, rainfall and the New Zealand Fire Weather Index (FWI) and Continuous Haines Index (CHI) on observed high-end fire weather days. WRF typically underpredicted the air temperatures and relative humidities, whereas it typically overpredicted the wind speeds, CHI and the number of high-end fire weather days. WRF was assessed to be unsuitable for accurately modelling particular aspects of fire weather, such as the wind speed and direction, in mountainous terrain and near complex coastlines. Further research is needed to investigate how varying the horizontal resolution in WRF affects the assessed accuracy of modelled fire weather conditions. The second study investigated the behaviour of the Haines Index (HI), CHI and FWI, and their associated atmospheric properties for the 2009/10 wildland fire season in New Zealand. The analysis demonstrated that there was a large degree of spatial variability in fire weather conditions throughout New Zealand, particularly in or near mountainous terrain. The fire weather severity was highest in the eastern South Island and appeared to be closely associated with mesoscale atmospheric processes over mountainous terrain, although the relationship between these atmospheric processes and fire weather condi- tions requires further investigation. The HI and CHI were both limited in their utility at measuring aloft fire weather conditions in high altitude regions. Finally, the fire weather conditions associated with the 36 largest wildland fires of the fire season were evaluated, although no statistical relationships were found between the wildland fire size and either the CHI or FWI. The third study investigated the fire weather conditions across the South Island associated with an extreme foehn event on 6 February 2011. Mountain waves developed in the northwesterly synoptic flow over the Southern Alps and were found to directly influence the fire weather conditions near the surface and aloft in the lee of the mountains. A hydraulic jump along the foothills of the Canterbury Plains resulted in a downslope windstorm with wind speeds exceeding 80 km/h. Further south, large amplitude mountain lee waves directly influenced the near-surface wind speeds and atmospheric stability aloft. The foehn winds were associated with peak air temperatures over 35˚C in the eastern South Island, which are significantly higher than the climatological average. The FWI indicated widespread extreme near-surface fire weather conditions in the lee of the mountains. The subsequent passge of a cold front on 7 February brought a marked reduction in fire weather severity across the South Island. The fourth study investigated atypical wildland fire behaviour on steep leeward slopes through a series of idealised WRF-Fire simulations. The analysis considered both the leeward flow characteristics over a triangular ridge line and the fire spread from an ignition point at the base of the leeward slope. The fire spread was modelled for two different fuel types and with two-way atmosphere-fire coupling both enabled and disabled. The modelled fire spread in the heavy fuel type with coupling enabled closely resembled the fire channelling wildland fire behaviour phenomenon. The initial fire spread was initially dominated by upslope fire spread to the mountain ridge line at an average rate of around 2.0 km/h. This was followed by a phase of intermittent rapid lateral fire spread close to the ridge line at a maximum rate of around 3.6 km/h. The intermittent rapid lateral fire spread was driven by strongly circulating horizontal near-surface winds that were associated with updraft-downdraft interfaces. These updraft-downdraft interfaces formed due to an interaction between the strong pyro-convection and terrain-modified winds. The presented research collectively demonstrated the versatility and effectiveness of NWP and coupled atmosphere-fire modelling for studying various aspects of atmospheric interactions with wildland fire. The research further highlighted the effects of atmospheric processes over complex terrain on fire weather conditions and wildland fire behaviour. Although three of the studies in the thesis had a regional focus on New Zealand, the research outcomes should benefit end users in fire management worldwide.

A study was undertaken to characterize two dynamic fuel types not included in the Canadian Forest Fire Behaviour Prediction System: forested bogs and blowdown. Fuel load and structure were measured at ten forested bog sites in central Alberta along a 108 year post-fire chronosequence. Canopy bulk density increased following a sigmoidal curve between 0.00 and 0.54 kg•m-3. Crown fire potential was modeled using a general crown fire behaviour model and found to follow a similar sigmoidal pattern increasing with time-since-fire. Blowdown fuel loads were measured at six sites in northwestern Ontario and ranged from 13.4 to 18.9 kg•m-2. Elevated fine blowdown fuels were found to have faster reaction times and dry more rapidly than predicted by the Fine Fuel Moisture Code. Detailed observations were also made of fire behaviour in blowdown fuels

