Дисертації з теми "Fire safety modelling"

This thesis describes the development of a computer simulation model for the investigation of airliner fire accident safety. The aim of the work has been to create a computer-based analysis tool that generates representative aircraft accident scenarios and then simulates their outcome in terms of passenger injuries and fatalities. The details of the accident scenarios are formulated to closely match the type of events that are known to have occurred in aircraft accidents over the last 40 years. This information has been obtained by compiling a database and undertaking detailed analysis of approximately 200 airliner fire accidents. In addition to utilising historical data, the modelling work has incorporated many of the key findings obtained from experimental research undertaken by the world's air safety community. An unusual feature of the simulation process is that all critical aspects of the accident scenario have been analysed and catered for in the formative stages of the programme development. This has enabled complex effects, such as cabin crash disruption, impact trauma injuries, fire spread, smoke incapacitation and passenger evacuation to be simulated in a balanced and integrated manner. The study is intended to further the general appreciation and understanding of the complex events that lead to fatalities in aircraft fire accidents. This is achieved by analysing all contributory factors that are likely to arise in real fire accident scenarios and undertaking quantitative risk assessment through the use of novel simulation methods. Future development of the research could potentially enable the undertaking of a systematic exploration and appraisal of the effectiveness of both current and future aircraft fire safety policies.

Fire development in a vented enclosure can proceed in an explosive and disastrous manner called flashover. This thesis examines when, why and how flashover occurs and gives the answers in terms of a few determining dimensionless parameters. The mechanism of flashover considered in this thesis is an enhancement of the burning rate because of thermal radiation from a layer of hot smoke, produced in the course of the fire, to the fire bed. A model, which is proposed for the problem, describes the development fro~ the moment of ignition incorporating the traditional two-zone approach. During early fIre development the density and temperature of the lower zone are reasonably assumed to be close to their initial value. Flashover itself is assumed to occur early in the fIre development, within the fuel controlled combustion regime. The model is analysed using the techniques of classical thermal explosion theory. Explicit criteria are found analytically and graphically to determine if the fIre will achieve flashover or not. The temperature-time characteristics of the fIre development are obtained explicitly for the fIrst time. It is shown that the thermal inertia of the compartment walls can have a significant effect upon the development. The effect of geometrically scaling the compartment is considered. Nondimensional analysis makes such study effective and leads to a square root relationship for the temperature/time characteristics of the fire development. The correlation between the model, four prevIOUS models and small scale experiments is examined. Under reasonable assumptions all models are shown to be described by the same mathematical problem. This means that the criterion for flashover and the development characteristics can be used for any of the modified models observed. Results are illustrated for an experimental fire box used in many experiments.

The dynamics of the intrinsically unstable premixed flames propagating in channels is studied by means of numerical modelling in this work. Critical conditions of extinction and the influence of the thermal-diffusive effect on the dynamics of flame propagating in planar channels with cold sidewalls under gravity is investigated. For the horizontally propagating flames, the appearance of inversion influences the effect of thermal-diffusion on the asymmetry of flame fronts. For upwards propagating flames, the convex shape of the flame imposed by the mode of ignition combined with buoyancy can suppress the thermal-diffusive effects; in contrast, the buoyancy alone cannot damp the thermal diffusive effects even for quite large Froud numbers in regard to the appearance of inversion. The variation of Lewis number has no essential effect on the planar flame shape formation when flame propagates downward. Lowering Lewis number can significantly decrease the critical conditions of extinction. However, if Lewis number is smaller than some limit, its further effect on the critical extinction conditions is unsignificant. In the two-step consecutive reaction, the effects of the ratio of Damkohler numbers, heat release rates, activation energy and Lewis number on the separation and fragmentation of flames are considered. The inversion is more pronounced in combustion with separated flame fronts than for single-step reactions. However, the inversion is obvious only when the two flame fronts are close enough to each other. Thus, the details of combusiiition chemistry may have a strong effect on the stability of the flame front. The thermal diffusive effect of the first flame is, in certain way, dominant and has influence on the second flame. The presence of the first reaction suppresses the thermal-diffusive effect of the second reaction in regard to the appearance of inversion. The propagation of flames at a variety of Reynolds number ranging from 70 to 1000 are explored. For longer channels or a flat initial flame front, the inversion of the flame is apparent for Reynolds number higher than 200. For large &, the computational grids should be very fine because of the small thickness of preheat zone. The Generalized Curvilinear Coordinate Gridding method is introduced and an elliptic grid generator based on the variational approach is employed to construct the solution-adaptive grids. However, we found out that the global structure of the algorithm required by the adaptive grid approach might be not as efficient as simplified non-adaptive grids for prospective use of massively parallel computers.

