Dissertations / Theses on the topic 'Fire Loading'
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Pirzadeh, Davoud [Verfasser]. "Analysis of framed structures under fire loading / Davoud Pirzadeh." Wuppertal : Universitätsbibliothek Wuppertal, 2019. http://d-nb.info/1190649608/34.
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Jeffers, Ann E. "A Fiber-Based Approach for Modeling Beam-Columns under Fire Loading." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/38692.
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The work described herein emphasizes a new fiber-based approach to modeling the response of structural frames subjected to realistic fire conditions. The proposed approach involves the development and validation of two finite elements that can be used collectively to simulate the thermal and mechanical response of structural frames at elevated temperatures. To model the thermal response, a special-purpose fiber heat transfer element is introduced. The first of its kind, the fiber heat transfer element uses a combination of finite element and finite difference methods to provide an accurate and highly efficient solution to the three-dimensional thermal problem. To simulate the mechanical response, a flexibility-based fiber beam-column element is used. The element presented here extends the formulation of Taucer et al. (1991) to include thermal effects, geometric nonlinearities, and residual stresses.
Both fiber elements are implemented in ABAQUS (2007) using the user-defined element (UEL) subroutine. The element formulations are verified by analyses of benchmark experimental tests and comparisons with traditional finite elements. Results indicate that both elements offer superior accuracy and computational efficiency when compared to traditional methods of analysis. Analyses of structures subjected to non-uniform heating emphasize the advantages of the fiber-based approach.
To demonstrate a realistic application of the proposed approach, the work concludes with an investigation of the response of unprotected steel beams subjected to localized fires. Because realistic fires are considered, the treatment of strain reversal upon cooling is also addressed. The analyses are used to demonstrate that the standard fire test is generally unconservative at predicting the time at failure of a structure subjected to realistic fire conditions, since failure depends more on the evolution of temperatures within the steel beams than the duration of fire exposure. The analyses also show that critical temperatures from the standard fire test are conservative and thus offer a better means for predicting failure in steel structures within the scope of the standard fire test.Ph. D.
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Fogle, Emily Johanna. "Compression Failure of Aluminum Plates Exposed to Constant Heat Flux." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/33011.
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Aluminum is used as a structural member in marine applications because of its low weight. One challenge is to design against failure of aluminum structures in fire. A parametric study was performed to quantify the effects of parameters on the compression failure of aluminum plates during a fire. A thermo-structural apparatus was designed to perform compression tests on aluminum samples consisting of a compression load frame, a hydraulic system, and electric heaters.
The effect of dimensional variation on failure behavior was examined. Aluminum 5083 and 6082 alloys were tested with three thicknesses, two lengths and two widths. Three heat fluxes and various buckling stresses were used. Micro Vickerâ s hardness values were measured before and after testing to quantify the effect of heating on the strength of the aluminum.
In general, lower applied stress resulted in higher failure temperature and longer time to failure. Dimensional variations had a negligible effect on failure behavior. The 5083 alloy has a minimum stress level of 50% of the buckling stress at 10kW/m2 and 10% of the buckling stress at 20kW/m2, while the 6082 alloy has a minimum stress level of 75% of the buckling stress at 10kW/m2 and 25% of the buckling stress at 20kW/m2. The 6082 failed at higher temperatures and longer failure times than the 5083. The presence of insulation on the exposed surface decreased the temperature rise, resulting in longer failure times. Vickerâ s hardness decreased with heating in general. The results describe the effects of parameters of the failure of aluminum.Master of Science
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Tsolakis, Thomas. "Thermal response analysis of process vessels in the presence of fire loading." Thesis, Imperial College London, 1997. http://hdl.handle.net/10044/1/8858.
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Ab, Kadir Mariyana Aida. "Fire resistance of earthquake damaged reinforced concrete frames." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7969.