A study was undertaken to characterize two dynamic fuel types not included in the Canadian Forest Fire Behaviour Prediction System: forested bogs and blowdown. Fuel load and structure were measured at ten forested bog sites in central Alberta along a 108 year post-fire chronosequence. Canopy bulk density increased following a sigmoidal curve between 0.00 and 0.54 kg•m-3. Crown fire potential was modeled using a general crown fire behaviour model and found to follow a similar sigmoidal pattern increasing with time-since-fire. Blowdown fuel loads were measured at six sites in northwestern Ontario and ranged from 13.4 to 18.9 kg•m-2. Elevated fine blowdown fuels were found to have faster reaction times and dry more rapidly than predicted by the Fine Fuel Moisture Code. Detailed observations were also made of fire behaviour in blowdown fuels

Yes / Steel-concrete composite structures are commonly used in buildings and bridges because it takes advantage of tensile strength of steel and compressive strength of concrete. The two components are often secured by shear connectors such as headed studs to prevent slippage and to maintain composite action. In spite of its popularity, very little research was conducted on steel-concrete composites particularly on headed stud shear connectors in regards to its post-fire behaviour. This research investigates the post-fire behaviour of innovative shear connectors for composite steel and concrete. Three type of connectors were investigated. They are headed stud shear connectors, Blind Bolt 1 and Blind Bolt 2 blind bolts. Push-out test experimental studies were conducted to look at the behaviour and failure modes for each connector. Eighteen push tests were conducted according to Eurocode 4. The push test specimens were tested under ambient temperatures and post fire condition of 200˚C, 400˚C and 600˚C. The results in ambient temperature are used to derive the residual strength of shear connectors after exposing to fire. Findings from this research will provide fundamental background in designing steel-concrete composites where there is danger of fire exposure.

This research investigates the decomposition and burning behaviours of polyurethane foams experimentally and compares the experimental results obtained with the numerical results from the pyrolysis model of Fire Dynamics Simulator, Version 5 (FDS 5). Based on the comparison of model and experimental heat release rates, the accuracy of the pyrolysis model is quantified. In total, this research tested seven polyurethane foams consisting of three non-fire retardant (NFR) and four fire retardant (FR) foams. According to the simultaneous differential scanning calorimetry and thermogravimetric analysis (SDT) experiments, the decomposition behaviour of polyurethane foams under nitrogen environment is represented by two pyrolysis reactions. The first reaction consists of foam decomposition into melts and gases while the second reaction consists of the decomposition of the remaining melts into gases. The kinetic properties which govern the rate of decomposition are the activation energy (E), pre-exponential factor (A), reaction order (n) and heat of reaction (Δhr). Using graphical techniques, E, A and n of the first and second reactions are determined from the thermogravimetric analysis (TGA) results. Through analysing the differential scanning calorimetry (DSC) results, Δhr is determined from the changes in heat flow and sample mass. The thermophysical properties govern the heat transfer through material and these are the thermal conductivity (λ) and specific heat (cp) which are measured experimentally at ambient temperature through the Hot Disk method. Through the Sample Feeding Vertical Cone, the decomposition and melting behaviours of polyurethane foams in a vertical orientation are investigated and the foams tested can be categorised into those which produce melts only after ignition and those which produce melts and char after ignition. The 1-dimensional burning behaviour of foams is obtained from the cone calorimeter experiments. The NFR foams show a change from plateau burning behaviour at low heat flux to two stage burning behaviour at high heat flux while the FR foams consistently show two stage burning behaviour. The combustion property governs the amount of heat released when fuel combusts and this is the effective heat of combustion (Δhc,eff) which is determined from the heat released and mass consumed in the cone experiment. The 1-dimensional burning behaviour is simulated using the pyrolysis model of FDS 5 and two different modelling approaches are considered. The direct method uses the material properties determined experimentally as FDS 5 inputs while the refined method uses the genetic algorithm of Gpyro to refine the kinetic properties which are later used as FDS 5 inputs. The heat release rate of the model and experiment are compared through linear regression analysis which quantifies the accuracy of both methods. The accuracy is defined as the percentage of data points within the boundary of acceptance which is bounded by 25 % of the greatest experimental heat release rate. This assessment method places greater emphasis on the accuracy of developed burning phases and lesser emphasis on the accuracy of initial growth and final decay. The accuracy of the direct method is found to be 56 % while the refined method with estimated kinetic properties achieves a higher accuracy of 75 %. The 2-dimensional burning behaviours are investigated in the foam slab experiments for two different slab thicknesses, 120 and 100 mm. The opposed-flow spread of 120 mm slab is more intense and rapid while for the 100 mm slab, the flame spread is less intense and slow. FDS 5 is used to simulate the experimental results but when the material properties either developed experimentally or refined by Gpyro are used as inputs, the model fails to produce flame spread. This is because FDS 5 does not yet have the features which address the dynamics of foam melting and the reactive nature of the flame. In order to produce flame spread in the model, E of the reactions have been reduced to increase the decomposition rate.