The use of numerical tools in fire safety engineering became usual nowadays and this tendency is expected to increase with the evolution of performance based design. Despite the constant development of fire modelling tools, the current state of the art is still not capable of predicting accurately solid ignition, flame spread or fire growth rate from first principles. The condensed phase, which plays an important role in these phenomena, has been a large research area since few decades, resulting in an improvement of its global understanding and in the development of numerical pyrolysis models including a large number of physical and chemical mechanisms. This growth of complexity in the models has been justified by the implicit assumption that models with a higher number of mechanisms should be more accurate. However, as direct consequence, the number of parameters required to perform a simulation increased significantly. The problem is when the uncertainty in the input parameters accumulates in the model output beyond a certain level. The global error induced by the parameters uncertainty balances the improvements obtained with the incorporation of new mechanisms, leading to the existence of an optimum of model complexity. While one of the first modelling tasks is to select the appropriate model to represent a physical phenomenon, this step is often subjective, and detailed justifications of the inclusion or exclusion of the different mechanisms are infrequent. The issue of how determining the most beneficial level of model complexity is becoming a major concern and this work presents a methodology to estimate the affordable level of complexity for polymer pyrolysis modelling prior ignition. The study is performed using PolyMethylMethAcrylate (PMMA) which is a reference material in fire dynamics due to the large number of studies available on its pyrolysis behaviour. The methodology employed is based on a combination of sensitivity and uncertainty analyses. In the first chapter, the minimum level of complexity required to explain the delay times to ignition of black PMMA samples at high heat flux levels is obtained by exploring one by one the effect on the condensed phase of several mechanisms. It is found that the experimental results cannot be explained without considering the in-depth radiation absorption mechanism. In the second chapter, a large literature review of the variability associated with the main parameters encountered in pyrolysis models is performed in order to establish the current level of confidence associated with the predictions using simple uncertainty analyses. In the third chapter, a detailed analysis of the governing parameters (parametric sensitivity) is performed on the model obtained in chapter 1 to predict the delay time to ignition. Using the ranges obtained in chapter 2 for the input parameters, a detailed uncertainty analysis is performed revealing a large spread of the numerical predictions outside the experimental uncertainty. While several parameters, including the attenuation coefficient (from the in-depth radiation absorption mechanism), present large sensitivity, only a few are responsible for the large spread observed. The parameter uncertainty is shown as the limiting step in the prediction of solid ignition. In the fourth chapter, a new methodology is developed in order to investigate the predominant mechanisms for the prediction of the transient pyrolysis behaviour of clear PMMA (no ignition). This approach, which corresponds to a mechanism sensitivity, consists of applying step-by-step assumptions to the most complex model used in the literature to model non-charring polymer pyrolysis behaviour. This study reveals the relatively high importance of the heat transfer mechanisms, including the process of in-depth radiation. In the fifth chapter, an investigation of the uncertainty related to the calibration of pyrolysis models by inverse modelling is performed using several levels of model complexity. Inverse modelling couples the experimental data to the model equations and this dependency is often ignored. Varying the model complexity, this study reveals the presence of compensation effects between the different mechanisms. The phenomenon grows in importance with model complexity leading to unrealistic values for the calibrated parameters. From the performed sensitivity and uncertainty analyses, the mechanism of in-depth absorption appeared critical for some applications. In the sixth chapter, an experimental investigation on specific conditions impacting the sensitivity of this mechanism shows its large dependency on the heat source emission wavelength when comparing the two heat sources of the most used pyrolysis test apparatuses in fire safety engineering. More fundamental investigations presented in the seventh chapter enabled to quantify this dependency that needs to be considered for modelling or experimental analyses. The impact of the heat source on the radiation absorption (depth and magnitude) is shown to be predictable thanks to the detailed measurements of the attenuation coefficient of PMMA and the emissive power of the heat sources. The global uncertainty associated with the input parameters, extracted either from independent studies or by inverse modelling, appears as a limiting step in the improvement of pyrolysis modelling when a high level of complexity is implemented. A combination of numerical (sensitivity and uncertainty) analyses and experimental studies is required before increasing the level of complexity of a pyrolysis model.

