Dissertations / Theses on the topic 'Experimental fires'
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Marsden, James Anthony. "Experimental and numerical studies of whirling fires." Thesis, University of Central Lancashire, 2005. http://clok.uclan.ac.uk/8689/.
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Motivation of this study stems from the need to understand the physical mechanisms of whirling fires that occur in an open space and within enclosures. Buoyant whirling flames may be potentially more destructive than ordinary fires due to greater burning rate, higher concentration of heat release in a small region of the plume core, increased radiative output and unexpected smoke movement. The effects of rotation upon the structure and behaviour of buoyant flames have not yet been thoroughly studied and understood. Investigation of this phenomenon is therefore required to allow techniques to be developed that will counter the threat of such outbreaks. Also, the mechanisms controlling the development and stability of whirling flames are of fundamental interest for refined modelling of coherent and self-organised flame behaviour. This work, is an experimental, theoretical and numerical study of whirling fires. Experimental results, a modified CFD model and simulations of whirling flames are presented within this Thesis. The work aims to overcome the limitations of the previous research of whirling fires which is insufficient from both an experimental and theoretical point of view. Firstly, experimental studies of intermediate (room-size) scale whirling fires have not yet been comprehensively reported, despite a great deal of attention devoted to both large scale mass fires and smaller laboratory flames. Experimental studies undertaken using a facility at the Greater Manchester Fire and Rescue Service Training Centre fill this gap, thus demonstrating that whirling flames may develop within a compartment. The periodic precession, formation and destruction of the whirling flame and the increase of the time-averaged burning rate (compared to non-whirling flames in the open space) have been observed. Three fuels with significantly different burning rates (diesel, heptane and ethanol) were investigated in this work. Secondly, previously published results of theoretical analysis of rotating flames were oversimplified and based on strict limitations of the integral model or the inviscid flow assumption. Also there have only been few attempts to undertake CFD modelling of whirling flames. In published studies, radiative heat transfer was not modelled and the burning rate was not coupled with the incident heat flux at the fuel surface. To overcome these limitations, the CFD fire model Fire3D, developed in the Centre for Research in Fire and Explosion Studies, has been adapted to allow numerical simulations of rotating buoyant turbulent diffusion flames. The turbulence model was modified to take into account stabilisation of turbulent fluctuations due to the centrifugal acceleration within the rotating flow. Theoretical analysis of the vorticity equation revealed the physical mechanisms responsible for vorticity concentration and amplification in the rising plume affected by externally imposed circulation. This explains the significant flame elongation (when compared to non-rotating cases) observed in the experiments. Computational results have also been compared to video-recordings of the experimental flames produced; flame elongation was replicated and similar stages of oscillating flame evolution, including formation and destruction of the vortex core, have been identified. Implications of the phenomena studied in relation to fire engineering are also provided. This study contributes to a performance based framework for an engineering approach, which is reliant upon detailed quantitative analysis and modelling. Such an approach is encouraged by modem fire safety legislation including the guides to fire safety engineering BS9999-21 and BS79742 'British Standard 9999-2 Draft Code of Practice for fire safety in the design, construction and use of buildings. BSI, 2004. UK. 2 British Standard BS7974 Application of fire safety engineering principles to the design of buildings. BSI, 2001-2003. UK.
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Peatross, Michelle J. "An experimental study of forced ventilation glovebox fires." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09122009-040230/.
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Utiskul, Yunyong. "Theoretical and experimental study on fully-developed compartment fires." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/4158.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Skelly, Michael J. "An experimental investigation of glass breakage in compartment fires." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42192.
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An experimental investigation has been completed which studied the breaking of window glass by fire. The experiments were carried out in a specially designed compartment to achieve two-layer flows characteristic of normal building fires. The experimental data was collected from two test groups: the first for windows with their edges insulated from the fire (edge-protected) and the second for windows uniformly heated by the fire (edge-unprotected).
The results of the edge-protected window tests indicated that the glass breakage was caused by a critical temperature difference between the central heated portion of the pane and the glass edge. The experimental work showed the critical value to be approximately 90C. After the material properties of the glass were determined, the theoretical findings of Keski-Rahkonen were used to obtain a value of 70C; the difference attributed to radiative heating. The test results also demonstrated a distinctive loss of integrity by the windows. When breakage occurred, the cracks spread throughout the glass, joined together and caused at least partial collapse of the pane.
The results from the edge-unprotected window tests were quite different. There were relatively few cracks developed and almost no propagation across the glass. Consequently, there was no window collapse in any of these cases. The breakage did initiate at a consistent glass temperature value, however, the mechanism for these tests is not known.Master of Science
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Beji, Tarek. "Theoretical and Experimental Investigation on Soot and Radiation in Fires." Thesis, University of Ulster, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.516439.
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Lata, Mary Elizabeth. "Variables affecting first order fire effects, characteristics, and behavior in experimental and prescribed fires in mixed and tallgrass prairie." Diss., University of Iowa, 2006. http://ir.uiowa.edu/etd/72.
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Flood, Maura Fiona. "An experimental investigation of the performance of glazing systems exposed to enclosure fires." Thesis, University of Ulster, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288822.
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Perelli, Matteo. "Pool fires in open atmosphere and in air-tight compartments: experimental measurements and mathematical predictions of the heat release rate." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
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The energy consumption in Europe is for the 40% accountable to households and the building sector. In the European Directive 2010/31/EU the main topic is the construction of highly efficient dwellings exploiting renewable sources of energy and engineered methodologies to heat up and insulate their premises. Passive houses are one example of these highly efficient constructions. Inside these new hazards can be outlined when a fire is triggered. The main parameter that has to be focused is pressure, which is the most important value when an occupant has to open a door to escape from a fire. The maximum force that a person can exert to open a door is 133 N. In the literature high values of overpressure have been reported, which means that this value of force is undoubtedly overcome, preventing the inhabitant to open the door to escape. Simulations with the use of the software FDS (Fire Dynamics Simulator) were carried out to show whether it is able to predict the heat release rate of a heptane pool fire. Firstly, heptane pool fires were simulated outdoor. Then, comparisons were drawn with experimental tests to explain the positive aspects and the drawbacks faced in the study. Secondly, the heptane pool fires were put inside a building, representing the passive house. The first step about the prediction of the heat release rate did not give consistent outcomes, involving a high heat flux on the pool surface, resulting in an important overestimation of the heat release rate. Instead, fixing the heat release for fires inside the enclosure shows good agreement, however mistakes in the temperature field of the gas phase showed up. In conclusion, the software FDS can be considered a reliable software to predict the heat release rate for heptane pool fires in open atmosphere. Nonetheless, inside a building, important drawbacks have been displayed which are not present, at least not at a such high level, for a fire in which the heat release rate results fixed as an input data.
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Mishra, Kirti Bhushan [Verfasser], Christof [Gutachter] Schulz, and Axel [Gutachter] Schönbucher. "Experimental investigation and CFD simulation of organic peroxide pool fires (TBPB and TBPEH) / Kirti Bhushan Mishra ; Gutachter: Christof Schulz, Axel Schönbucher." Berlin : Bundesanstalt für Materialforschung und -prüfung (BAM), 2015. http://d-nb.info/1121035728/34.
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Dong, T. T. Trang. "Chemical composition and toxicity of emissions from burning five vegetation types of Western Australia under experimental combustion conditions." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2019. https://ro.ecu.edu.au/theses/2180.
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This study investigated the emission factors (EFs) for inorganic gases (CO2, CO, SO2, NO and NO2), carbonyls (formaldehyde, acetaldehyde, acetone, propionaldehyde, butyraldehyde and benzaldehyde), volatile organic compounds (VOCs) and particulate matter (PM2.5 and PM10) from laboratory-based fires of vegetation from five typical vegetation types of Western Australia. Species burnt were three grasslands (Spinifex represented by Triodia basedowii, Kimberley grass represented by Sehima nervosum and Heteropogon contortus, and an invasive grass represented by Ehrharta calycina (Veldt grass)), Banksia woodland and Jarrah forest under different combustion conditions. Chemical composition (water-soluble metals and polycyclic aromatic hydrocarbons – PAHs) and in vitro toxicity of PM2.5 were also measured. Vegetation samples were burnt in a ceramic chamber in varying combustion conditions altered by controlling the vegetation moisture content (<10%, 12–16% and 20–25%) and the air flow rate (0, 1.25 and 2.94 m.s-1). Burns of woodland (Banksia) and forest (Jarrah) had significantly higher EFs for CO, SO2 and PM2.5 compared with those from grassland (Spinifex). Emissions of temperate grass (Veldt) fires were significantly different from those of the tropical grass (Spinifex and Kimberley grasses), with lower EFCO2 and higher EFs for CO, carbonyls and PM2.5. EFs for SO2, NO and NO2 were variable between different vegetation types, indicating variation in the nitrogen and sulphur content of the fuels. The EFs for most carbonyls were similar between most vegetation types, with the exception of Veldt grass. Functions which may be useful to predict emissions of infrequently measured carbonyls (acetaldehyde, acetone and propionaldehyde) from the EF for formaldehyde, a commonly measured and reported substance, were also proposed. Fifteen VOCs were identified in the smoke, but concentrations were too low to be quantified. Benzene, toluene, styrene and indene were the most frequently detected VOCs.
Moisture content did not strongly influence the modified combustion efficiency (MCE) and EFs for gaseous pollutants, but significantly affected the EF for PM2.5 with higher emissions from burns of moister vegetation. Increasing the air flow rate significantly increased the emissions of most pollutants. However, combustion conditions did not strongly affect the PM2.5 chemical composition.
The MCE, EFs for CO and CO2 results in this study were similar to values reported from field measurements for similar vegetation types in Australia, indicating the applicability of these laboratory-based results. Emission factors were different to the profiles generated from vegetation fires in other parts of the world.
Toxicity of PM2.5 on human lung epithelial (A549) cells was assessed using cell viability and cytokine production measurements. Responses on cell viability were associated with K and Na concentrations in PM2.5, whilst the cytokine production of cells was more affected by the PM2.5-bound PAH, Al, Cu and Mn concentrations. Toxicity between vegetation types was different, which might be due to the differences in chemical composition of PM2.5. PM2.5 emitted from Jarrah burns appeared to have the highest toxicity on epithelial cells, followed by those from Banksia, Veldt grass and Spinifex. The findings of this study on toxicity of PM2.5 demonstrate the adverse impact on human health of particulate from bushfires and emphasise the importance of vegetation type on toxicological outcomes of bushfire-derived PM2.5.
The EFs obtained in this study can be used in models to estimate the emissions from bushfires in Australia, particularly Western Australia. Results on toxicity of PM2.5 provide information for relevant government agencies to preliminarily evaluate the risk to human health, especially for firefighters and communities in close proximity to bushfire events.
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Fayad, Jacky. "Études numériques des feux extrêmes." Electronic Thesis or Diss., Corte, 2023. http://www.theses.fr/2023CORT0015.