La câblerie est un secteur industriel gros consommateur de polymères. Dans ce domaine, les normes imposent cependant de limiter le risque incendie et donc d'ignifuger les matériaux polymères utilisés, sources importantes de combustibles. De nombreux travaux ont porté sur leur ignifugation par utilisation d'additifs retardateurs de flammes, mais peu d'entre eux ont étudié l'influence de la morphologie des mélanges polymères chargés sur la stabilité thermique et le comportement au feu. Cette thèse fait suite à un précédent projet qui avait démontré une influence significative de la morphologie sur le comportement au feu d'un mélange polymère binaire (PC/PBT). Elle a pour but d'améliorer la compréhension de cette influence dans le cas de formulations plus complexes (ternaires ou quaternaires) à matrice éthylène méthylacrylate (EMA). Pour cela, la première stratégie adoptée a été l'identification d'un système ignifugeant comprenant un polyester capable de charbonner lors de l'ajout d'un RF. Une fois ce système identifié (PBT+MDH), il a été incorporé en matrice EMA en faisant varier la composition et la morphologie (dispersion sélective, taille des particules…). Cette approche a mis en évidence des différences significatives entre les différentes formulations et des résultats très intéressants ont été obtenus en termes de réaction au feu à l'échelle laboratoire. Cependant, le passage à l'échelle pilote (test de propagation de flamme) n'a pas permis de valider ces formulations pour des applications câbles. Au vu de ces constatations, une dernière partie a été proposée pour essayer d'améliorer la cohésion du résidu par ajout de polyphosphate d'ammonium. / The cable industry is a major consumer of industrial polymers. In this area, the standards impose to limit the fire risk and thus to enhance the fireproof of the polymeric materials which are important sources of fuel. Many studies have focused on their flame retardancy by using additive flame retardants, but few of them have studied the influence of the morphology of filled polymer blends on the thermal stability and the fire behavior. This thesis follows a previous project which demonstrated a significant influence of the morphology on the fire behavior of a binary polymer blend (PC / PBT). It aims to improve the understanding of this influence in the case of more complex formulations (ternary or quaternary) with ethylene methylacrylate (EMA) matrix. The first strategy was the identification of a flame retardant system including polyester that is able to char when a flame retardant is added. Once the system is identified (PBT + MDH), it was incorporated in EMA matrix by varying the composition and the morphology (selective dispersion, particle size ...). This approach showed significant differences between the different formulations and very interesting results have been obtained in terms of fire reaction at the laboratory scale. However, the scale-up approach (flame spread test) did not validate these formulations for cables applications. Therefore, the last part has been proposed to try to improve the cohesion of the residue by adding ammonium polyphosphate.

Composite slab flooring systems for steel-framed buildings consist of a profiled steel deck and a cast in-situ slab. The slab traditionally includes a layer of light gauge steel mesh reinforcement. This mesh is placed near the surface, which controls the early-age cracking caused by concrete drying and shrinkage. The steel mesh also performs a vital structural role at high temperatures. Structural fire tests and numerical investigations over the last 15 years have established that the mesh can provide enhanced fire resistance. A load-carrying mechanism occurs in fire with the mesh acting as a tensile catenary, spanning between perimeter supports. This structural mechanism is currently utilised regularly in the performance-based fire engineering design of steel-framed buildings. In a recent development, this mesh can be removed by using concrete with dispersed polymer fibre reinforcement to form the composite slab. The polymer-fibre-reinforced concrete (PFRC) is poured onto the deck as normal, and the fibres resist early crack development. For developers this technique has several advantages over traditional reinforcing mesh, such as lower steel costs, easier site operations and faster construction. However, to date the fire resistance of such slabs has been demonstrated only to a limited extent. Single element furnace tests with permissible deflection criteria have formed the basis for the fire design of such slabs. But these have not captured the full fire response of a structurally restrained fibre-reinforced slab in a continuous frame. The polymer fibres dispersed throughout the slab have a melting point of 160ºC, and it is unclear how they contribute to overall fire resistance. In particular, there has been no explanation of how such slabs interact with the structural perimeter to maintain robustness at high deflections. This project was designed to investigate the structural fire behaviour of restrained polymer-fibre-reinforced composite slabs. An experimental series of six slab experiments was designed to investigate the effects of fibre reinforcement and boundary restraint. A testing rig capable of recording the actions generated by the heat-affected slab was developed and constructed. Model-scale slab specimens were tested with different reinforcement and perimeter support conditions, to establish the contributions to fire resistance of the polymer fibres and applied structural restraint.