Safety cases must be produced by offshore operators to assess the risks posed to the personnel by potential accidents. On an offshore platform two of the major hazards are fires and explosions resulting from an accidental hydrocarbon release. The overpressures generated during an explosion can threaten the integrity of the platform structure. It is therefore important to be able to estimate the overpressures generated, should an explosion occur, and to predict the frequency of such an event. A methodology has been developed to predict the frequency of explosions of different magnitudes occurring in a module on an offshore platform. This methodology combines established risk assessment techniques, such as event tree analysis and fault tree analysis, with fluid flow modelling. Assumptions have been made in the methodology to simplify the calculation procedure. These assumptions relate to the conditions under which the leak occurs, the build up of gas in air concentration and the probability calculations. Frequency predictions are required to be as accurate as possible to enable the acceptability of the risk to be determined and reduced to a level which is as low as reasonably practicable. Hence each of the assumptions within the methodology has been addressed, to determine a more complete prediction tool. Once an accurate frequency for the explosion occurring has been determined, the risk to personnel must be minimised to an acceptable yet practical level. On existing designs it is impractical to alter the layout of the platform. However the nature of the safety systems may be changed. These safety features include isolation, blowdown, mitigation and detection systems. An optimisation study presents three schemes to identify the optimum configuration of the safety systems, in terms of the overpressures generated, as a means of reducing the risk to the platform.

The ability to predict the temperatures in protected steel structures is of vital importance for the progress of fire safety engineering. Existing methods are limited in several respects, typically being computationally restricted and limited to examination of the performance of specific components. This thesis investigates a generalised CFDbased methodology for thermal analysis of structural members in fire, developed to overcome these limitations. A novel methodology has been developed, known as GeniSTELA (Generalised Solid ThErmal Analysis), which computes a “steel temperature field” parameter in each computational cell. The approach is based on a simplified 1D model for heat transfer, together with appropriate corrections for 2D and 3D effects, to provide a quasi- 3D solution with a reasonable computational cost. GeniSTELA has been implemented as a submodel within the SOFIE RANS CFD code. The basic operation of the model has been verified and results compared to the empirical methods in EC3, indicating a satisfactory performance. The role of the surface temperature prediction has been examined and demonstrated to be important for certain cases, justifying its inclusion in the generalised method. Validation of the model is undertaken with respect to standard testing in fire resistance furnaces, examining the fire ratings of different practical protection systems, and the BRE large compartment fire tests, which looked at protected steel indicatives in full-scale post-flashover fires; in both cases, a satisfactory agreement is achieved. Model sensitivities are reported which reveal the expected strong dependencies on certain properties of thermal protection materials.

In fire, any information about the actual condition within the building could be essential for quick and safe response of both fire–fighters and occupants. In most cases, however, the emergency responders will rarely be aware of the actual conditions within a building and they will have to make critical decisions based on limited information. Recent buildings are equipped with numbers of sensors which may potentially contain useful information about the fire; however, most buildings do not have capability of exploiting these sensors to provide any useful information beyond the initial stage of warning about the possible existence of a fire. A sensor–linked modelling tool for live prediction of uncontrolled compartment fires, K– CRISP, has therefore been developed. The modelling strategy is an extension of the Monte– Carlo fire model, CRISP, linking simulations to sensor inputs which controls evolution of the parametric space in which new scenarios are generated, thereby representing real–time “learning” about the fire. CRISP itself is based on a zone model representation of the fire, with linked capabilities for egress modelling and failure prediction for structural members, thus providing a major advantage over more detailed approaches in terms of flexibility and practicality, though with the conventional limitations of zone models. Large numbers of scenarios are required, but computational demands are mitigated to some extent by various procedures to limit the parameters which need to be varied. HPC (high performance computing) resources are exploited in “urgent computing” mode. K–CRISP was demonstrated in conjunction with measurements obtained from two sets of full–scale fire experiments. In one case, model execution was performed live. The thesis further investigates the predictive capability of the model by running it in pseudo real–time. The approach adopted for steering is shown to be effective in directing the evolution of the fire parameters, thereby driving the fire predictions towards the measurements. Moreover, the availability of probabilistic information in the output assists in providing potential end users with an indication of the likelihood of various hazard scenarios. The best forecasts are those for the immediate future, or for relatively simple fires, with progressively less confidence at longer lead times and in more complex scenarios. Given the uncertainties in real fire development the benefits of more detailed model representations may be marginal and the system developed thus far is considered to be an appropriate engineering approach to the problem, providing information of potential benefit in emergency response. Thus, the sensor–linked model proved to be capable of forecasting the fire development super–real– time and it was also able to predict critical events such as flashover and structural collapse. Finally, the prediction results are assessed and the limitations of the model were further discussed. This enabled careful assessment of how the model should be applied, what sensors are required, and how reliable the model can be, etc.