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The topic of structural damage caused by fires following an earthquake (FFE) has been discussed extensively by many researchers for over a decade in order to bring the two fields closer together in the context of performance based structural engineering. Edinburgh University, Heriot-Watt University, Indian Institute of Technology Roorkee (IIT Roorkee) and Indian Institute of Science initiated a collaboration to study this problem under a UK-India Engineering Research Initiative (UKIERI) funded project. The first construction of a single-storey reinforced concrete frame at IIT Roorkee was completed in summer 2011; this is known as the Roorkee Frame Test 1 throughout this thesis. This thesis presents the modelling of the Roorkee Frame Test 1 using the finite element method and assesses the capability of the numerical methodologies for analysing these two sequential events. Both two and three dimensional finite element models were developed. Beam and shell elements were chosen for the numerical modelling, which was carried out using the general purpose finite element package ABAQUS (version 6.8). The variation in material properties caused by these two types of loading, including strength and stiffness degradation, compressive hardening, tension stiffening, and thermal properties, is implemented in the numerical modelling. Constitutive material calculations are in accordance with EC4 Part 1.1, and all loading is according to IS 1893:2002 Part 1 (Indian Standard). The time-temperature curve used in the analysis is based on data from the test carried out. The behaviour of the Roorkee Frame Test 1 when subjected to monotonic, cyclic lateral loading followed by fire is presented. The capacity of the frame when subjected to lateral loading is examined using a static non-linear pushover method. Incremental lateral loading is applied in a displacement-controlled manner to induce simulated seismic damage in the frame. The capacity curve, hysteresis loops and residual displacements are presented, discussed and compared with the test results. The heat transfer analysis using three dimensional solid elements was also compared against temperature distributions recorded during the Roorkee frame fire test. Based on the smoke layer theory, two emissivity values were defined. In this study, the suitability of numerical modelling using ABAQUS to capture the behaviour of Roorkee frame test is examined. The results from this study show that the 3D ABAQUS model predicted more reliable hysteresis curves compared to the 2D ABAQUS model, but both models estimated the lateral load capacity well. However neither model was able to simulate the pinching effect clearly visible in the hysteresis curves from the test. This was due to noninclusion of the bond slip effect between reinforcing bars and concrete. The residual displacement obtained at the end of the cyclic lateral loading analysis from the 2D ABAQUS model is higher than that seen in the test. However, the result in the 3D ABAQUS model matched the trend obtained in the test. The both columns appear to stiffen under the heating and the residual displacement seems to recover slightly. Lateral displacements, obtained in the thermo-mechanical analysis of the numerical models, show that thermal expansion brings the frame back towards its initial position. Finally, correlation studies between analytical and experimental results are conducted with the objective to establish the validity of the proposed model and identify the significance of various effects on the local and global response of fire resistance earthquake damaged of reinforced concrete frames. These studies show that the effect of tension stiffening and bond-slip are very important and should always be included in finite element models of the response of reinforced concrete frame with the smeared crack model when subjected to lateral and thermal loading. The behaviour of reinforced concrete frames exposed to fire is usually described in terms of the concept of the fire resistance which defined in terms of displacement limit. This study shows the global displacement of the frame subjected to fire recover slightly due to the thermal expansion during the heating.
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Arthur, Katherine Marie. "Predicting the Failure of Aluminum Exposed to Simulated Fire and Mechanical Loading Using Finite Element Modeling." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/32670.
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The interest in the use of aluminum as a structural material in marine applications has increased greatly in recent years. This increase is primarily due to the low weight of aluminum compared to other structural materials as well as its ability to resist corrosion. However, a critical issue in the use of any structural material for naval applications is its response to fire.
Past experience has shown that finite element programs can produce accurate predictions of failure of structural components. Parameter studies conducted within finite element programs are often easier to implement than corresponding studies conducted experimentally.
In this work, the compression-controlled failures of aluminum plates subjected to an applied mechanical load and an applied heat flux (to simulate fire) were predicted through the use of finite element analysis. Numerous studies were completed on these finite element models. Thicknesses of the plates were varied as well as the applied heat flux and the applied compressive stresses. The effect of surface emissivity along with the effect of insulation on the exposed surface of the plate was also studied. The influence of the initial imperfection of the plates was also studied. Not only were the physical conditions of the model varied but the element type of both the solid and shell models as well as the mesh density were also varied. Two different creep laws were used to curve fit raw creep data to understand the effects of creep in the buckling failure of the aluminum plates.
These predictions were compared with experiments (from a previous study) conducted on aluminum plates of approximately 800mm in length, 200mm in width, 6-9mm in thickness and clamped at both ends to create fixed boundary conditions. A hydraulic system and a heater were used to apply the compressive load and the heat flux respectively. Comparisons between predicted and experimental results reveal that finite element analysis can accurately predict the compression-controlled failure of aluminum plates subjected to simulated fire. However, under certain combinations of the applied heat flux and compressive stress, the mesh density as well as the choice of element may have a significant impact on the results. Also, it is undetermined which creep curve-fitting model produces the most accurate results due to the influence of other parameters such as the initial imperfection.Master of Science
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Manu, Christopher Corneliu. "Finite element analysis of stress rupture in pressure vessels exposed to accidental fire loading." Thesis, Kingston, Ont. : [s.n.], 2008. http://hdl.handle.net/1974/1295.
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Kolaks, Jeremy. "Fuel loading and fire behavior in the Missouri Ozarks of the Central Hardwood Region /." free to MU campus, to others for purchase, 2004. http://wwwlib.umi.com/cr/mo/fullcit?p1420928.