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Les feux extrêmes sont des feux caractérisés par une forte puissance et une vitesse de propagation élevée qui rendent les moyens de lutte impuissants. Ces phénomènes entraînent une augmentation des dégâts et du nombre de décès civils et opérationnels, et perturbent les écosystèmes ainsi que nos sociétés. Il existe plusieurs types de feux extrêmes, dont les feux de forte puissance qui sont l’objet de cette thèse. Ce type de feux constitue un réel risque, étant donné l’augmentation de sa fréquence et son impact dans le monde entier. Par conséquent, l’évaluation des conditions de propagation qui peuvent déclencher un feu de forte puissance, s’avère très utile dans le but d’anticiper ces phénomènes. De plus, l’étude du comportement d’un feu de forte puissance (vitesse de propagation, intensité et impact) est susceptible de fournir des renseignements aux opérationnels en phase de lutte. L’objectif principal de cette thèse est d’étudier la propagation des feux de forte puissance à l’aide des feux expérimentaux réalisés à l’échelle du terrain sur du maquis Corse « Genista salzmannii ». Ces expériences ont été menées lors des deux saisons (hiver et automne), dans deux régions différentes de l’Île (Nord-Ouest et Sud-Ouest de la Corse), selon un protocole expérimental et des techniques qui permettent d’évaluer la dynamique et l’impact de ces feux. À la suite des expériences, des études numériques ont été menées à l’aide des codes physiques complets FireStar2D et 3D, basés sur une approche multiphasique, afin de tester la pertinence de ces modèles de propagation dans la prédiction du comportement des feux expérimentaux de forte puissance. Les différents résultats numériques obtenus pour les trois configurations choisies, ont montré une bonne adéquation avec les résultats expérimentaux. Ceci montre que ces modèles peuvent être utilisés pour étudier d’autres configurations sans avoir forcément recours aux expériences. Les campagnes de feux réalisées étaient représentatives des feux de forte puissance, qui ont eu lieu malgré des conditions marginales de propagation dues à des vitesses de vent faibles, des teneurs en eau du combustible ainsi que des humidités relatives de l’air élevées. Ces expériences pourront également fournir des observations détaillées, utiles pour améliorer la modélisation. Ceci représente une avancée significative, étant donné la complexité et les difficultés de la mise en œuvre des expériences sur le terrain. La deuxième partie de la thèse a porté sur une étude numérique d’un « cas critique » d’un feu de forte puissance. Ce feu a été étudié suivant plusieurs approches : empiriques, physiques complètes et simplifiées. En particulier, FireStar2D et 3D et le modèle physique simplifié de Balbi ont été mis en œuvre. Plusieurs paramètres ont ainsi été évalués par les différentes approches, dont la vitesse de propagation, l’intensité du front de flammes, la géométrie du front et de la flamme (longueur et inclinaison). L’objet principal de cette étude, était non seulement d’évaluer le comportement mais surtout l’impact de ce feu de forte puissance sur deux cibles : un corps humain et un bâtiment de quatre étages. Cela a permis d’établir des corrélations qui lient les flux de chaleur totaux reçus par les cibles en fonction de leur position du front de feu. L’objectif était d’évaluer la distance de sécurité autour des interfaces forêt-habitat, en considérant la valeur maximale tolérable du flux de chaleur thermique, qui peut être reçu par la cible sans causer de dommages. . Les distances de sécurité évaluées à l'aide de cette méthodologie, pour un pompier et un bâtiment, sont inférieures à 50 mètres. Ceci confirme, pour cette configuration, l'efficacité de la valeur de la distance de sécurité autour des habitations, fixée par les experts opérationnels et supposée égale à un minimum de 50 m en FranceExtreme fires are characterized by their high intensity and rate of spread, which overwhelm firefighting resources. These phenomena result in increased damage, civilian and operational fatalities and disruption to ecosystems, human life and the economy. There are several types of extreme fires, including high-intensity fires, which are the main subject of this thesis. This type of fire presents a real risk, given the increase in its frequency and scale throughout the world. Consequently, it is very useful to assess the conditions of propagation that can trigger a high- intensity fire in order to be able to anticipate these phenomena. In addition, studying the behavior of a high-intensity fire (rate of spread, intensity and impact) can provide information to operational staff during the firefighting phase. The main aim of this thesis is to study the propagation of high-intensity fires by means of experimental fires carried out on a field scale on Corsican shrub species named 'Genista salzmannii'. These experiments were carried out during two periods (winter and autumn), in two different regions: North-West and South-West of Corsica, using an experimental protocol and technologies that make it possible to assess the dynamic and impact of these fires. Following the experiments, numerical studies were carried out using fully physical fire models based on a multiphase formulation, FireStar2D and 3D, in order to test the relevance of these propagation models in predicting the behavior of these experimental fires. The different numerical results obtained for the three terrain configurations chosen were in agreement with the experimental results. This shows that these models can be used to study other configurations without necessarily having to resort to experiments. The fire campaigns carried out were representative of high-intensity fires that occurred despite marginal propagation conditions related to low wind speeds, high fuel moisture content and relative air humidity. These experiments can also provide detailed observations, as well as input data that can be used in modelling, given that carrying out such experiments is not easy and is always subject to difficulties and constraints. The second part of the research focused on a numerical study of a "critical case" of a high- intensity fire. This fire was studied using several empirical approaches, fully physical models found in the literature, in particular FireStar2D and 3D and the simplified physical Balbi model. Several parameters were evaluated using the different approaches, including the rate of spread, the intensity of the flame front, the geometry of the front and of the flame (length and tilting). The main aim of this study was to assess not only the behavior but also the impact of this high-intensity fire on two different targets: the human body and a four level building. This made it possible to establish correlations between the total heat fluxes received by the targets as a function of their position in front of the fire. The aim was to assess the safety distance around wildland urban interfaces by considering the maximum tolerable value of thermal heat flux that can be received by the target without causing damage. The safety distances assessed using this methodology, for a firefighter and a building, are less than 50 meters. This confirms, for this configuration, the effectiveness of the value of the safety distance around buildings, set by operational experts and assumed to be equal to a minimum of 50 m in France
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FILHO, ROMILDO DIAS TOLEDO. "COMPOSITE MATERIALS REINFORCED WITH NATURAL FIBRES: EXPERIMENTAL CHARACTERIZATION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2144@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORBRITISH COUNCIL
UNIVERSIDADE FEDERAL DA PARAÍBA
A presente tese estuda as propriedades de curta e londa duração de argamassas de cimento reforçadas com fibras de coco e sisal. O trabalho experimental visou a determinação das propriedades físicas e mecânicas do reforço e o estudo da influência do tipo, fração volumétrica e tamanho de fibra, orientação e composição da matriz nas propriedades mecânicas do compósito. Estudos foram executados com o objetivo de se determinar a influência do reforço na retração plástica, com e sem restrições, das matrizes de argamassa. Fissurações resultantes da imposição das restrições e o fenômeno de cicatrização das fissuras foram também investigados. O modo de ruptura e as propriedades de aderência interfacial fibra-matriz foram determinados através de ensaios de arrancamento. As propriedades de longa duração dos compósitos foram determinadas através dos ensaios de fluência, retração e durabilidade. A influência da adição de várias frações volumétricas e tamanhos de fibras na fluência das matrizes de argamassa foi determinada usando-se corpos de prova, selados e não selados, submetidos a uma pressão de 14,4 MPa durante um período de 210-350 dias. Recuperações das deformações elásticas foram monitoradas por um período de 56-180 dias. A influência dos tipos de fibra, fração volumétrica, tamanho de fibra, tipo de cura, traço da argamassa e substituição parcial do cimento Portland por micro-sílica e escória de alto forno na estabilidade dimensional das matrizes de argamassa foi determinada com o uso de ensaios de retração por um período de 320 dias. A durabilidade das fibras de coco e sisal, imersas em soluções alcalinas de hidróxido de cálcio e de sódio e em água de torneira, foi determinada através da realização de ensaios de resistência à tração em idades variando de 30-420 dias. A durabilidade das argamassas reforçadas com fibras naturais após 320-360 dias imersas em água, expostas a ciclos de molhagem e secagem bem como ao ambiente natural foi determinada através de resultados de ensaios de flexão e de observações de imagens obtidas com o uso de microscopia eletrônica. Um mapeamento de elementos químicos foi realizado com o objetivo de se verificar possíveis migrações de produtos da matriz de cimento Portland para o lúmen e paredes das fibras. Tratamentos para garantir a durabilidade dos compósitos foram estudados, a saber: (a) modificações na matriz através da substituição parcial do cimento Portland por micro-sílica e escória de alto orno; (b) carbonatação da matriz de cimento Portland; (c) imersão das fibras em micro-sílica líquida antes de serem incorporadas à matriz de cimento Portand.
This thesis studies both the short-term and long- term behaviour of sisal and coconut fibre reinforced mortar composites.The experimental work involved extensive laboratory testing to determine the physical and mechanical properties of the fibre reinforcement and to study the influence of fibre type, volume fraction, fibre length, fibre arrangement and matrix composition on the mechanical properties of the composite.Studies were also made to determine the influence of fibre reinforcement in controlling free and restrained shrinkage during the early age of mortar mixes. Cracking due to restraint and the phenomenon of crack self-healing were also investigated. The mode of failure and the properties of the resistance to fibre-matrix interfacial bonding were determined using the single fibre pull-out test.The long-term properties of the sisal and coconut fibre reinforced-mortar composites were assessed throughout creep, shrinkage and durability tests. The influence of the addition of sisal and coconut fibres, of various volume fraction and lengths, on the creep of a mortar matrix was determined using sealed and unsealed specimens subjected to a pressure of 14.4 MPa over a period of 210-350 days. Recovery strains were recorded for a period of 56-180 days.The influence of fibre types, volume fraction, fibre lengths, cure types, mix proportions and replacement of OPC by slag and silica fume on the dimensional stability of mortar matrices was determined using drying shrinkage tests for a period of 320 days. The durability of sisal and coconut fibres exposed to alkaline solutions of calcium and sodium hydroxide and stored in tap water was measured as strength loss over a period of 420 days. The durability of fibre-reinforced mortars after 320 to 360 days, stored under water, exposed to cycles of wetting and drying as well as to the natural weather,was assessed from results of flexural tests and from observations of the photomicrographs obtained using backscattered imaging and secondary electron imaging. Dotting maps of chemical elements were obtained in order to verify possible migration of cement products from the matrix to the lumen and voids within of the fibres. Treatments to enhance the durability performance of the composites were studied,including: (a) modifications to the matrix through the replacement of Portland cement by undensified silica fume and by blast-furnace slag; (b) carbonation of the cementitious matrix and (c) immersion of the fibres in slurry silica fume prior to being incorporated into the Portland cement matrix.
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Lund, Anja. "Melt spun piezoelectric textile fibres : an experimental study." Doctoral thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3682.