The move towards performance-based design of the fire resistance of structures requires more accurate design methods. An important variable in the fire performance of timber structures is the in-depth temperature distribution, as wood is weakened by an increase of temperature, caused by exposure to high heat fluxes. A proper prediction of temperature profiles in wood structural elements has become an essential part of timber structural design. Current design methods use empirically determined equations for the temperature distribution but these assume constant charring rates, do not account for changes in the heating conditions, and were obtained under poorly defined boundary conditions in fire resistance furnaces. As part of this research project, a series of experimental in-depth temperature measurements were done in wood samples exposed to various intensities of radiant heat fluxes, with clearly defined boundary conditions that allow a proper input for pyrolysis models. The imposed heat fluxes range from 10 kW/cm 2, which generates an almost inert behaviour, to 60 kW/cm 2, where spontaneous flaming is almost immediately observed. Mass loss measurements for all the imposed heat fluxes were also performed. The second part of this project dealt with the modelling of the pyrolysis process, with an emphasis placed on temperature prediction. The main objective was to identify the simplest model that can accurately predict temperature distributions in wood elements exposed to fires. For this, an analysis of the different terms which have been included by several models in the energy equation has been done, by quantifying its magnitude. Five models with different degrees of simplification have been developed. Comparison with the experimental data has shown that a simple and accurate model of temperature profiles must include the rise in the solid sensible heat, the heat transferred by conduction, the heat of moisture evaporation, the heat of pyrolysis reaction and the effect of char oxidation.

Ce travail, mené conjointement entre CNPP et le Laboratoire d’Énergétique et de Mécanique Théorique et Appliquée, est consacré à la mise en place d’un modèle d’évacuation de personnes, dans l’optique d’une application en Ingénierie de Sécurité Incendie. Le modèle de cheminement de personnes développé dans ce manuscrit est un modèle physique reposant sur une équation de conservation de la densité de personnes. Il est basé sur des hypothèses simples et réalistes résultant de l’observation de mouvements de foule, et utilise une vision macroscopique des personnes caractérisées par une densité moyenne. Ce modèle est mis en œuvre sur des cas de vérification et de comparaison issus de la littérature. Des expériences d’évacuation sont réalisées à échelle réelle afin de récolter des données quantitatives sur le mouvement des personnes et de valider de façon pertinente le modèle de cheminement de personnes. En outre, une stratégie est proposée afin d’intégrer dans la modélisation les contraintes thermiques et optiques liées au feu ainsi que leur impact sur le processus d’évacuation. Enfin, des simulations d’évacuation intégrant les effets du feu sont effectuées sur une configuration à grande échelle
This work was conducted as a collaboration between CNPP and the laboratory LEMTA. It was devoted to the implementation of an emergency egress model offering prospects for use in Fire Safety Engineering. The pedestrian movement model described in this manuscript is a physical model relying on a people density balance equation. This model is based on three fundamental assumptions resulting from pedestrian phenomena commonly observed, especially in crowds. Its mathematical formulation assumes that people are regarded as a mean density in a macroscopic way. The pedestrian model was tested on verification and comparison cases extracted from literature. Evacuation drills were also performed at real scale without fire constraints to collect some quantitative data like egress times or flows, and to validate the people motion model. Furthermore, a mathematical strategy is propounded in order to integrate thermal and optical stresses into the evacuation model and to take into consideration their incidence on evacuation processes. Finally, egress simulations are achieved on a large-scale configuration considering different scenarios involving fires