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Escobedo, Montoya Francisco Javier 1969. "Fire frequency effects on fuel loading in pine-oak ecosystems of the Madrean Province." Thesis, The University of Arizona, 1998. http://hdl.handle.net/10150/291850.
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There is increasing interest in the use of prescribed fire to reduce fuel loadings and other management objectives in ecosystems of the Madrean Province. Fuel loadings were measured on the same pine-oak ecosystem occurring on five different sites with a range of different fire frequencies. To determine the effects of fire frequencies on fuel loading. Study sites located in Mexico were characterized by a high fire frequency. Study sites in the United States were characterized by low and intermediate fire frequencies. Heavy fuel loadings on sites with high fire frequencies were below the recommended amounts for coarse woody debris. Sites with intermediate fire frequencies were within recommended amounts of coarse woody debris while sites with low fire frequencies were above recommended amounts for coarse woody debris. There was no difference in fine fuel loading among sites with 2, 5, 9, and 13 fires since 1900. Total fuel loading was inversely related to fire frequency. The effects of intermediate fire frequencies can be used to assess ecosystem function and meet multiple use management objectives.
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Summers, Patrick T. "Predicting Compression Failure of Fiber-reinforced Polymer Laminates during Fire." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/32770.
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A thermo-structural model was developed to predict the failure of compressively loaded fiber-reinforced polymer (FRP) laminates during fire. The thermal model was developed as a one-dimensional heat and mass transfer model to predict the thermal response of a decomposing material. The thermal properties were defined as functions of temperature and material decomposition state. The thermal response was used to calculate mechanical properties. The structural model was developed with thermally induced bending caused by one-sided heating. The structural model predicts out-of-plane deflections and compressive failure of laminates in fire conditions. Laminate failure was determined using a local failure criterion comparing the maximum combined compressive stress with the compressive strength.
Intermediate-scale one-sided heating tests were performed on compressively loaded FRP laminates. The tests were designed to investigate the effect of varying the applied stress, applied heat, and laminate dimensions on the structural response. Three failure modes were observed in testing: kinking, localized kinking, and forced-response deflection, and were dependent on the applied stress level and independent of applied heating. The times-to-failure of the laminates followed an inverse relationship with the applied stress and heating levels. The test results were used to develop a relationship which relates a non-dimensionalized applied stress with a non-dimensionalized slenderness ratio. This relationship relates the applied stress, slenderness ratio, and temperature of the laminate at failure and can be used to determine failure in design of FRP laminate structures. The intermediate-scale tests were also used to validate the thermo-structural model with good agreement.Master of Science
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Miah, Md Jihad. "The effect of compressive loading and cement type on the fire spalling behaviour of concrete." Thesis, Pau, 2017. http://www.theses.fr/2017PAUU3015/document.
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La recherche présentée dans cette thèse vise à examiner le mécanisme d’écaillage des bétons exposés au feu et comprendre l’influence du chargement mécanique appliqué en compression durant le chauffage. Des cubes (200 x 200 x 200 mm3) et des dalles (800 x 800 x 100 mm3) de béton fabriqués avec des ciments CEM II et CEM III (B40-II et B40-III: fc28days ≈ 40 MPa) ont été exposés à un feu ISO 834-1 sous différents niveaux de chargement uniaxial (cubes) et biaxial (dalles). En outre, l'effet du chargement mécanique (pression de confinement et charge uniaxiale) sur la perméabilité résiduelle au gaz a été étudié. Afin de mieux analyser les résultats expérimentaux et comprendre les mécanismes à l’origine de l'écaillage, des calculs numériques ont été réalisés en utilisant un modèle thermo-mécanique du code aux éléments finis CAST3M. Les résultats expérimentaux ont clairement montré que les éprouvettes chargées (uniaxial et biaxial) présentent un risque d’écaillage plus important que les éprouvettes non chargées. L’écaillage augmente avec le niveau de contrainte appliquée. Une partie des essais mais pas tous, ont montré que le B40-II (3% de laitier) présente un écaillage plus important que celui du béton B40-III (43% de laitiers).À partir de cette étude sur deux bétons ordinaires, il peut être mis en évidence qu'un certain niveau de contrainte de compression externe (uniaxiale ou biaxiale) est nécessaire pour induire l'écaillage du béton ordinaire. Les pressions des pores se combine avec les contraintes thermiques dûes aux gradients thermiques. Les contraintes de compression appliquées empêchent la création de certaines fissures générées par l'incompatibilité des déformations thermiques de la pâte de ciment et des granulats et des gradients thermiques. Pour l'échantillon non chargé, la création de fissures augmente la perméabilité et empêche naturellement le développement des pressions de pores.Pendant un feu réel, les membres structurels en béton sont toujours chargés ou retenus. La présence d'un chargement compressif pendant le chauffage augmente considérablement le stress de compression (diminue le stress de traction) et la grandeur de la pression des pores, ce qui augmente le risque d'écaillage. Ensuite, le stress compressif appliqué est un facteur clé très important que la conception de la résistance au feu des structures en béton devrait prendre en compte lors de l'écaillage. Par conséquent, il est recommandé que les essais d'écaillage ne soient pas effectués uniquement sur des échantillons non chargésThe research presented in this thesis seeks to examine and understand the mechanism of fire spalling role played by the external compressive loading during heating. Concrete cube (200 x 200 x 200 mm3) and slab (800 x 800 x 100 mm3) specimens made with CEM II and CEM III cements (B40-II and B40-III: fc28days ≈ 40 MPa) were exposed to ISO 