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The manufacturing and characterisation of piezoelectric textile fibres are described in this thesis. A piezoelectric material is one that generates an electric voltage when deformed, a property which exists in a number of materials. The polymer with the strongest known piezoelectric effect today is poly(vinylidene fluoride) (PVDF), however it must be processed under certain conditions to become piezoelectric. This study shows that piezoelectric bicomponent PVDF-based fibres can be produced by melt spinning, which is a common and relatively simple fibre spinning method. The melt spinning process must include cold drawing, as this introduces a polar crystalline structure in the polymer. The fibres must also be electroded, which is done by producing bicomponent fibres with a core-and-sheath structure. The core is electrically conductive and constitutes an inner electrode consisting of a carbon black/polymer compound, whereas the sheath is PVDF and constitutes the piezoelectric component. Being sensitive to both deformation and temperature changes, these fibres are anticipated to be useful in a number of sensor applications. The flexibility and small size of the fibres makes it possible to include them as miniature-sensors in structures or garment without affecting the shape or comfort.
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Albrektsson, Joakim. "Durability of fire exposed concrete : Experimental Studies Focusing on Stiffness & Transport Properties." Licentiate thesis, KTH, Betongbyggnad, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-168386.
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Road and rail tunnels are important parts of the modern infrastructure. High strength concrete (HSC) is commonly used for tunnels and other civil engineering structures, since it allows high load carrying capacity and long service life. In general, Swedish road and rail tunnels should be designed for a service life of 120 years. However, HSC has shown to be sensitive to severe fires in the moist tunnel environment, i.e., fire spalling may occur. Extensive research shows that addition of polypropylene (PP) fibres in the fresh concrete mix significantly reduces the risk of fire spalling. The durability of a concrete structure is mainly governed by the transport properties. Further, experimental studies aimed at understanding the protective mechanism of PP fibres indicate that fluid transport increases in connection with the melting temperature of such fibres. This might reduce the durability of fire exposed concrete with addition of PP fibres. This study aims to investigate whether the use of PP fibres has any significant effect on the durability of moderate fire exposed concrete structures. The experimental study focused on transport properties related to durability and stiffness reduction of fire exposed civil engineering concrete with and without addition of PP fibres. The study consists of three parts; (i) unilateral fire exposure in accordance with the standard time-temperature curve (Std) and a slow heating curve (SH), (ii) uniformly heating of non-restrained samples to 250oC, and (iii) moderate unilateral fire exposure, 350oC, of restrained samples. Changes in material properties caused by the fire exposure were studied by means of ultrasonic pulse velocity, full field-strain measurements during uniaxial compression core tests, polarization and fluorescence microscopy (PFM), water absorption and non-steady state chloride migration. The study shows that fire exposure influences different properties of importance for load carrying capacity and durability. To get a clear image of the fire damage one has to combine different test methods during damage assessments. Transport properties of concrete both with and without addition of PP fibres were considerably affected even at moderate fire exposure. Hence, the service life might be reduced. All series with addition of PP fibres exhibited higher water absorption compared to the series without PP fibres. The practical importance of this might, however, be small since also the water absorption of concrete without PP fibres was considerably affected for the fire scenarios considered in this study. Behind the fire exposed surface, i.e., between 30 and 60 mm, no change in water absorption was observed for concrete without PP fibres. However, higher water absorption of the series with addition of PP fibres was observed. Indicative fire tests aimed to evaluate the resistance to fire spalling during a subsequent severe fire was also conducted. The concretes with addition of PP fibres showed no signs of fire spalling, while progressive spalling was observed for the concrete without PP fibres.QC 20150603
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Celik, Alper. "Experimental And Numerical Studies On Fire In Tunnels." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613857/index.pdf.
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Fire is a complex phenomenon including many parameters. The nature of fire makes it a very dangerous and hazardous. For many reasons the number of tunnels are increasing on earth and fire safety is one of the major problem related to tunnels. This makes important to predict and understand the behavior of fire, i.e., heat release rate, smoke movement, ventilation effect etc. The literature includes many experimental and numerical analyses for different conditions for tunnel fires. This study investigates pool fire of three different fuel sources: ethanol, gasoline and their mixture for different ventilation conditions, different geometries and different amounts. Combustion gases and the burning rates of the fuel sources are measured and analyzed. The numerical simulation of the cases is done with Fire Dynamics Simulator (FDS), a CFD code developed by NIST.
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Supporta, Giulio Fulvio. "Experimental study of jet fire impingment in pipelines." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
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The continuous growth of the global industrial sector has led to an increasing need for the transportation of oil, gas and chemicals through pipelines. The need for compactness of the pipelines along the corridors involves a relatively short distance between one pipe and another, thus leading to a certain degree of risk associated with their potential interaction. Furthermore, as the transported fluids may be flammable, any accidental release due to cracking or leakage in one of the pipelines could lead to an accidental scenario with severe consequences for the population, structures and the environment.
A hypothetical accident in one of these pipes can lead to the occurrence of a domino effect, leading to an escalation of effects involving the other pipes. In the case of jet fires, the thermal action produced may lead to a certain risk of ignition of the released material, thus causing a progressive increase in the severity of the consequences. With the development of a jet fire, the high thermal flow that reaches an adjacent pipeline can damage the secondary target by widening the scale of the accident, especially if there is flame impingement.
In order to study the thermal evolution of jet fires and quantify the thermal response of a target object placed perpendicular to the flame, a laboratory equipment has been used to obtain data on propane jet fires affecting a pipe containing a gaseous or liquid fluid.
In this experimental configuration, pressure and temperature measurements for various propane release rates were performed with the appropriate instrumentation in order to calculate the absorbed heat and convective heat exchange coefficient of the target tube.
In order to prevent the occurrence of these accidental fire scenarios, and in particular jet fire, a special type of passive fire protection, such as intumescent coatings, capable of forming an insulating layer when stressed by an external heat source, was also examined.
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Jansson, Robert. "Fire Spalling of Concrete : Theoretical and Experimental Studies." Doctoral thesis, KTH, Betongbyggnad, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-128378.
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Fire spalling of concrete is not a new phenomenon. To some degree there has always been a risk during rapid heating of concrete. Therefore, to a certain degree the effect of fire spalling is included in the bank of data from fire tests and fires on which our understanding of the fire resistance of concrete is based. However, the development and modern use of more dense concrete mixes have produced cases of very severe fire spalling which have increased the urgency to understand this phenomenon. In this context, the use of an addition of polypropylene (PP) fibres to the mix to limit the amount of spalling has been one topic of interest for this thesis. During fire tests on a post-tensioned concrete structure made of spalling sensitive concrete, it has been shown that substantially lower amounts of PP fibres than 2 kg/m3, which is recommended in the Eurocode (1992-1-2:2004), can be used with successful results. As part of this study, another important aspect has emerged, i.e. the impact the test method used can have on the fire spalling depths observed in concrete specimens. This has been known for many years but is seldom discussed in the scientific literature. In this thesis it has been shown that results from tests on unloaded cubes do not necessarily correspond to results seen on larger loaded slabs. In the results presented, none of the tested cubes spalled whereas some of the large slabs spalled to the degree that the reinforcement became fire exposed. Further, the difference in spalling depths between small and large post-tensioned slabs was shown to be substantial; although in general the ranking in severity from least to greatest spalling correlated between these two specimen sizes. The correlation to larger specimens was much vaguer in the case when the small slabs were not loaded in compression as there sometimes was no spalling in the small slabs. From time to time the randomness of the fire spalling of concrete has been mentioned. To investigate this further, an analysis of 110 fire tests performed on small slab type specimens was performed. This analyse showed that the spalling behaviour had a good repeatability between two identical tests, which proved that the so called “random factor” relating to spalling depth was low for the chosen data set. It was also possible to make a multiple least squares fit of test parameters that could be used to predict the spalling behaviour which also underlines that a substantial stochastic factor was not present. Regarding the influence of different factors, the results compiled on the influence of ageing show that for three of the tested Self-Compacting Concrete (SCC) mixes, the amount of spalling was reduced with age whereas for the fourth mix (which included the highest amount of limestone filler, 140 kg/m3) the spalling was not reduced with age. In this test series no systematic influence of the intensity of the fire, between standard fire exposure and the more severe hydrocarbon fire, on the spalling depth was detected for this type of specimen. The only major difference was that spalling started earlier during the more severe fire exposure. Pressure measurements conducted as part of the work within this thesis, supported by results from the literature, indicate that there is no relationship between pressure rise due to moisture and fire spalling. Based on this and the fact that the spalling event in many cases happens at relatively low temperatures where the saturation vapour pressure is low two alternative factors to explain the function of PP fibres have been presented: (i) PP fibres reduce the moisture content in the critical zone close to the heated surface which affects the mechanical properties advantageously, and (ii) PP fibres amplify moisture movement leading to larger drying creep and shrinkage which locally relax the thermal stresses. To investigate the influence of the presence of moisture on the compressive strength, specimens were tested after being boiled for varying periods of time in a water bath. The study showed a remarkable reduction of strength due to boiling of the mortar specimens. After boiling mortar in a water bath for 3, 10 or 20 minutes, i.e. approximately the same time span as the initiation of fire spalling during fully developed fires, the strength was only 64% of the corresponding value for a dry specimen. As no strength change was detected between the specimens boiled 3, 10 or 20 minutes, and that the corresponding saturation pressure for steam at 100ºC is negligible compared with the tensile strength of concrete, it was concluded that pore pressure is not a significant contributor to the measured reduction in strength. It appears that the presence of moisture itself rather than an increased pressure is the most important factor reducing strength. This is a clear indication that moisture plays a key role in the fire spalling of concrete but in a different way from previously assumed.QC 20130911
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Kucner, Lauren K. (Lauren Kathleen). "Experimental investigation of fire damage to composite materials." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11569.
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Nyazika, Tatenda. "Conceptualization of fire barriers : fundamentals and experimental approach." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R044/document.