Safety and Health in the workplace has long been the priority work of the Hong Kong administration but the accidentstatistics in Hong Kong tell another story. No matter how sophisticated a safe system is designed, its ultimate success depends very much on the person who carries out the job. Safe behaviour has therefore become the contemporary study of safety and health at work.Since human behaviour is a multidimensional construct, its understanding requires a multiple theory approach. Inspired by this concept, this study explores a Multi-Dimensional Safe Behaviour Model in explaining Construction Workers' Safe Behaviour. The study examines its implication for management when safe behaviours are to be instilled. Nine psychological theories and models, identified under the perspective of the Intrapersonal, Interpersonal and Community Level are examined. A short list of 9 variables of "Social Norm", "Management Commitment", "Safety Knowledge", "Perceived Risk", "Safety Experience", "Self Efficacy"; "Perceived Consequence", "Chance" and Intention to Behave" was constructed. Three hypothetical constructs of "Social Support", "Attitude" and "Expectance" composed of observable indicators from the nine identified variables are also formed. The variables are then put together into a hypothesised Multi-Dimensional Safe Behaviour Model with the casual relationships between variables identified. A Structural Equation Modelling procedure shows that the hypothesised Multi-Dimensional Safe Behaviour Model fits the data reflecting the necessity of adopting a holistic approach in addressing behavioural issues. "Safety Attitude" is found to impose a positive effect on the worker's "Intention to Behave Safely" indirectly via a mediating factor of "Chance Locus". The study conveys practical implications to safety management and researchers. Research limitations and areas for further study are also discussed. Safety behavioural initiatives based on the model testing results in promotion workers' safety behaviours are also addressed.

Heart Failure is a common long term progressive and serious medical condition with high mortality and costly health services in the UK. By the year of 2010, there were around 90,000 people in the UK suffered from heart failure and in 2008, 10,000 heart failure patients were recorded death. Treatments of heart failure cost the National Health Service around £625 million every year. Although heart failure is highly pro-arrhythmic, the underlying mechanisms of the pro-arrhythmic effects of heart failure are not completely understood. Heart failure is associated with electrical remodelling of the properties and kinetics of some ionic channels responsible for the action potential of cardiac cells. However, it is still unclear whether this ionic channel remodelling can account for the pro-arrhythmic effects of heart failure as the complexity of the heart impedes a detailed experimental analysis. Biophysically detailed computational models have been developed in the last two decades, enabling the evaluation of experimental data. The aim of this thesis is to use arrhythmic mechanisms to investigate the pro-arrhythmic effects of heart failure-induced remodelling on the cardiac action potentials and Purkinje-ventricular junction. Single canine Purkinje fibre and ventricular cell models were developed to investigate the effects of heart failure-remodelled ionic channel currents on cell action potentials and identify optimal options for the potential clinical treatments. One-dimensional strand tissue model and three-dimensional wedge model were developed to further explore the effects of heart failure-induced remodelling in propagation of the canine Purkinje fibre, ventricle and Purkinje-ventricular junction. It was found that heart failure-induced remodelling on the Purkinje fibre and ventricle reduced the conduction safety and increased tissue’s vulnerability to the genesis of the unidirectional conduction block, especially at the Purkinje-ventricular junction, which may cause conduction failure, re-entry or both.

Edifici industriali e magazzini con grandi quantità di materiali stoccati dovrebbero essere generalmente protetti da un sistema di soppressione antincendio attiva. Nonostante ciò, esistono molti edifici che non possiedono questi sistemi di sicurezza. La disciplina della Fire Safety Engineering (FSE) affronta, con metodi ingegneristici, il problema della scelta delle misure di sicurezza adeguate da adottare negli edifici al fine di garantire la protezione delle persone, dei beni e dell’ambiente dagli effetti dell’incendio. Attraverso l’approccio prestazionale della FSE si definisce lo scopo del progetto di protezione antincendio che si vuole adottare e gli obiettivi da conseguire; gli effetti dell’incendio sono quantificati e il livello di sicurezza antincendio viene valutato rispetto a soglie prestazionali prestabilite, relativamente alla temperatura, alla visibilità ed all’altezza dello strato libero da fumo. Il presente lavoro di testi è stato sviluppato presso la società IDF Studio – Ingegneria Del Fuoco s.r.l., situata a Funo di Argelato (BO) una società che si occupa della valutazione e della riduzione del rischio di incendio. Lo scopo del presente lavoro è di confrontare due codici di calcolo al fine di verificare l’efficacia dei sistemi antincendio secondo i principi della FSE: il software FDS (Fire Dynamic Simulator) e il software OpenFOAM (Open source Field Operation And Manipulation). Questi codici di calcolo sono stati applicati ad un magazzino automatizzato reale, al fine di simulare il più gravoso degli incendi che potrebbe svilupparsi al suo interno. Tale magazzino è definito, ai sensi del D.M. 10/03/98, un luogo di lavoro a rischio di incendio elevato.