834-1 fire curve under different levels of external uniaxial (for cube) and biaxial (for slab) compressive stress. Additionally, the effect of external compressive loading (confining pressure and uniaxial load) on the residual gas permeability of concretes have been investigated. In order to better analyse the experimental results and to provide more insight into the mechanism behind the fire spalling behaviour of concrete, numerical computations were carried out by using the existing thermo-mechanical model implemented in a finite element code CAST3M. The experimental results have clearly shown that the loaded specimens (uniaxial and biaxial) are more prone to spalling than unloaded specimens, with increasing amounts of spalling for higher values of applied compressive stress. Part of the tests, but not all have shown that B40-II (3% of slag) exhibited higher spalling than the B40-III (43% of slag).From this study on two ordinary concretes, it highlights that a certain level of external compressive stress (uniaxial or biaxial) was necessary to induce spalling. A possibility is that the applied compressive stress prevents the creation of cracks naturally due to thermal mismatch between cement paste and aggregates and thermal gradients. For unloaded specimen, the creation of cracks increases the permeability and naturally prevents the pore pressure to exceed a value that favours spalling.During a real fire, concrete structural members are always loaded or restrained. The presence of compressive loading during heating significantly increases the compressive stress (decreases the tensile stress) and the magnitude of pore pressure, which increase the risk of fire spalling. Then, the applied compressive stress is a very important key factor that the fire resistance design of concrete structures should take into account when considering spalling. Hence, it is recommended that the fire spalling test should not be carried out only on unloaded specimens, especially for the ordinary concrete
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Mansour, Khalid A. "Fires in large atmospheric storage tanks and their effect on adjacent tanks." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/12196.
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A suite of models were integrated to predict the potential of a large liquid hydrocarbon storage tank fire escalating and involving neighbouring tanks, as a result of thermal loading. A steady state pool fire radiant heat model was combined with a further model, in order to predict the distribution of thermal loading over the surface of an adjacent tank, and another model was incorporated to predict the thermal response of the contents of the adjacent tank. In order to predict if, or when, an adjacent tank will ignite, the radiant heat from the fire received by the adjacent tank must be quantified. There are a range of mathematical models available in the literature to calculate the radiant heat flux to a specified target and each of these models is based on assumptions about the fire. The performance of three of these models, which vary in complication, was analysed (the single point source model, the solid flame model and the fire dynamics simulator computational fluid dynamics model) and, in order to determine the performance of each model, the predictions made by each of the models were compared with actual experimental measurements of radiant heat flux. Experiments were undertaken involving different liquid fuels and under a range of weather conditions and, upon comparing the predictions of the models with the experimental measurements, the solid flame model was found to be the one most appropriate for safety assessment work. Thus, the solid flame model was incorporated into the thermal loading model, in order to predict the distribution of radiant heat flux falling onto an adjacent tank wall and roof. A model was developed to predict the thermal response of the contents of an adjacent tank, in order to predict variations in the liquid and vapour temperature, any increase in the vapour space pressure and the evolution of the vapours within the given time and the distribution of thermal loading over the surface of the tank as predicted by previous models; of particular importance was the identification of the possibility of forming a flammable vapour/air mixture outside the adjacent tank. To assess the performance of the response model, experiments were undertaken at both laboratory and field scale. The laboratory experiments were conducted in the Chemical Engineering Laboratory at Loughborough University and required the design and construction of an experimental facility representing a small-scale storage tank exposed to an adjacent fire. The field scale experiments were undertaken at Centro Jovellanos, Asturias, Spain. An experimental vessel was designed and fabricated specifically to conduct the laboratory tests and to measure the response of a tank containing hydrocarbon liquids to an external heat load. The vessel was instrumented with a network of thermocouples and pressure transmitter and gauge, in order to monitor the internal pressure and distribution in temperature throughout the liquid and its variation with time. The model predicting the thermal response of an adjacent tank was shown to produce predictions that correlated with the experimental results, particularly in terms of the vapour space pressure and liquid surface temperature. The vapour space pressure is important in predicting the time when the vacuum/pressure valve opens, while the liquid surface temperature is important as it governs the rate of evaporation. Combining the three models (the Pool Fire model, the Thermal Loading model and the Response model) forms the basis of the storage tanks spacing international codes and presents a number of innovative features, in terms of assessing the response to an adjacent tank fire: such features include predicting the distribution of thermal load on tanks adjacent to the tank on fire and thermal load on the ground. These models can predict the time required for the opening of the pressure vacuum relief valve on adjacent tanks and the release of the flammable vapour/air mixture into the atmosphere. A wide range of design and fire protection alternatives, such as the water cooling system and the minimum separation distance between storage tanks, can be assessed using these models. The subsequent results will help to identify any recommended improvements in the design of facilities and management systems (inspection and maintenance), in addition to the fire fighting response to such fires.