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Le feu est à la cause des pertes en vies humaines et des dégâts matériels considérables. En cas d’incendie dans un système fermé tel que les bâtiments, navires, ou avions, un feu doit être compartimenté et sa propagation restreinte afin de sauver des vies et des biens en laissant le temps aux personnes d’évacuer. Afin d’y arriver, une barrière de feu ayant une très faible inflammabilité qui limiterait la propagation du feu doit être conçu et assemblé. L’objective de ce travail de thèse est de fournir les bases fondamentales pour la conception de barrières feu efficace quand ils subissent une contrainte thermique. En se basant sur la compréhension du comportement au feu de matériaux de références c.-à-d. le silicate de calcium, la mousse de mullite à cellules fermées, la mousse phénolique, et un revêtement intumescent à base de silicone, des tests feux avec un flux radiant externe basé sur la norme ISO 5660 du cône calorimètre sont effectués. En parallèle, des modèles numériques sont développés afin de prédire le comportement au feu de ces barrières feu. Leurs domaines d’application ainsi que leurs limites sont expliqués. Les propriétés physiques d’entrées requises pour alimenter les modèles sont obtenus soit par mesure directe par analyse thermique, soit de la littérature. Par ailleurs, des études de sensibilité sont effectués afin d’identifier les paramètres essentiels qui contrôlent le comportement au feu des matériaux de référence. Les modèles numériques sont ensuite appliqués à la conceptualisation de nouvelles barrières feu grâce à la méthodologie basée sur le "performance-based design" ainsi que l’optimisation. Enfin, après les étapes de conception et les études de sensibilité, les règles fondamentales sur la conceptualisation de barrières de feu pour un scenario feu précis en accord avec des normes définies sont énoncéesFire causes injuries, the loss of lives and property. In the case of a fire in an enclosed system such as buildings, naval ships or aircraft, the fire should be compartmentalized and restricted from spreading from one point to another in order to save lives and property as well as give people enough time to evacuate. To accomplish this, fire barriers exhibiting low flammability and limiting fire spread need to be designed and assembled. The aim of this PhD is to provide with the fundamentals on how to design efficient fire barriers when subjected to a thermal stress. Based on understanding the fire behavior of selected reference fire retardant materials i.e. calcium silicate, closed-cell mullite foam, phenolic foam and a silicone-based intumescent coating, fire tests using the external radiant heat flux from the ISO 5660 cone calorimeter are conducted. At the same time, numerical models are developed to predict the fire behavior of these fire barriers and their applicability as well as limitations are explained. The input materials properties to run the numerical models are obtained from both direct measurements and from the literature. In addition, sensitivity studies are conducted in order to identify the governing parameters that control the fire behavior of the reference fire resistant materials. The numerical models are then used for the conceptualization of innovative fire safe materials based on the performance-based design process and optimization. Finally, based on the sensitivity studies and the conceptualization process, fundamental rules on how to make an efficient fire barrier in order to meet certain requirements in a given fire scenario are clearly stated
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Chegenizadeh, Amin. "Experimental approach to investigate reinforced clay." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/2288.
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Soil reinforcement with discrete flexible fibres has always been an issue for further research. In Geotechnical engineering field, the research on sandy soil has considerably been more than the clayey one. The main reason for this lack can be expressed as the complexity of clayey material due to their cohesion and interaction between clay and reinforcement.The present research aims to show possibility of discrete fibre usage in clay. For this purpose, selection of material has been conducted with special care to make the project outcome applicable to industry projects. The fibre which was used for this research prepared by BASF Company in Western Australia and currently is used in fibre reinforced concrete for infrastructure projects. Kaolin has been used as soil part and provided by Prestige Company.Experimental approach was applied to investigate the effect of different parameters on composite soil strength. These tests cover the variety range of soil mechanics tests from compaction tests to triaxial compression tests. The results from all the tests were presented in the thesis.A theoretical model was also developed for clayey material for the first time with the use of modified cam clay model to predict the behaviour of samples precisely. This model is based on the rule of mixture and considers the effect of soil and fibre separately. The model was validated with the results from CD triaxial test.
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Chen, Aiping. "Empirical and experimental studies of flashover in compartment fire." Thesis, University of Central Lancashire, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410489.
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Dress, Jason Michael. "Experimental Evaluation of JP-8-Based Fire Resistant Fuels." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/76912.
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The Army's Fire Resistant Fuel (FRF) program is currently being used to defend against the threat of vehicle fuel fires resulting from unconventional warfare encountered in the Middle East. Fire Resistant Fuels are based upon JP-8, which is now the primary fuel for the Army ground services. The goal of FRF development is to reduce susceptibility to ignition at standard storage conditions while still serving as a fuel for the Army's diesel vehicles.
Two preliminary tests were conducted to narrow down a field of candidates developed by Luna Innovations to a final set of five FRF. Dynamometer testing was used to determine peak power of the supplied Yanmar 2V750 engine. Fuel fire resistance characteristics were defined and compared using a rotating disk anti-misting characterization system. Fuels were characterized based upon spray characteristics including velocity and droplet diameter as well as through ignition testing. For these tests, FRF were compared to Diesel and Jet-A results.
Results from this testing has shown that two fuels, both JP-8 emulsions, met the basic criteria of a fire resistant fuel. Engine testing trends showed that both fuels surpassed the peak power output of Diesel. Rotary atomization ignition testing resulted in no ignition for both fuels.
As a supplementary study, cone calorimetry testing was performed to determine effective heats of combustion. Results from experimentation demonstrated that the energy content of the FRF is not of primary importance to engine performance or flame resistance. All data, analysis and trends are located in the appendices.Master of Science
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HERZHAFT, BENJAMIN. "Etude experimentale de la sedimentation de suspensions de fibres." Paris 6, 1997. http://www.theses.fr/1997PA066100.
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Nous presentons une etude experimentale de la sedimentation de fibres non-browniennes dans un fluide newtonien. La technique experimentale utilisee est une technique optique d'ajustement de l'indice de refraction du fluide avec celui des particules, ce qui nous permet de mesurer les positions et les orientations locales des particules. Nous en deduisons la vitesse moyenne de sedimentation, les fluctuations de vitesse et la distribution d'orientation de suspensions de fibres en fonction de la concentration et du rapport d'aspect. Deux regimes distincts de sedimentation sont mis en evidence. Pour des suspensions tres diluees, les fibres s'agregent en paquets et tendent a s'aligner avec l'axe de la gravite, tout en effectuant des retournements entre les deux positions verticales. Dans ce regime, la vitesse moyenne de sedimentation n'est pas freinee (comme c'est le cas pour les suspensions de spheres) et peut atteindre des valeurs superieures a la vitesse de stokes d'une fibre verticale isolee. Pour des suspensions plus concentrees (fraction volumique superieure a 2%), l'orientation des particules est toujours majoritairement parallele a la gravite, mais la vitesse moyenne de sedimentation est freinee. Des experiences avec deux rapports d'aspect differents montrent que la vitesse moyenne adimensionnee est une fonction de la concentration volumique.
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Sotom, Michel. "Etude experimentale de l'ouverture angulaire de fibres optiques multimodes." Toulouse, INSA, 1986. http://www.theses.fr/1986ISAT0042.
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Procede de caracterisation de l'ouverture et de la transmittance angulaires base sur l'injection d'un faisceau laser sous incidence bien determinee dans une fibre fixe par l'intermediaire d'un jeu de miroir tournants gere par un microordinateur. Sont caracterisees des fibres multimodes dont un des constituants au moins est un verre organique. Le procede permet d'itentifier les differents mecanismes responsables des pertes de puissance et le role de l'absorbance de la gaine. Application a l'etude des proprietes de transmission de fibres soumises a des contraintes thermiques.
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Klinck, Amanda. "An Experimental Investigation of the Fire Characteristics of the University of Waterloo Burn House Structure." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/774.
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This thesis reports on the procedure, results and analysis of four full scale fire tests that were performed at the University of Waterloo's Live Fire Research Facility. The purpose of these tests was to investigate the thermal characteristics of one room of the Burn House structure. Comparisons were made of Burn House experimental data to previous residential fire studies undertaken by researchers from the University of Waterloo. This analysis showed similarities in growth rate characteristics, illustrating that fire behaviour in the Burn House is typical of residential structure fire behaviour. The Burn House experimental data was also compared to predictions from a fire model, CFAST. Recommendations were made for future work in relation to further investigation of the fire characteristics of the Burn House.
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Kahrmann, Steffen. "Experimental analysis of fire-induced flows for the fire-safe design of double-skin facades." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25422.
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Today, ever changing and advancing techniques of construction are constantly pushing the envelope of structural possibilities in the built environment. Although not new, the concept of Double-Skin Façades (DSF) finds increasing implementation with the advent of sustainable construction, aiming to reduce energy consumption to condition buildings whilst improving indoor air quality. As is the case with the traditional concept of the compartment fire, methodologies and assumptions on which our general understanding of the fire problem is based, did fundamentally not change. Inherently bound to this, is the concept of compartmentalisation, prescribing measures to avoid horizontal and vertical fire spread in buildings. A DSF, most commonly featuring a ventilated cavity between curtain wall and the secondary glass façade at an offset, is prone to drastically alter fire and smoke behaviour once able to enter. Unlike curtain walls, the chimney-like aspect ratio of such façades is able to trap fire and combustion gases within the cavity, potentially compromising the integrity of the building perimeter above the fire. The current approach to this issue tends to focus on using non-combustible construction materials and the installation of sprinkler systems to avoid breakage of window panes in the first place. Another topic of interest is the weak connection between floor slab and curtain wall which can allow vertical fire spread to adjacent floors. Research has also been discussing the use of mullions to deflect the fire plume away from the façade. Even if useful in DSF’s, aesthetics and problems with functionality will most likely prevent mullions from being introduced into the DSF. However, very little relevant research actually investigated the fire-induced flow structure under these conditions so that properly informed design decisions can be made. The project at hand aims to understand hazards to the floors above and below the fire floor by experimentally investigating the governing processes by means of large-scale fire testing and small-scale salt-water modelling (SWM). The gathered data shall serve as a basis to discuss current spandrel and cavity design decisions. Results have been compared in terms of dimensionless numbers and demonstrate complex interactions between DSF cavity width and spandrel height, encouraging a discussion about the need of further research of this topic.
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Gómez, Mares Mercedes. "Estudio experimental y modelización matemática de dardos de fuego." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/6480.
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Kao, Yi-Huan. "Experimental Investigation of NexGen and Gas Burner for FAA Fire Test." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342545254.
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Byström, Alexandra. "Fire temperature development in enclosures : Some theoretical and experimental studies." Licentiate thesis, Luleå tekniska universitet, Byggkonstruktion och -produktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18078.