Deterministic computer fire models have progressed over recent years to the point of providing good predictions for some parameters of fire behaviour. However, input data are not always available, and many factors that affect the course of a fire are probabilistic in nature and cannot be determined from physics. One way of surmounting the problem of unavailability of the values of the input parameters is to take them as random variables. By specifying an unsafe region in the output space and calculating its probability, we can obtain a figure for the reliability of the design being tested, in terms of the probability of the unsafe region. In practice, evaluation of the probability distribution of the output space cannot in general be carried out analytically because of the complexity of the computer fire models. An alternative method is to use Monte-Carlo simulation. But it usually requires a large amount of calculation to reach sufficient accuracy, particularly if the probability of the unsafe region is small, as it should be if the design is to be reasonably reliable. Also, if the probability distribution of the input is changed, the whole Monte-Carlo simulation must be redone ab initio. An approach that has been recently advocated in the structural reliability context is that of the response surface method. It consists in representing each output parameter by a nonlinear function of the input parameters. Usually, a quadratic function of the input parameters turns out to be sufficient. Fitting of the response surface is carried out by regression. However, if the range of the input parameters is comparatively large, it is unlikely that one quadratic function will fit the whole range. It then becomes necessary to break up the full range of input parameters into smaller subranges and fit a quadratic function separately to each subrange.

The building regulations in Australia and other countries are being reformed from a prescriptive basis of designing fire safety system requirements to a performance basis, which requires the application of engineering principles. Under the prescriptive regulations, fire resistant construction elements were tested using a standard fire resistance test heating regime, which is invariably quite different from the characteristics of real fires. The engineered approach requires the ability to predict the performance of elements of construction that may have different details those tested under the standard heating regime and under different heating regimes. This thesis comprises part of a comprehensive research program undertaken at the Centre for Environmental Safety and Risk Engineering, Victoria University of Technology to develop a comprehensive framework to determine the time dependent probability of failure of timber-framed assemblies subjected to real fires. The objective of the thesis is to determine the structural response of plasterboard-clad, timber framed walls subject to fire and is a key component that is incorporated into the framework to determine the probability of failure of timber-framed assemblies subjected to fire. The structural model simulates dominant phenomena, which have conventionally been ignored in the determination of the structural response of timber-framed walls in fire. The phenomena considered include the degradation in mechanical properties of materials due to thermal effects, non-linear mechanical and geometric effects caused through buckling, partial composite interaction with the plasterboard sheeting, thermal expansion and shrinkage and varied end restraint conditions. These phenomena have been modelled using common frame analysis methods to provide a computationally efficient and robust model. A transient, second-order direct stiffness approach has been utilised, with specific elements devised to consider the partial composite interaction. In conjunction with the development of the model, a comprehensive experimental program has been undertaken, to provide a means of comparison of the model predictions, and to obtain data found to be lacking in the literature. A series of full-scale experiments were conducted on timber framed assemblies under ambient and elevated temperature conditions. The variability, end restraint conditions and contribution of the sheeting were carefully controlled and examined in the experiments. The literature review identified that there was a lack of data detailing the reduction in the modulus of elasticity in compression with temperature. This was considered the most critical mechanical property in determining the time-to-failure of a load bearing timber-framed wall and so a series of experiments was undertaken on short lengths of timber to determine the reduction in the mechanical properties in compression with temperature. The full-scale experiments demonstrated the significance of end restraint and the influence of plasterboard sheeting on the time-to-failure. The full-scale experiments also showed an apparent rapid drop in the apparent stiffness of the timber framing as it approached a mean temperature of approximately 1 OODC through the cross-section. The reduction in the mechanical properties of radiata pine in compression due to elevated temperature exposure was determined directly from tests. It was determined that there was a significant reduction in the mechanical properties in compression of moist timber specimens heated to 70DC, compared with dry specimens. This finding was consistent with results from the full-scale experiments. The structural response model was successfully validated against closed form and finite element solutions and the predictions of the model compared closely with results from a series of full-scale experiments undertaken as part of the research. The deformation induced in the full-scale experiments was irrecoverable and may have been associated with a mechano-sorptive type creep phenomenon, although further research is required to study this phenomenon. This is one several areas requiring future research that has been identified by the author.