No / This paper presents the results of a simulation study of 10 fire tests on restrained steel beam–column assemblies using five different types of joints: fin plate, flexible endplate, flush endplate, web cleat and extended endplate. This paper will provide details of the simulation methodology for achieving numerical stability and faithful representation of detailed structural behaviour, and compare the simulation and experimental results, including joint failure modes, measured beam axial forces and beam mid-span deflections. Good agreement between ABAQUS simulations and experimental observations confirms that the finite element models developed through the ABAQUS/Standard solver are suitable for predicting the structural fire behaviour of restrained structural assemblies with realistic steel joints undergoing different phases of behaviour in fire, including restrained thermal expansion and catenary action in the beams. The validated model may be used to conduct numerical parametric studies to generate theoretical data to help develop detailed understanding of steel joint behaviour and their effects on robustness of steel framed structures in fire.

In recent years, a number of high profile accidental fires have occurred in several road and rail tunnels throughout the world. Many of these fires grew rapidly to catastrophic size and claimed many lives. The processes involved in the rapid growth and extremely severe of these fires are not adequately understood as yet. The introduction to this thesis reviews a number of these accidental fires and describes much of the previous experimental research which has brought about the current understanding of tunnel fire behaviour. A detailed review of the relevant parts of elementary fire dynamics is also presented. This thesis addresses two main questions: 1. What is the influence of longitudinal ventilation on fire size in tunnels? and 2. What is the influence of tunnel geometry on fire size? The answers to both these questions are determined using a probabilistic method called Bayes Theorem. This provides a method of answering the above two questions using the handful of experimental data which are available. It is found that the heat release rate (HRR) of a heavy goods vehicle (HGV) fire may be greatly increased in magnitude by longitudinal ventilation, for example by about a factor of 5 with a longitudinal ventilation velocity of 3ms-1. It is also found that longitudinal ventilation may cause a significant increase in the HRR of large pool fires, but may cause a decrease in the HRR of small pool fires and car fires. An equation is derived to predict the influence of tunnel geometry on HRR. It is found that HRR varies principally with the width of the tunnel and the width of the fire object. The HRR of a fire in a tunnel my be increased up to four times due to the geometry of the tunnel.

Le comportement au feu de matériaux polymères peut changer plus ou moins fortement après vieillissement, mettant en péril les biens et les personnes en cas d’incendie. Ces changements dépendent du système considéré (nature du système retardateur de flamme, de la matrice polymère) et des conditions de vieillissement. Or jusqu’à aujourd’hui, les normes exigent l’évaluation de la réaction au feu d’un matériau juste après fabrication et rarement après un vieillissement représentatif des conditions réelles d’utilisation. L’évolution des caractéristiques des polymères ignifugés au cours du temps est actuellement peu connue, et seules quelques études ont eu lieu à ce sujet. Le travail de cette thèse concerne donc l’impact du vieillissement sur les performances au feu de systèmes complexes de polymères ignifugés. L’étude est basée sur les polymères polyméthacrylate de méthyle (PMMA) et acide polylactique (PLA) ; le système retardateur de flamme est quant à lui constitué de charges phosphorées et de silicates nanométriques. Un protocole de vieillissement et une méthodologie d’étude ont ensuite été mis en place pour déterminer l’influence du vieillissement sur les propriétés de ces matériaux : morphologie, masse molaire des polymères, dégradation des retardateurs de flamme, comportement au feu. Enfin, les caractéristiques des produits émis en phase gaz au cours de la combustion d’échantillons vieillis et non vieillis ont été analysées / The fire behaviour of polymeric materials can be modified after ageing, possibly leading to severe damages. These modifications depend on the chemical nature of the system (polymeric matrix, flame retardant system) and on the ageing conditions. Currently, norms exist, that define fire properties of fresh flame-retarded materials; but only few studies have been performed on aged materials. The aim of this work consists in evaluating the impact of ageing of flame-retarded materials. Firstly, materials have been processed from various formulations. The study focused on poly(methyl methacrylate) (PMMA) and poly(lactic acid) (PLA) polymers; flame-retardant system combining a phosphorus compound and mineral nanoparticles was added. Then an operating procedure has been created to simulate ageing, and a methodology has been developed to assess the characteristics of the composites before and after ageing (viscosity, morphology, fire behaviour). Finally, the combustion aerosols emitted by unaged and aged formulations have been investigated