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Hammond, Sean LaRoy. "Mapping Fire Fuels Through Detection of Canopy Biomass Loading In Juniper, Sagebrush, and Gambel Oak Communities." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1194.
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Every year, millions of acres of forest and rangeland are burned in prescribed burns as well as wildfires. The costs associated with wildfires may be some of the largest we face as a society both in material goods and in life. The importance of managing fire fuels has increased with the development of the wildland-urban interface. With this increased emphasis has come the development of tools to assess, map, and simulate fuel maps at a landscape level. These fuel maps are then input into computer-aided wildfire simulation models that are used by land managers in the planning process. A current challenge for land managers is to find efficient ways to measure the amount and structure of fire fuels on a landscape level. Fuel models are one of the required inputs for software that mathematically computes wildfire rate of spread. Various methods have been used to develop fuel maps. It is the objective of this thesis to develop a method by which fuel models can be predicted and mapped on a landscape level through utilization of remotely sensed data. The proposed process for this method is: 1) develop landcover classification, 2) assess data analysis approaches for use in creation of predictive regression models, 3) correlation of data results to Natural Fuels Photo Series, and 4) translate Natural Fuels Photo Series classifications into fuel models described by Scott and Burgan.
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Крутиголова, Богдан Іванович, and Bohdan Krutyholova. "Медичний реабілітаційний цент в місті Одеса з комп’ютерним моделюванням пожежної стійкості." Thesis, Тернопільський національний технічний університет імені Івана Пулюя, 2017. http://elartu.tntu.edu.ua/handle/123456789/19286.
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Роботу виконано на кафедрі будівельної механіки Тернопільського національного технічного університету імені Івана Пулюя Міністерства освіти і науки України.
Захист відбудеться 22 лютого 2017 р. о 10.00 годині на засіданні екзаменаційної комісії №1 у Тернопільському національному технічному університеті імені Івана Пулюя за адресою: 46001, м. Тернопіль, вул. Руська, 56, навчальний корпус №2, ауд. 35.Виконано аналіз та порівняння відомих методів і нормативних документів щодо дослідження вогнестійкості будівельних конструкцій та розроблено проект медичного реабілітаційного центру з врахуванням забезпечення пожежної стійкості. Шляхом комп’ютерної симуляції пожежі одержано розподіл теплового навантаження на об’єкт, концентрації шкідливих газів (CO, CO2), задимленості. Виявлено розподіл температур на поверхні та по товщині несучих елементів конструкції при пожежі, виконано оцінку їх впливу на НДС елементів конструкції.
In this graduation paper the analysis and comparison of the known methods and regulations regarding research of fire resistance of structures were performed. Project of the the medical rehabilitation center was developed taking into account it’s structures fire resistance. Through computer simulations of fire the distributions of heat loadings on the object, concentration of harmful gases (CO, CO2) and smoke were received. Temperature distribution on the surface and the thickness of bearing structural elements during a fire was discovered and the estimation of their influence on the stress-strain state of designed elements was performed.
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Boyd, Steven Earl. "Compression Creep Rupture of an E-glass/Vinyl Ester Composite Subjected to Combined Mechanical and Fire Loading Conditions." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/29896.
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Polymer matrix composites are seeing increasing use in structural systems (e.g. ships, bridges) and require a quantitative basis for describing their performance under combined mechanical load and fire. Although much work has been performed to characterize the flammability, fire resistance and toxicity of these composite systems, an understanding of the structural response of sandwich type structures and laminate panels under combined mechanical and thermal loads (simulating fire conditions) is still largely unavailable. Therefore a research effort to develop a model to describe the structural response of these glass/vinyl esters systems under fire loading conditions is relevant to the continuing and future application of polymer matrix composites aboard naval ships.