Deterministic computer fire models have progressed over recent years to the point of providing good predictions for some parameters of fire behaviour. However, input data are not always available, and many factors that affect the course of a fire are probabilistic in nature and cannot be determined from physics. One way of surmounting the problem of unavailability of the values of the input parameters is to take them as random variables. By specifying an unsafe region in the output space and calculating its probability, we can obtain a figure for the reliability of the design being tested, in terms of the probability of the unsafe region. In practice, evaluation of the probability distribution of the output space cannot in general be carried out analytically because of the complexity of the computer fire models. An alternative method is to use Monte-Carlo simulation. But it usually requires a large amount of calculation to reach sufficient accuracy, particularly if the probability of the unsafe region is small, as it should be if the design is to be reasonably reliable. Also, if the probability distribution of the input is changed, the whole Monte-Carlo simulation must be redone ab initio. An approach that has been recently advocated in the structural reliability context is that of the response surface method. It consists in representing each output parameter by a nonlinear function of the input parameters. Usually, a quadratic function of the input parameters turns out to be sufficient. Fitting of the response surface is carried out by regression. However, if the range of the input parameters is comparatively large, it is unlikely that one quadratic function will fit the whole range. It then becomes necessary to break up the full range of input parameters into smaller subranges and fit a quadratic function separately to each subrange.

The motivation for undertaking this research is to contribute to the development of a model of fire spread over a surface, and to integrate this model with a computational fluid dynamics (CFD) model that is capable of making predictions of the environment associated with full-scale fires in enclosures. The research focuses on the growth and spread stage of such fires, where a small, localised flame spreads across a single fuel item, increasing the heat release rate. In particular, the phenomenon of opposed flow flame spread across flat, non-charring, thermally thick fuel surfaces is examined.

This research investigates the spread of fire and smoke in buildings as well as occupant egress. There are existing deterministic models for these. While deterministic models provide averages of a process, stochastic models give the broad spectrum of all possible scenarios of the process giving the distribution function. The spread of smoke was first modelled by adding a noise component to the equation of an existing deterministic model. Later a deterministic model was developed and stochastic expressions derived using the Markov chain methodology. Though the Markov chain is a discrete process, it was used in approximating smoke spread which is a continuous process. The spread of fire was investigated using network analysis. Various methods of modelling the spread of a phenomenon in a network were compared.