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This thesis is devoted to problems connected to heat transfer and fire dynamics in enclosures. The thesis consists of a main part which summarizes and discusses the theory of heat transfer, conservation of energy and fire dynamics. Based on these theories, some cases of different fire scenarios have been analyzed. In the end of this thesis, the reader will find Paper I-IV containing four articles on the subject.The main focus of this thesis is fire temperature development in enclosures. For that reason, firstly, some experimental studies have been done using different thermo devices for measuring temperature. Based on the experience from these studies, temperatures measured with a Plate Thermometer have been used to predict and describe in a quantitative way the thermal exposure of structures. For more accurate prediction of this thermal exposure, PT and thin thermocouples measurements have been combined.This thesis summarizes the experimental data from two different setups. One was conducted in a large enclosure 20 m by 20 m and 20 m high. This experiment scenario can be characterized as localized fire. Another experiment was conducted in a compartment in full scale with a limited fire source, without reaching flashover. This second experiment did not reach flashover and can be categorized as a two-zone compartment fire. Moreover, the thesis contains a new way of analyzing a one-zone fire model intended for the analysis of fully developed ventilation controlled compartment fires.Temperature data from the localized fire experiment were collected with different designs of Plate Thermometers (PT), small thermocouples (Ø=0.25 mm) and thermocouples fixed to a steel column. Measured data were compared with calculated data applying the concept of adiabatic surface temperature. Temperatures thus obtained by finite element calculations using the softwarecode TASEF were in the good agreement with measured steel temperatures. The full scale compartment fire was conducted in a two-story concrete building. During the experiment, data were collected with PTs and thin thermocouples at different locations inside the compartment.In the new way of analyzing post-flashover compartments fires the effects of different parameters on the fire temperature development has been analyzed. The new method of analyzing the heat and mass balances of a compartment fire has made it possible to develop simple analytical as well as numerical mathematical solutions.Den här licentiatavhandlingen behandlar problem kopplade till branddynamik islutna utrymmen med tonvikt på värmeöverföring mellan gaser och utsattakonstruktioner. Avhandlingen består av en huvuddel samt fyra bilagor. Ihuvuddelen sammanfattas och diskuteras först några viktiga grundläggandeteorier och principer inom värmelära och branddynamik. Efter det presenterasett antal specialfall av brandscenarion som baseras på dessa teorier. I deavslutande bilagorna (Artiklar I-IV) finns fyra vetenskapliga artiklar somgrundligare beskriver de ovan nämnda specialfallen.Huvudfokus i avhandlingen ligger på temperaturutveckling vid brand i slutnautrymmen. Först har ett antal experiment genomförts där temperaturen mättsmed några olika typer av temperaturgivare. Sedan har ett antal försökgenomförts där den termiska exponeringen av konstruktioner kvantitativt harbestämts baserat på sådana mätningar.I avhandlingen har ett par olika brandscenarion studerats experimentellt.Framförallt behandlas den så kallade tvåzonsmodellen, där brandrummet delasin i en övre zon med höga temperaturer och en nedre med låga temperaturer.Dessutom har så kallad lokal brand studerats. I tillägg presenteras ett nytt sättatt analysera fullt utvecklade ventilationskontrollerade bränder med enenzonsmodell, där hela brandrummet antas ha en jämnt fördelad temperatur.I ett fullskale-experiment av lokal brand samlades temperaturdata in med olikatyper av plattermometrar (PT), små termoelement (TC, Ø=0.25 mm) samttermoelement fästa vid en stålbalk. Temperaturerna i stålbalken jämfördes senmed beräknade baserade på mätningar med plattermometrar och konceptetadiabatiska yttemperaturer. God överenstämmelse mellan de beräknade värdena (från finit-elementanalys med mjukvaran TASEF) och de uppmättaståltemperaturerna observerades.I tillägg har en fullskalig brand i ett slutet utrymme studerats experimentellt.Experimentet genomfördes i ett betonghus med två våningar. Under dettaexperiment uppmättes temperatur med plattermometrar och små termoelementplacerade på olika positioner i huset.Slutligen så har en ny modell för att beräkna brandtemperatur i övertändautrymmen analyserats. Både analytiska och numeriska lösningar (med hjälp avtemperaturberäkningsprogrammet TASEF) presenteras tillsammans medanalyser av bränder i slutna utrymmen med olika typer av omslutningsytor.
Godkänd; 2013; Bibliografisk uppgift: Tillkännagivande licentiatseminarium 2013-11-12 Nedanstående person kommer att hålla licentiatseminarium för avläggande av teknologie licentiatexamen. Namn: Alexandra Byström Ämne: Stålbyggnad/Steel Structures Uppsats: Fire Temperature Development in Enclosures: Some Theoretical and Experimental Studies Examinator: Professor Ulf Wickström, Institutionen för samhällsbyggnad och naturresurser, Luleå tekniska universitet Diskutant: Associate Professor Björn Karlsson, University of Island, Reykjavik Island Tid: Torsdag den 5 december 2013 kl 10.00 Plats: F1031, Luleå tekniska universitet; 20131010 (alebys)
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Clement, Jason Mark. "Experimental verification of the Fire dynamics simulator (FDS) hydrodynamic model." Thesis, University of Canterbury. Civil Engineering, 2000. http://hdl.handle.net/10092/5857.
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The objective of this research has been to verify the hydrodynamic model that is contained within the Fire Dynamics Simulator (FDS). In the first part of the research, a series of buoyant salt water experiments have been conducted, with the purpose of generating experimental data for comparison with computational fluid dynamics (CFD) models. Two types of buoyant flows have been generated in the experiments; a natural transitional flow, and flows that resemble fire induced smoke flow within a residential building. Laser Induced dye Fluorescence (LIF) has been used to measure the fluid density in a single vertical plane of the flow. Measurements have also been made of eddy frequencies on the perimeter of the transitional flows, and of the temporal development of the fire similar flow fields. The uncertainty of the experimental measurements has been quantified. In the second part of the research, the salt water experiments have been simulated with the FDS, to assess the accuracy of the hydrodynamic model. The simulations of the transitional flows are found to be highly dependent upon the resolution of the computational grid. The findings highlight the fact that the numerical methods employed in the FDS can generate fluid behaviour in the computational flow field that does not occur in the real salt water flows. This "numerical fluid behaviour" is clearly seen in the transitional flow computations, because at the source of the flow, the buoyancy and the momentum of the fluid are orientated in perpendicular directions to each other. The comparison of the computational and experimental results for the transitional flows show that the trajectory of the computed buoyant plume is steeper than the trajectory of the real salt water plume. It is speculated that the disagreement in the plume trajectory may be due to the spatial distribution of pressure within the computational domain. Due to limited computational facilities, this research has been unable to determine if the FDS hydrodynamic model can accurately compute the natural transition to turbulence. Further simulations of the transitional flows are required with grid cell dimensions that are less than the compartment height divided by 100, to determine if the transition can be correctly computed. The simulations of the fire similar flows have shown, that the FDS performs well in modelling fully turbulent flow fields, as found in residential building fires. From the fire similar flow simulations a maximum grid cell dimension, of the compartment height divided by 50, has been recommended for the simulation fire induced smoke flows within multicompartment residential scale buildings. At this recommended resolution, and resolutions coarser than this, the Smagorinsky sub-grid scale (SGS) has been found to give more accurate results than the constant viscosity SGS model. A relationship has been determined, for the minimum fluid viscosity that is required for stable computations in simulations that use the constant viscosity SGS model.
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Simms, William Ian. "An experimental investigation of axially restrained steel columns in fire." Thesis, University of Ulster, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243627.
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Scarponi, Giordano Emrys <1989>. "Experimental and analytical investigation of pressurized vessels exposed to fire." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8417/2/PhD%20thesis%20Scarponi.pdf.
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The possible occurrence of accidental fires impacting vessels for transportation and storage of hazardous materials represents a key safety issue in the process industry. In these situations, the vessel heats up, pressurizes and can fail catastrophically, generating devastating consequences. Such scenarios have been extensively investigated in the past decades to improve vessel design and emergency response planning. Numerous field studies and laboratory scale tests were carried out and several models were developed to predict the thermal and mechanical response of vessels exposed to fire. However, previous modeling approaches suffer several limitations and need to be improved and experimental data is not sufficient to effectively support the development of advanced modelling tools such as CFD.
With the aim of overcoming these limitations, a novel research program was proposed. This combines fire tests, carried out by means of an innovative experimental apparatus, and a CFD based modelling approach.
The present work focuses mainly on the modelling part (the experimental setup is briefly described and preliminary analysis of the data from tests is presented). Starting from previous approaches presented in literature, an improved CFD modelling setup was developed. Conditions of several fire tests involving LPG and water tanks were simulated and the results are compared with experimental measurements highlighting strengths and limitations of the modelling. In the last part of the work, an alternative approach is presented, based on models developed for the study of subcooled boiling flows that showed promising results in other fields of application. The aim was to explore the possibility of extending this approach to the case of fired vessels. The work proves that CFD is a powerful tool for the development of models able to accurately describe and predict the response of a pressure vessel exposed to fire. However, further work is needed especially regarding submodels for boiling.
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Edoff, Karin. "Sensory nerve fibres, neuropeptides and cartilage : experimental studies in the rat /." Linköping : Univ, 2001. http://www.bibl.liu.se/liupubl/disp/disp2001/med712s.pdf.
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MACIEL, ADRIANO DA SILVA. "EXPERIMENTAL ANALYSIS OF HIGH STRENGTH CONCRETE BEAMS REINFORCED WITH DIFFERENT FIBRES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=2131@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO futuro aponta para um crescente emprego do concreto de alto desempenho e da incorporação de fibras no concreto. O concreto de alto desempenho por suas maiores resistência e durabilidade e as fibras por conseguirem dar ductilidade e tenacidade aquele produto extremamente frágil. Recentemente foi publicada no Brasil a proposta de revisão da NBR6118, chamada de nova NB1. Nela novas relações constitutivas para o concreto estão indicadas, assim como foram modificados processos de dimensionamento. Neste trabalho foi feita a experimentação de três séries de vigas de concreto de alto desempenho nas quais foram incorporadas três tipos de fibras: aço, polipropileno e sisal. Nas peças da primeira série, a ruptura foi atingida por cisalhamento. Já as vigas das segunda e terceira séries foram concebidas de sorte a se atingir o estado limite último por flexão. Apresentam-se algumas considerações sobre o desempenho das vigas e a performance das fibras. Utiliza-se a formulação da nova NB1 para prever o comportamento das peças estruturais. Faz-se uma análise a respeito do esforço cortante resistente de cálculo e do momento fletor resistente de cálculo utilizando-se também expressões das normas Norueguesa, Canadense e Neo Zelandeza. Os resultados mostram que as fibras interferem pouco nos esforços resistentes nos estados limites últimos. As fibras de aço apresentaram ligeira e benéfica influência no esforço cortante resistente de cálculo. Também indicam que a formulação da nova NB1 pode em muitos casos ser adequada mesmo para concretos de resistência característica superiores a 50MPa, com e sem fibras. Em outros casos, como no dimensionamento ao esforço cortante, pode ser contra a segurança. As fibras de sisal promovem um esmagamento mais brando do concreto, apresentando um potencial que merece ser melhor investigado e explorado.
The future is directed to an increasing use of high performance concrete reinforced with fibers. The former due to its improved durability and strength, and the latter due to its ability to give ductility and tenacity to such a fragile product. Recently reviewed draft of the NBR 6118, called new NB1, was published. New constitutive laws for concrete and design procedures were incorporates. In this work, three series of steel reinforced high performance concrete beams with three types of fibers steel,polypropylene and sisal) were tested. The first series of beams attained shear rupture. In the second and third series, the beams were reinforced so as to attain the ultimate limit state by flexure. The behavior of the beams subjected to two point loads is discussed. The formulation presented by new NB1 to foresee the behavior of the structural elements is used. An analysis concerning shear and flexural moment design is also made using the procedures from Norway, Canada and New Zeland codes. Results show that fibers have low influence on resistant shear and moment in the ultimate limit states. The steel fibers presented a slightly and beneficial influence on the resistant shear force. The results also show the new NB1 code may in several cases be adequate to concrete with strength reaching more than 50MPa, with or without fibers. In other cases, as in shear design, it can be against safety. The sisal fibers promote a soft crushing of the concrete, presenting a potential which deserves further investigation.