The main goal of the effort presented here is to develop analytical models and finite element analysis methods and tools to predict limit states such as local compression failures due to micro-buckling, residual strength and times to failure for composite laminates at temperatures in the vicinity of the glass transition where failure is controlled by viscoelastic effects. Given the importance of compression loading to a structure subject to fire exposure, the goals of this work are succinctly stated as the:(a)Characterization of the non-linear viscoelastic and viscoplastic response of the E-glass/vinyl ester composite above Tg. (b)Description of the laminate compression mechanics as a function of stress and temperature including viscoelasticity.(c)Viscoelastic stress analysis of a laminated panel ([0/+45/90/-45/0]S) using classical lamination theory (CLT).
Three manuscripts constitute this dissertation which is representative of the three steps listed above. First, a detailed characterization of the nonlinear thermoviscoelastic response of Vetrotex 324/Derakane 510A - 40 through Tg was conducted using the Time - Temperature - Stress - Superposition Principle (TTSSP) and Zapas - Crissman model. Second, the modeling approach and viscoelastic relaxation mechanism is validated by substituting the shear relaxation modulus into a compression strength model to predict lifetimes for isothermal and one sided heating of unidirectional laminates. Finally, viscoelastic stress analysis using CLT is performed for a general laminated panel to predict lifetimes under one sided heating. Results indicate that when temperatures remain in the vicinity of Tg, the laminate behavior is controlled by thermoviscoelasticity.Ph. D.
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Lacković, Luka [Verfasser], and Joško [Akademischer Betreuer] Ožbolt. "Behavior of concrete structures subjected to static and dynamic loading after fire exposure / Luka Lacković ; Betreuer: Joško Ožbolt." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2021. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-ds-117011.
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Shakespear, Alan Wyatt. "Fuel Response to Mechanical Mastication of Pinyon-Juniper Woodlands in Utah." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4317.
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Pinyon-juniper woodland encroachment threatens ecosystem function and diversity on sagebrush steppe. Decreased fire frequency likely favors proliferation of pinyon-juniper woodlands and subsequent decline in desirable understory species. Increased tree cover produces hazardous canopy fuel loads that contribute to severe crown fires and threaten life and property at the wildland-urban-interface. Mechanical mastication converts large canopy fuels into small woody debris, altering wildfire dynamics from a potential crown fire to a more controllable surface fire. We measured fuel loading and cover on untreated, masticated, and masticated + burned treatments on 30-m transects within 30 X 33-m subplots, representing 45 different sites throughout Utah. All variables were analyzed using mixed-model analysis of covariance with untreated or pretreatment tree cover as the covariate. Shredding trees reduced large-diameter fuels to primarily 10-hour fuels (6.4-25.4 mm diameter). Reduced fuel sizes, fuel redistribution, and fuelbed compactness resulting from mastication treatments can aid wildfire suppression. Masticated + burned treatments effectively reduced woody surface fuel loading to that of pretreatment conditions. Prescribed burning could be used outside the growing season in cool-weather, high-moisture conditions to remove surface fuels, mitigating lethal soil heating and plant mortality. Shrub loading was not adversely affected by mastication treatments, but was significantly reduced with masticated + burned treatments. Masticated and masticated + burned treatments significantly increased herbaceous fuel loading. Treating at lower tree cover values reduced fuel buildup, and provided more opportunity for a positive herbaceous response. Fuel loading estimates measured in this study were provided to populate fire behavior models for mastication treatments on our study sites when such models become available.
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Galgamuwe, Arachchige Pabodha Galgamuwa. "Ecological restoration of an oak woodland in Kansas informed with remote sensing of vegetation dynamics." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/38196.