Fire events in high-rise residential buildings pose threats to both property and human life and upon investigation it is frequently revealed that the cause of a fire event is not simply due to technical errors. Often these investigations uncover human and organizational errors (HOEs) that contribute to fire risk and fire events. Many human factors identified in fire risk environments can be minimized through employee training and development while organizational factors, such as safety culture, can be changed over time through transformational interventions that shift existing mindsets. Probabilistic risk analysis (PRA) methods are modeling tools that allow fire risk professionals to estimate risk by computing several scenarios of what can go wrong, the likelihood of events occurring, and the consequences of the events. PRA often takes a fixed value of events occurring likelihood over the building design period, whereas it may change due to aging of a fire safety measure. PRA is an explicit methodology for complying with performance requirements of building codes, but existing PRA methods may underestimate safety risk levels by ignoring HOEs while focusing solely on technical risks and errors as well as not taking into account reliability changes over the time. In this work, a systematic review identifies HOEs that can potentially affect risk estimates in fire safety modelling of high-rise buildings. The importance and uniqueness of high-rise buildings is mainly due to the special nature of buildings where fire-fighting techniques require different safety measures than in other industries. In addition, the height of high-rise buildings and the increased number of occupants result in longer evacuation times than other types of buildings or industrial plants. Evacuation times are increased further when the number of stairways in these buildings is limited. A wide range of HOEs have been identified as impacting risk in various industries such as offshore oil production and nuclear plants, but not all these identified HOEs will be appropriate for high-rise buildings. Important factors are those that emerge consistently from different published sources supported by quantitative case studies of events such as the Grenfell Tower fire in London and the fire in the Lacrosse building fire in Melbourne. The linking of published HOEs with errors identified from high-rise building fire case studies uncover HOEs likely to influence risk estimates. Quantifications of the impact of HOEs on risk estimates in other industries indeed justify additional research and inclusion of HOEs for risk estimates in high-rise buildings. This work uniquely connects HOEs from various industries to likely HOEs associated with risks in high-rise buildings to address an important gap in the literature. The research provides empirical quantitative studies, theoretical framework, and guidelines demonstrating how HOEs risks can be distilled to improve PRAs of fires in high-rise buildings. To further address the gap, this work proposes a comprehensive Technical- Human-Organizational Risk (T-H-O-Risk) methodology to enhance existing PRA approaches by quantifying human and organizational risks. The methodology incorporates Bayesian Network (BN) analysis of HOEs and System Dynamics (SD) modeling for dynamic characterization of risk variations over time in high- rise residential buildings. Most current approaches assume that the relationships among HOEs are independent and current methods do not explain the interactions among these variables. An integrated T-H-O-Risk model overcomes this limitation by measuring causal relationships among variables and quantifying HOEs such as staff training, fire drill practices, safety culture and building maintenance. The model addresses the underestimation of risk resulting from not following the proper practices and regulations. Issues of selecting fire safety measures needed to reduce risk to an acceptable level are examined while evaluating the efficacy of active systems that are sensitive to HOEs. The methodology utilizes the “as low as reasonably practicable” (ALARP) principle in comparing risk acceptance for different case studies demonstrating the model’s value related to risk reduction with respect to initial designs of high-rise residential buildings. By incorporating both BN and SD techniques, the T-H-O-Risk model developed in this research evaluates HOEs dynamically in an innovative and integrated quantitative risk framework. This is possible by incorporating factors that vary with time since event tree/fault tree (ET/FT) and BN alone cannot deal with dynamic characteristics of the process variables and HOEs. The model includes risk variation over time which is significantly better than contemporary methods that only provide static values of risks. Initially three case studies are conducted with limited number of scenarios for the purpose of validation to demonstrate the application of this comprehensive approach to the designs of various high-rise residential buildings ranging from 18 to 24 stories. Societal risks are represented in F-N curves. Results show that in general, fire safety designs that do not consider HOEs underestimate the overall risks significantly which can reach 40% in some extreme cases. Furthermore, risks over time due to HOEs vary by as much as 30% over 10 years. A sensitivity analysis indicates that deficient training, poor safety culture and ineffective emergency plans have significant impact on overall risk. Subsequently, the application of the T-H-O-Risk methodology was expanded to seven designs of high-rise residential buildings (including earlier three) with 16 different technical solutions to quantify the impact of HOEs on different fire safety systems. The active systems considered are sprinklers, building occupant warning systems, smoke detectors, and smoke control systems. The results indicate that HOEs impact risks in active systems by approximately 20%, however, HOEs have a limited impact on passive fire protection systems. Large variations are observed in the reliability of active systems due to HOEs over time. Finally, sensitivity and uncertainty analyses of HOEs were carried out on three selected buildings from the above seven. The sensitivity analysis again indicates that deficient training, poor safety culture and ineffective emergency plans have significant impact on overall risk. The model also identifies multiple cases where tenable conditions are breached. A detailed uncertainty analysis is carried out using a Monte Carlo approach to isolate critical parameters affecting the risk levels. This research has developed a novel approach to enhance fire risk assessment methods using a holistic quantification of technical, human, and organizational risks for high-rise residential buildings which ultimately benefits future risk assessments providing more precise estimates. A significant contribution of this research involves the systematic identification of HOEs and their associated risks for consideration in future PRAs. By studying various trial designs, the impact of HOEs on fire safety systems is analyzed while demonstrating the robustness of the T-H-O-Risk methodology for high-rise buildings. The research lays foundations for next-generation building codes and risk assessment methods.