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Mpanga-A-Kangaj, Christian. "Pull-out of hooked end steel fibres : experimental and numerical study." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/40820.
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Abstract
The reinforcement of concrete with steel fibres changes the failure of the composite material from catastrophic brittle failure to pseudo-ductile behaviour as a result of crack-bridging by the fibres, and the additional work which is absorbed by fibre pull-out. A good understanding of the properties of the fibre-reinforced concrete depends on an understanding of the fibre pull-out process. The main aim of the current study is to investigate, both experimentally and numerically, the pull-out behaviour of a single hooked end steel fibre from epoxy matrix, where epoxy was chosen to replace concrete in order to enable visualisation of the pull-out process. The experimental and numerical results both contribute to the development of a physical understanding of the mechanism of pull-out.
Experimental studies included the evaluation of the mechanical properties of hooked end steel fibre and epoxy matrix by means of tensile tests, the manufacturing of pull-out specimens consisting of a single hooked end steel fibre embedded in epoxy matrix, and the experimental characterisation of the fibre pull-out. The significant features (peaks and minima) of the load vs. displacement graph were correlated to stills taken from a video of the pull-out process, in which the plastic deformation of the fibre is evident. Small deformations (spalling) were also observed in the matrix. A model is proposed for the mechanisms which interact during the pull-out process.Dissertation (MEng)--University of Pretoria, 2013.
gm2014
Mechanical and Aeronautical Engineering
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Gonzalez, Ricardo Alonso. "Heurísticas afetivas no mercado de ações: um estudo quase-experimental salvador." Universidade Federal da Bahia, 2011. http://www.adm.ufba.br/sites/default/files/publicacao/arquivo/RICARDO%20ALONSO.pdf.
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O objetivo desta pesquisa foi investigar de que forma aspectos afetivos se manifestam nos julgamentos de risco e benefício nos investidores do mercado de ações brasileiro por meio da heurística afetiva. O processo decisório que conduz aos julgamentos é complexo e multifacetado, e neste trabalho pressupõe-se que o afeto assume posição privilegiada nos julgamentos. Para alcançar o objetivo pretendido criaram-se quatro estímulos em relação ao mercado de ações: alto risco; baixo risco; alto benefício; baixo benefício. A aplicação da pesquisa ocorreu em três fases, sendo uma fase de préteste, uma fase de teste (Fase 1- Teste) e uma terceira fase que se constituiu na aplicação da pesquisa propriamente dita (Fase 2 – Pesquisa). Na fase de pré-teste ajustou-se o instrumento de coleta de dados, e na Fase 1 – Teste foi feita uma pesquisa prévia com servidores da SEFAZ-BA. Essa amostra foi composta por 134 indivíduos segregados aleatoriamente em quatro grupos (um grupo para cada estímulo). Os resultados obtidos nessa fase permitiram passar para a fase seguinte. Na Fase 2 – Pesquisa aplicou-se o experimento em uma amostra composta por 143 investidores da bolsa de valores que operam por meio do home broker. A manifestação da heurística afetiva ocorreu no Grupo 2 por meio da diferença significativa de percepção de risco e de benefício antes e depois do estímulo. Para tanto, utilizou-se o teste t para médias. Em seguida, buscou-se nas variáveis idade, gênero e grau autopercebido de conhecimento do mercado de ações as determinantes da manifestação da heurística afetiva. Por meio da regressão logística múltipla identificouse que apenas a variável grau autopercebido de conhecimento do mercado de ações exerceu influência significativa na manifestação da heurística afetiva. Os resultados encontrados na pesquisa sugerem que a heurística afetiva manifesta-se mais em indivíduos com menor grau de conhecimento, e que os fatores idade e gênero não exercem influência significativa.
Salvador
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Wadleigh-Anhold, Linda L. "Fire Frequency and the Vegetal Mosaic of the Utah State University Experimental Forest." DigitalCommons@USU, 1988. https://digitalcommons.usu.edu/etd/7320.
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A fire history study conducted for the Utah State University (USU) Experimental Forest using three distinct periods of fire frequency, historic (1700-1855), settlement (1856-1909), and suppression (1910-present), showed a decreased mean fire interval (MFI) during the settlement period and a greatly increased MFI during the suppression era. The difference was attributed to the influx of ignition sources during the settlement of the nearby Cache Valley, located 40 kilometers to the west. The interaction of settlers with the resource during logging and livestock grazing activities encouraged the high MFI and created the vegetal mosaic now observed on the study area.
The elevation of the study area, 2377 m to 2651 m, places the site in the Engelmann spruce-subalpine fir zone (Picea engelmannii, Parry ex Engelm.-Abies lasiocarpa (Engelm. ex. Wats)). The suppression era and its corresponding increase in MFI has permitted the advancement of tolerant species in the understory of the intoleran lodgepole pine (Pinus contorta var. latifolia (Engelm. ex. Wats)) and aspen (Populus tremuloides Michx.). Continue suppression of disturbance from wildfire will allow the lodgepole pine cover type, which experienced the lowest MFI during the settlement period, to be further invaded by tolerant species, leading to a decrease in stand diversity and more intense fires when they do occur.
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Mortimer, Simon. "Etude de la structuration des fibres Lyocell." Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10033.
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Le but de cette these est d'etudier la formation des fibres produites a partir des solutions de cellulose dans le n-oxyde de n-methylmorpholine et de trouver des moyens pour modifier les proprietes de ces fibres, notamment leur tendance a fibriller. Dans une premiere partie, le systeme de filage de ces fibres est introduit, suivi par une explication des methodes de mesure en-ligne du developpement du diametre et de la birefringence des fibres. Ensuite, on utilise ces techniques pour suivre l'evolution de la structure d'une fibre des la filiere jusqu'a la fibre sechee. La structure finale est comparee avec celles d'autres fibres cellulosiques. Dans les quatrieme et cinquieme chapitres l'influence sur la formation de la fibre de plusieurs parametres du procede est etudie, tels que le taux d'etirage, la vitesse de filage, le diametre de la filiere et l'air entre la filiere et le bain de precipitation. Finalement, on developpe des methodes pour le filage des fibres ayant une faible tendance a fibriller, utilisant les parametres de filage, dont les plus importants sont l'air et le taux d'etirage
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Román, Cuesta Rosa María. "Human and environmental factors influencing fire trends in different forest ecosystems." Doctoral thesis, Universitat Autònoma de Barcelona, 2002. http://hdl.handle.net/10803/3646.
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La mayoría de los bosques del planeta, exceptuando, quizá, el cinturón más húmedo del trópico, han sufrido perturbaciones recurrentes por incendios, desde hace miles de años. Sin embargo, en el último siglo, la combinación de factores socio-económicos y ambientales han alterado la frecuencia y distribución de incendios en casi todos los ecosistemas forestales. Esta mala distribución del fuego ha conllevado la acumulación de este elemento perturbador en ecosistemas poco adaptados a su presencia (e.g. bosques tropicales húmedos), mientras que otros ecosistemas han sufrido los efectos de las políticas de supresión de incendios (e.g. bosques templados norteamericanos). Entre las consecuencias de estas alteraciones, algunas se refieren a variaciones en el régimen de incendios, con implicaciones en términos de conservación forestal, impacto ecológico, económico y social. La presente tesis analiza la influencia de factores ambientales y socio-económicos en algunas características del régimen de incendios en ecosistemas tropicales y mediterráneos. En el ámbito tropical, la zona de estudio es el Estado mexicano de Chiapas, y los objetivos son básicamente dos: 1) caracterizar el régimen de incendios en el Estado, en términos de frecuencia de incendios, distribución, áreas y ecosistemas afectados, tipología de incendios, causalidad, y su interacción con algunos factores como el fenómeno de El Niño, la distribución de la tenencia de la tierra o la variación de las precipitaciones. 2) Analizar la influencia relativa de factores ambientales frente a factores socio-económicos, en años de condiciones climáticas normales y años de El Niño. El objetivo último era determinar variaciones en la afectación de los principales ecosistemas y listar los factores más importantes a considerar, a nivel de gestión forestal contra incendios. A nivel de ecosistemas mediterráneos, se seleccionó el incendio del Solsonés 1998, como caso estudio, siendo los principales objetivos: 3) Seleccionar la metodología de clasificación post-incendio más eficiente entre varias técnicas analizadas (teledetección y muestreo de campo). 4) Analizar la influencia de diversos factores ambientales en la formación de islas de vegetación en un gran incendio, empleando las laderas como unidad espacial. 5) Verificar la importancia de la estructura forestal y la continuidad del combustible en la heterogeneidad final de las severidades de afectación de un incendio. En relación a estos objetivos, las principales aportaciones de este estudio han sido, en lo referente a ecosistemas tropicales: La descripción de los incendios en Chiapas como mayoritariamente superficiales, afectando principalmente a estratos no arbóreos, de grandes dimensiones, de origen antrópico y con cierta propensión a afectar zonas protegidas. La aportación clave sin embargo, hace referencia a la demostración de la importancia de El Niño en la afectación de los ecosistemas tropicales húmedos, principalmente influenciado por la presencia de pastos alrededor de bosques fragmentados. El cambio de importancia relativa de los factores ambientales en años de no-ENSO frente a la mayor importancia de los factores socio-económicos en años de ENSO. También se puede remarcar el cambio de ecosistema afectado condicionado por el tipo de año (condiciones climáticas normales o extremas, ENSO o no ENSO: pino-encino versus bosques tropicales húmedos). En relación a los bosques mediterráneos, las técnicas más sencillas de teledetección resultaron las adecuadas para la identificación de islas. La formación de estas islas se ve condicionada por el tamaño y orientación y pendiente de las laderas, así como la cantidad y madurez de los rodales afectados, siendo las laderas más extensas, de orientación noroeste, de mayor pendiente, con mayores extensiones forestales y bosques más maduros (en términos de mayores tamaños), las más propicias a formar islas. Las características estructurales de los rodales fue de gran importancia para predecir la supervivencia forestal en zonas de condiciones climáticas moderadas.The great majority of the forests of the world, excepting perhaps, the wettest belt of the tropics, have been burned over, at more or less frequent intervals, for many thousands of years. In the last century however, a combination of human and environmental factors have altered the frequency and distribution of fire, almost everywhere. This maldistribution of fire has resulted in an accumulation of this element in ecosystems not adapted to high frequencies of fire (i.e. tropical and sub-tropical areas), while other ecosystems have suffered the effects of fire suppression policies (i.e. north American temperate forests). Among the consequences of these alterations, some of them refer to variations in fire regimes, with implications in terms of forest conservation, ecological, economic and social impact. The present thesis analyses the influence of environmental and socio-economic factors for certain elements of the fire regime in tropical and Mediterranean ecosystems. In tropical areas, the study case relates to the tropical Mexican State of Chiapas, and the objectives are basically two: 1) to characterize the fire regime in the State, in terms of frequency of fires, fire distribution, areas and ecosystems affected, type of fires, causality, and their interaction with some factors like the phenomenon of El Niño, the land distribution, or the variation of rainfall values. 2) To analyse the relative influence of environmental factors versus socio-economic factors, in years of normal climatic conditions and years of El Niño. The final objective is to detect variations in the affectation of the major ecosystems and to list the most important factors to consider for forest fire management. For the Mediterranean ecosystems, the fire of Solsonés 1998 was selected as case study. Main objectives are: 3) To select the most efficient methodology for post-fire classification among several techniques: image classification and field survey. 4) To determine the influence of diverse environmental factors in the formation of vegetation islands inside a large forest fire, using "slope", as the spatial unit. 5) To verify the importance of forest structure and fuel continuity in the final heterogeneity of fire severities in a large fire. In relation to these objectives, the main contributions of this study are, with respect to tropical ecosystems: The characterization of fires in Chiapas, as in other tropical areas, mainly as superficial fires, frequently affecting non-arboreal layers. Major problems focus on large forest fires, which are responsible for the major burned areas. Fires are mainly human related and display certain propensity to affect protected zones. The key contribution nevertheless, refers to the major importance of El Niño in the affectation of humid tropical ecosystems. This is specially enhanced by the presence of cattle pasture surrounding the fragmented forests. The shift on the importance of environmental factors in years of no-ENSO versus the greater importance of socio-economic factors in years of ENSO, is also a major achievement. Moreover, shifts in ecosystem affectation have also been observed depending on the climatic conditions: pine-oak in no-ENSO years versus humid tropical forests in ENSO years. Regarding the Mediterranean forests, the simplest techniques of teledetection were the best performing ones for island identification. The formation of these islands is conditioned by the size and aspect of the slopes, as well as by the amount and maturity of the affected patches. Most extensive slopes, north-western orientations, more abrupt, larger forest extensions per slope, and more mature forests (in terms of greater sizes), are the most suitable combination of factors to form islands. This formation of islands does not have, therefore, a random distribution. Besides, the structural characteristics of the forest patches was confirmed to be of great importance to predict the forest survival in areas were fire burned under moderate climatic conditions. Larger patches and larger trees are the ones that will survive fire the best.