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Doctor of PhilosophyDepartment of Horticulture, Forestry, and Recreation Resources
Charles J. Barden
Recurrent, landscape-level fires played an integral part in the development and persistence of eastern oak (Quercus spp.) forests of the United States. These periodic surface fires helped secure a competitive position for oaks in the regeneration pool by maintaining a desirable species composition and forest structure. This historical fire regime was altered with the European settlement of North America, and fire suppression within forestlands became a standard practice since 1930s. With decades of fire suppression, mature oak-dominated woodlands have widely converted to shade-tolerant tree species. Prescribed fire has successfully been used to enhance oak regeneration in eastern forests. However, oak woodland restoration within the forest-prairie ecotone of the Central plains has not been systematically studied. Fuel beds under shade-tolerant species are often less conducive to fire. Therefore, monitoring fuel loading (FL) and its changes are essential to inform management decisions in an oak regeneration project. Rapid expansion of eastern redcedar (Juniperus virginiana/ERC) is another ecological issue faced by land managers throughout North America’s midcontinent forest-prairie ecotone. Hence, it is worthy to monitor ERC expansion and effects on deciduous forests, to inform oak ecosystem restoration interventions within this region. Therefore, the main objectives of this dissertation were three-fold: (1) understand the effects of prescribed burning and mechanical thinning to encourage oak regeneration; (2) investigate the initial effects of an oak regeneration effort with prescribed fire and mechanical thinning on FL; and (3) monitor the spatio-temporal dynamics of ERC expansion in the forest-prairie ecotone of Kansas, and understand its effects on deciduous forests. The first two studies were conducted on a 90-acre oak dominated woodland, north of Manhattan, Kansas. The experimental design was a 2 (burn) x 2 (thin) factorial in a repeated measures design. The design structure allowed four treatment combinations: burn only (B), thin only (T), burn and thin combined (BT), and a control (C). Burning and thinning treatments were administered in spring 2015. Changes in the FL estimates after the burn treatment revealed that the BT treatment combination consumed more fuel and burned more intensely compared to the B treatment. This observation was reflected in vegetation responses. The thinning reduced the canopy cover significantly, but under enhanced light environments, both oaks and competitive species thrived when no burn was incorporated. In contrast, burn treatments controlled the competitive vegetation. Hence, the most promising results were obtained when both fire and thinning were utilized. The remote sensing study documented the expansion of ERC in three areas of eastern Kansas over 30 years. The use of multi-seasonal layer-stacks with a Support Vector Machines (SVM) supervised classification was found to be the most effective approach to map ERC distribution. Total ERC cover increased by more than 6000 acres in all three study areas investigated in this study between 1986 and 2017. Much of the ERC expansion was into deciduous woodlands. Therefore, ERC control measures should be incorporated into oak woodland restoration efforts within the forest-prairie ecotone of Kansas.
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Harrell, Charles Wesley III. "Effects of prescribed burning, mechanical and chemical treatments to curtail rhododendron dominance and reduce wildfire fuel loads." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/31512.
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Rosebay rhododendron (Rhododendron maximum L.) is an ericaceous shrub commonly found in riparian areas of the Appalachian Mountains. After more than a century of fire exclusion in the U.S., the distribution of R. maximum and its dominance of forest understories have increased. Rhododendron expansion has caused a decline in overstory regeneration and the potential for dangerous fuel conditions around suburban structures near the wildland-urban interface. The purpose of this study was to determine the effects of seven silvicultural treatments on both the fuel loading within an R. maximum thicket and the control of R. maximum as a forest weed. The final objective of the project was to determine the cost effectiveness of each implemented treatment.
Due primarily to moisture conditions, a single prescribed burn was relatively ineffective in reducing fuel loading and causing R. maximum mortality. Mechanical cutting caused a drastic shift in the size-class distribution of R. maximum but resulted in heavy sprouting and increased fuel loading. Herbicide application did not reduce or increase fuel loading and was important in R. maximum control only when combined with other treatments. The prescribed burning treatment was the least expensive individual treatment while mechanical cutting was the most expensive. Combination treatments showed increased effectiveness in controlling R. maximum but were more expensive than the individual treatments. The results of the treatments from this study will be used over the long term to demonstrate to land managers the effects of vegetation control on rhododendron.Master of Science
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Pearce, Christopher Deane. "Effectiveness of Treatments to Reduce Rhododendron maximum and Promote Tree Seedling Regeneration in the Southern Appalachians." Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/41885.
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Rosebay rhododendron (Rhododendron maximum L.) is an evergreen ericaceous shrub that plays a dynamic role in the southern Appalachian forests. Commonly located on mesic sites, this understory shrub forms dense thickets that greatly reduce the amount of light available to herbaceous and woody plants found on the forest floor. Past research has shown that silvicultural methods can be used to eradicate R. maximum, however it is unclear which of these methods is most efficient and what effects other than stem mortality may occur. In this study, treatments involving prescribed fire, mechanical cutting, and herbicide applications were applied to R. maximum dominated forests in southwestern Virginia to determine what effect seven different silvicultural treatments had on 1) controlling of R. maximum as a forest weed 2) fuel loading inside of a R. maximum thicket, and 3) canopy tree seedling regeneration. Mechanical cutting treatments were successful in reducing R. maximum basal area per acre; however stump sprouting and increased fuel loading occurred. Herbicide applications were successful in controlling only the smallest diameter class of R. maximum stems. Prescribed fire reduced litter layers and caused delayed mortality on R. maximum stems three years following treatment. Hemispherical photographs taken within each plot showed that silvicultural treatments that successfully increased the amount of light entering each plot were influential in seedling establishment three years following treatments. Results from this study can be used to further perfect silvicultural applications that alleviate R. maximum cover on the forest landscape.Master of Science
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Tillová, Jana. "Studium chování betonů při působení vysokých teplot." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-225881.