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Lennon, Patrick. "An experimental evaluation of the impact of ventilation opening geometry on enclosure fire severity." Thesis, University of Ulster, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248606.
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Lababidi, Issa. "Contribution à l'étude des bétons renforcés de fibres d'acier : caractérisation énergétique des dalles et poutres fléchies, analyse du comportement anisotrope d'un micro-béton de fibres orientées." Grenoble 1, 1992. http://www.theses.fr/1992GRE10045.
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La premiere partie de ce memoire consiste en une synthese bibliographique sur l'etat des connaissances a ce jour dans le domaine du beton renforce de fibres d'acier. La seconde partie developpe l'approche experimentale d'essais en laboratoire de flexion de poutres et de flexion centree de dalles carrees renforcees par differentes fibres a divers dosages. Cette etude conduit essentiellement a une analyse comparative des diverses methodes de caracterisation de l'effet de fibres a l'aide de l'enregistrement des graphes charge-deplacement et de leur exploitation. La troisieme partie concerne la mise en uvre d'un composite original constitue d'un composite original constitue d'un micro-beton fabrique a partir de couches successives de mortier et de fibres paralleles. Ces fibres sont orientees, lors de la mise en uvre du materiau, dans une direction variable par rapport aux directions de traction, compression monoaxiale et flexion pure auxquels seront ulterieurement soumis les echantillons preleves dans le materiau. Une etude experimentale detaillee est conduite sur ce materiau artificiel et une interpretation theorique est proposee
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Smith, Holly Kate Mcleod. "Punching shear of flat reinforced-concrete slabs under fire conditions." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/20962.
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This thesis examines punching shear response of reinforced-concrete flat slabs under fire conditions. The shear behaviour of concrete in fire is relatively poorly understood compared to its flexural response. Failures such as the Gretzenbach car park failure in Switzerland (2004) have prompted concerns over the punching shear capacity of flat slabs in fire. The shear behaviour of reinforced-concrete in fire depends on degradation of the individual material properties with temperature, their interaction, and more recently recognised, the effects of restrained thermal expansion. Through experimental testing this thesis aims to build a foundation understanding of the punching shear behaviour of flat reinforced-concrete slabs in fire conditions. A series of shear blocks, tested after exposure to elevated temperature (realistic fire temperature), were used to develop an understanding of the effects of elevated temperature on the shear transfer performance of reinforced-concrete. These tests allowed the complex interplay of shear-carrying mechanisms at ambient temperature to be extended to the case of post-elevated temperature. Fifteen slab-column punching shear specimens were tested under both applied load and extreme heating. In particular, the effects of restrained thermal expansion were experimentally investigated by altering the support conditions of the slab-column specimens. A purpose-built restraint frame allowed the boundary support conditions to be either fully restrained or unrestrained. This experimental series is the only series to have tested restrained specimens at elevated temperatures, though previous researchers have simulated the thermal restraint effects and reported the importance of restrained thermal expansion and curvature on the behaviour of punching shear. Parameters of slab thickness and reinforcement ratio were also varied to investigate their respective impacts on punching shear behaviour at elevated temperature. The thicker 100 mm reinforced slabs failed in punching shear, whereas the 50 mm and 75 mm thick slabs failed in flexure-shear mechanisms and the unreinforced slabs failed in flexure. Clear behavioural differences were observed between specimens with different support conditions. Unrestrained 100 mm thick slabs under sustained load failed soon after heating began, whereas none of the corresponding restrained specimens failed during heating. One restrained, heavily reinforced specimen failed during cooling, whilst under sustained load. This is the first recorded punching shear failure during the cooling phase of an elevated temperature test and may also be the first recorded test specimen ever to have failed during the cooling phase of an elevated temperature test. This failure highlights the unknown and potentially unsafe behaviour of structures during the cooling phase. Further structural investigation of the cooling behaviour of concrete flat slabs after exposure to fire, needs to be undertaken. Most of the specimens’ central deflection was away from the heat source (in the direction of loading) during the whole test, irrespective of support condition. The test setup was assessed to investigate the unusual slab-column deflection away from the heat source, however the complex behaviour observed during the tests cannot currently be explained. It is assumed that the degradation in concrete properties and non-linear material behaviour dominates over the thermal expansion of the slabs. Quantitative and qualitative comparisons are presented, though the quantitative data is impacted by size effect, non-repeatable heating application between tests and jack friction influences on specimens with low capacities. Eurocode 2 punching shear prescriptive elevated temperature design, extends the ambient temperature equation for elevated temperature use, by degrading the temperature-dependant parameters by factors. Support conditions are not considered, with the code specifically telling the designer not to consider in-plane thermal expansion effects, therefore consequently ignoring the premature punching shear failure that can occur. Furthermore, the ambient temperature equation is based on the regression of available experimental data at the time and does not consider the reinforcement as a shear transfer mechanism. The experimental capacities of the 100 mm thick, reinforced slabs that failed in pure punching shear mechanism were similar to the Eurocode 2 punching shear prescriptive design capacity, when directly compared. The unrestrained support condition was shown to be consistently, not conservatively predicted by Eurocode 2, whereas the restrained support condition capacities were conservatively predicted. It is comforting to know that the Eurocode 2 design predicts the restrained supported slabs conservatively, as real buildings are more likely to have supports closer to the restrained condition rather than the unrestrained support condition. A sensitivity analysis of the Eurocode 2 prescriptive design equation shows it is highly sensitive to the concrete strength degradation and not the variable, cp, which was used to make a support condition comparison in this thesis. This indicates how the Eurocode 2 equation for punching shear capacity lacks in its consideration of whole structural behaviour. The Critical Shear Crack Theory has been proposed as the background to a harmonised shear design approach, called Model Code 2010. The Critical Shear Crack Theory was safe in predicting the experimental punching shear capacities. There were large variances for the 100 mm thick slabs, however they are consistent with the original model comparison to test data. An expansion of the Critical Shear Crack Theory for elevated temperature requires further validation with experimental restrained thermal expansion tests, such as those presented in this thesis. Finally, a digital image correlation technique has been proven to be a reliable method to measure structural displacements of concrete at elevated temperatures. Digital image correlation allowed the crack locations and slab rotation angles to be visualized throughout testing. No other measurement techniques are able to provide similar versatility in fire testing such as that presented herein.
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Fournier, GarciÌ a. Patricia. "Surface treatment and strength of low-fired ceramic bodies: An experimental study." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277112.
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This experimental investigation examines the influence of surface treatment on the strength of low-fired tempered ceramic bodies. Specimens prepared with commercial raw materials are employed, either finger-smoothed, burnished, textured, slipped/burnished, or resin coated; two building techniques, coiling and paddle-and-anvil, are also included since these forming processes affect the vessel surface. The modulus of rupture or flexural strength is determined by means of a four-point bending test, which is sensitive to critical surface flaws. By means of a univariate analysis of variance, small differences in strength are found between ceramic briquettes with different surface treatments. Although the differences in means for the moduli of rupture values are statistically significant, the differences are of such a low magnitude that they cannot be considered behaviorally relevant. These results are only valid for the materials, mode of preparation, and test procedures employed.
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Pau, Dennis Su Wee. "A Comparative Study on Combustion Behaviours of Polyurethane Foams with Numerical Simulations using Pyrolysis Models." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2013. http://hdl.handle.net/10092/9177.
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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.
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Mohammed, U. "Experimental studies and mathematical modelling of the draping and shear deformation of woven fabrics in resin transfer moulding." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/604/.
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Hadden, Rory. "Smouldering and self-sustaining reactions in solids : an experimental approach." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5587.
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Smouldering combustion governs the burning of many materials in the built and natural environments. Smouldering is flameless, heterogeneous combustion which occurs when oxygen reacts with the surface of a solid fuel. Understanding the conditions which will result in the ignition and smouldering of a porous fuel is important and the phenomena involved are complex and coupled, involving heat and mass transfer, and chemical kinetics. This thesis reports experimental studies of the ignition, spread, suppression and emissions from reactions in porous media. Similar experimental techniques are shown in this thesis to be applicable when studying a wide range of solids which undergo self-sustaining reactions. This thesis is presented in a manuscript style. Each chapter takes the form of an independent paper which has been prepared for journal publication and as such, each chapter can stand on its own as a piece of research. A final chapter summarizes the findings and conclusions and suggests further areas of research. Chapter 1 presents a study of self-sustaining decomposition of ammonium nitrate containing inorganic fertilizer. This is of importance to the shipping industry which transports these materials in large quantities. Upon exposure to a heat source, ammonium nitrate may undergo exothermic decomposition which can propagate through the material, posing safety and economic threats. This reaction does not involve oxygenbased chemistry, but has many similarities to the propagation of a smoulder front in a porous material. Small-scale experiments to investigate the self-sustaining decomposition (SSD) behaviour of NPK (nitrogen, potassium, phosphorous) 16.16.16 fertilizer were undertaken. Experiments showed that this material will undergo self-sustaining decomposition and are used to formulate a reaction framework. Findings were applied to the events that occurred aboard the Ostedijk in 2007. Chapter 2 is a study of smoulder in polyurethane foam to study the relationship between sample size, critical heat flux and spread rate. Smouldering fires are the leading cause of residential fire deaths in developed countries and polyurethane foam is ubiquitous in the modern world. The critical heat flux for ignition was found to decrease with increasing sample size and the spread rate was found to be a function of the sample size, smoulder propagation depth and the applied heat flux. This is the first time that results on the effect of sample size on smouldering have been reported in the literature and these can be used to aid the extrapolation of small-scale flammability testing results to large scale scenarios. Chapter 3 presents an experimental investigation into the ignition of porous fuels by hot particles. This is related to the problem of spotting ember ignition in wildland fires which is a major, but poorly understood, spread mechanism. The process of spotting occurs in wildland fires when fire-lofted embers or hot particles land downwind, leading to ignition of new, discrete fires. The work studies the ignition of a fuel as a function of ember size and temperature. Metal particles are used as a proxy for burning embers and powdered cellulose to represent the forest fuel. Relationships between the size and temperature of the particle required for flaming and smouldering ignitions are found. These results are used to assess the ability of hot-spot ignition theory to determine the particle size–temperature relationship required for ignition of a cellulose fuel bed. Chapter 4 is an investigation into the suppression of smouldering coal. Subsurface coal fires are a significant global problem with fires in China alone estimated to consume up to 200 million tons of coal per year. As global demand for coal increases, accidental fires are a waste of a useful energy resource as well as a source of pollution and greenhouse gases. The results are the first attempt reported in the literature to study the suppression of these fires under controlled laboratory conditions. The ignition, spread and suppression of subsurface coal fires were studied using small-scale laboratory experiments. Time to ignition was seen to depend on particle size with small and large particles resulting in long times to ignition, while medium sized particles resulted in the shortest time to ignition. The maximum temperature, spread rate and mass lost were found to be independent of particle size above a critical particle size. The effectiveness of three systems for delivery of a suppression agent were assessed – direct injection, shower and spray. The effect of particle size on the water required for extinguishing using a spray was found to be weak. Chapter 5 presents an experimental investigation of the smouldering behaviour of peat. This is of particular interest in understanding the impact of smouldering fires on the earth system. The longer burn durations and different combustion dynamics of smouldering compared to flaming means that they have been shown to consume large amounts of biomass in, and contribute significantly to the emissions from, natural fires occurring in peatlands. The dynamics of smouldering peat in shallow, strong fronts was studied in the Fire Propagation Apparatus and a smoulder reaction framework with two burning regimes is presented. The first regime is peat smouldering and was found to be controlled by the applied heat flux and the second regime corresponded to char smouldering and was more sensitive to the flow of oxidizer. Chapter 6 complements Chapter 5 with an analysis of the CO and CO2 emissions for smouldering and flaming peat. This data can be used with large-scale measurement techniques to improve emission estimates. The emissions are found to be dependent of the burning regime and the type of combustion with flaming resulting in higher fluxes of CO2 and lower fluxes of CO compared to peat smouldering. Char smouldering resulted in the highest yields of CO and CO2. The large majority of emissions (85% of CO2 and 97% of CO) are released during the smoulder phase of the reaction. This highlights the differences in the chemical processes occurring under these two modes of combustion. Chapter 7 summarizes the research undertaken in this thesis and presents possible further work.
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Rojek, Jan. "Effect of voids in thick-walled pressure vessels : Experimental observations and numerical modelling." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM015.
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Dans cette thèse, on analyse l'effet de la porosité sur le comportement mécanique d'un matériau composite à fibres de carbone utilisé dans le cadre d'applications à hautes performances. Les réservoirs hyperbare destinés au stockage de l'hydrogène en sont un exemple. Du fait de leur fabrication par enroulement filamentaire, ces structures à parois épaisses présentent des taux de porosité parfois très élevés. La conséquence de telles porosités sur la durabilité des réservoirs et plus largement sur des structures composites chargées de manière multi-axiale est très peu documentée. Les travaux présentés ici s'inscrivent par ailleurs dans le développement d'un modèle existant à MINES ParisTech et ayant fait ses preuves pour prédire la résistance de composites unidirectionnels. Il s'agit ici de perfectionner ce modèle en intégrant de nouveaux facteurs comme les porosités. Des observations (tomographie aux rayons X et microscopie optique) d'un réservoir sont réalisées afin de caractériser les vides et leur distribution au sein de la structure. En parallèle, une étude expérimentale est conduite sur des éprouvettes à différents taux de porosité. La résistance de ces éprouvettes, chargées simultanément en traction longitudinale et compression transverse, est évaluée grace à un système expérimental spécialement conçu. A des échelles encore plus fines, des essais sont réalisés sur des échantillons d'époxy entaillés pour caractériser la croissance des cavités microscopiques et le comportement mécanique de la résine sous un état des contraintes multi-axial. Toutes ces données expérimentales sont ensuite exploitées et intégrées dans le modèle numérique afin de simuler le comportement à rupture d'un réservoir à parois épaissesThe topic of this thesis is the influence of voids on the mechanical properties of carbon fibre reinforced polymers used in high performance applications, such as pressure vessels for hydrogen storage. Manufactured through filament winding, these thick-walled structures can show a significant void content. The effect of these voids on the strength of pressure vessels and, more in general, on the strength of composite structures subjected to multiaxial loads, is not thoroughly understood. The work presented in this thesis is carried out in the context of an existing model of tensile failure of unidirectional composites developed at MINES ParisTech. The objective of the work presented here is to take into account additional factors, such as void content. X-ray tomography and optical microscopy observations are carried out to characterize voids in a carbon-epoxy pressure vessel. In another experimental study, mechanical tests are performed on carbon-epoxy specimens with different levels of void content. The influence of a biaxial load (longitudinal tension and through-thickness compression) is evaluated using a custom-designed experimental setup.At the microscopic scale, tests on notched epoxy specimens are carried out to investigate microscopic void growth and the mechanical behaviour of the resin under a multiaxial stress state. Finally, a numerical approach to modelling failure of a thick-walled cylinder is proposed in the framework of the multiscale fibre break model, taking into account the experimental observations
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Plucinski, Matthew Paul Mathematics & Statistics Australian Defence Force Academy UNSW. "The investigation of factors governing ignition and development of fires in heathland vegetation." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Mathematics and Statistics, 2003. http://handle.unsw.edu.au/1959.4/38702.
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Heathlands typically experience regimes consisting of frequent and intense fires. These fire regimes play important roles in the lifecycles and population dynamics of all species in these communities. Prescribed fire is commonly applied to heathlands to minimise the risk of wildfires as well as to promote biodiversity. Ignitions in heathlands tend to either be unsustainable, or quickly develop into rapidly spreading intense fires. This presents a major problem for the application of prescribed fire and is the primary focus of this thesis. Heathland ignition has been investigated in three sections; litter ignition; vertical development of fire into the shrub layer; and horizontal spread through the shrub layer. These were studied in laboratory experiments using miniature versions of field fuels. Ignition success in litter layers was related to the dead fuel moisture content. Litter type, ignition source, and presence of wind were found to affect the range of ignitable fuel moisture contents of a litter bed. The effect of litter type was best explained by density. Dense litter beds required drier conditions for ignition than low density litter beds. The vertical development of fire into shrubs was mostly dependent on live fuel moisture content, but crown base height, presence of wind, ignition source, shrub height and the percentage of dead elevated fuel were also important. Horizontal spread of fires through shrub layers was most affected by the presence of a litter layer, with nearly all ignitions successful when there was an underlying litter fire. Fire spread would only occur in shrubs without a litter layer when the shrub layer was dense and dry, or had a substantial dead fuel component. Spread was more likely to be sustained when there was wind. Models predicting the moisture content of dead fuels were tested in heathlands, and as would be expected those that can be calibrated for different fuel types were found to have the best performance. Fuel moisture content and fuel load models were reviewed for heathlands, and a number of recommendations for future research were made.
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Sundman, Ola. "Cation adsorption properties of substituted kraft fibres : an experimental and thermodynamic modelling study." Doctoral thesis, Umeå universitet, Kemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1891.
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Acid/base and metal ion adsorption properties have been investigated for a range of chemically modified bleached Kraft fibre materials (pulps). The studies were performed via potentiometric titrations, Flame Atomic Absorbtion (and Emission) Spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy and Extended X-ray Absorbtion Fine Structure measurements. As a result of a chemical modification procedure, the total concentration of acidic carboxylate groups in the fibre materials ranged between 43 and 590 μmol/g. The preferable surface potential model for modelling the ionic strength dependent acid/base properties of fibre materials with low charge densities, i.e. unmodified fully bleached Kraft fibre materials, was found to be the Basic Stern Model. For fibre materials with high total charge, ≳100 μmol/g, this model resulted in poor fits to data, and for such materials a number of Constant Capacitance Models, one at each ionic strength, must be recommended. With respect to metal ion adsorption, the results have indicated that the unspecific Donnan theory could correctly model the simultaneous adsorption of several metal ions, i.e. K+, Na+, Mg2+, Ca2+ and Cu2+, provided that the salt concentration in the fibre suspension is low. In suspensions of high salt concentration it was, however, found that this very same model strongly underestimated the adsorption of Ca2+ and Cu2+. Here, the Donnan model had to be complemented by specific ion exchange equilibria. These results were corroborated by spectroscopic evidence of specific interactions between Cu2+-ions and fibres. The spectroscopic indication of a complex formed between two fibre surface carboxylate groups and one Cu2+-ion, agree with the specific ion exchange model. It was therefore concluded that specific metal ionfibre interactions cannot be neglected, especially at high salt concentrations. The interactions occurring between the polycation GaO4Al12(OH)24(H2O)127+ and fibre materials were studied by both adsorption and spectroscopic measurements. These indicate that GaO4Al12(OH)24(H2O)127+ is surprisingly stable in fibre suspensions and that intact GaO4Al12(OH)24(H2O)127+- ions are strongly adsorbed onto the fibres. Also for this ion, specific interactions has to be considered, since the strong adsorption registered was too strong to be explained by Donnan equilibria. In the thesis, the stochiometric composition and an equilibrium constant characterising these interactions is presented.
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Schudy, Simeon [Verfasser]. "Experimental studies on cooperation and coordination in politics, firms and society / Simeon Schudy." Konstanz : Bibliothek der Universität Konstanz, 2012. http://d-nb.info/1020366184/34.
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