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This master‘s thesis is focused on the study of the behavior of cement concrete at high temperatures with a focus on monitoring the impact of aggregate and cement type. This work describes the processes in aggregates and cement matrix at high temperatures. The theoretical part describes the selestion of a suitable aggregate and cement for the surroundings with potential exposure to high temperatures. In the experimental part is given design of composition of a concrete with two types of aggregates and four cements. It has been suggested 8 recipes. Changes were observed densities, compressive strength and tensile strength in bending, calculate the velocity of propagation of waves with ultrasonic pulsed method. Also evaluated the appearance of the surface samples after thermal load – cracks on the surface and measure the maximum crack width.
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Adamec, Tomáš. "Zvýšení životnosti zápalníku palné zbraně s pomocí explicitního řešiče." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443722.
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Firing pin is a critical component in terms of firearm function. Tip of firing pin can break off due to repeated impact loading, which results in malfunction of the whole firearm. This master's thesis aims to propose changes in geometry of the firing pin so that new firing pin will be more durable against fatigue failure. Geometry and characteristics of the original firing pin are provided by company Česká zbrojovka, a.s. To determine the amount of fatigue damage for specific configuration of firing pin, computational model, which simulates impact loading of the firing pin during dry fire, is created. Finite element method with explicit formulation is used for the calculation. Parameters of geometry, which are assumed to have highest influence on fatigue life, are chosen based on the analisys of the original firing pin. These parameters are changed in further calculations, resulting in new configuration of the firing pin, which is approximately 15 % more durable against fatigue failure.
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Žák, Michal. "Studium vlastností cementových betonů při působení vysokých teplot." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2016. http://www.nusl.cz/ntk/nusl-240106.
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This diploma thesis is focused on behavior of cement concrete at high temperatures. The theoretical part describes processes, which take place in concrete at thermal loading and effect of this thermal load to mechanical and physical properties of concrete. Also there was described recommendation for testing physical and mechanical of concrete at high temperatures according to RILEM TC. In experimental part mixes were made with greywacke aggregate, amphibolite aggregate and with the addition of polypropylene fibers or cellulose fibers. In these mixes was determined the effect of high temperatures on the density of concrete, compressive strength of concrete and thermal strain of concrete. Further there was tested addition of 2 kg/m3 polypropylene fibers to concrete with basalt aggregate and siliceous aggregate and influence of these fibers to density of concrete, compressive strength of concrete and dynamic modulus of elasticity.
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Magnusson, Mikael S. "Interfibre Joint Strength under Mixed Modes of Loading." Doctoral thesis, KTH, Hållfasthetslära (Inst.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-145669.
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The load carrying capacity of interbre joints are one of the key entities for build-up of strength inpaper materials. In order to gain insight in how to tailor the macroscopic properties of such materialsby chemical and/or mechanical treatments at a microscopic level, direct measurement of individualbre{bre crosses are typically performed. However, the state of loading in the interbre joint, intesting of individual bre{bre crosses, is in general very complex and an increased understandingfor how to evaluate the mechanical properties of interbre joints is desirable. In Paper A, amethod for manufacturing and measuring the strength of isolated interbre joints is presented. Themethod is applied to investigate the strength of bre{bre crosses at two dierent modes of loading.Also, an investigation on the manufacturing conditions is presented. The strength distribution ofindividually prepared bre{bre crosses is characterized and it was found that the median strengthin a peeling type of loading was about 20% compared to samples tested in the conventional shearingtype of loading. In Paper B, a procedure for evaluating interbre joint strength measurementsin terms of resultant forces and moments in the interbre joint region is presented. The methodis applied to investigate the state of loading in bre{bre crosses tested in peeling and shearing,respectively. It is shown that for a typical interbre joint strength test, the load components otherthan shear, cannot in general be neglected and is strongly dependent on the structural geometry ofthe bre{bre crosses. In Paper C, four distinctly dierent load cases; peeling, shearing, tearingand a biaxial type of loading was tested mechanically and evaluated numerically in order to gainmore information on how interbre joints behave in dierent modes of loading. In Paper D, thein uence of a chemical additive on the interbre joint strength is investigated on the microscopic(joint) scale and correlated to the eect previously observed on the macroscopic (sheet) scale. Xraymicrotomography and image analysis was used to understand structural changes in the brousnetwork in terms of the number of interbre joints as well as the average interbre joint contact area.The results showed that the median interbre joint strength increased by 18% upon adsorption, andthat the polyelectrolyte increased the number of contacts between the bres as well as an increasedarea of contact. In Paper E, the damage behaviour of individual interbre joints is analyzed. Froman extensive number of mechanical tests, the typical damage behaviour is identied and a failurecriterion is used to study the in uence of failure properties to give indications on how to tailor thematerial to optimize the joint strength.En av de viktigaste mekanismerna for den lastbarande formagan hos pappersmaterial ar brottegenskapernahos berfogarna. For att eektivt skraddarsy sadana materials egenskaper genom kemiskoch/eller mekanisk behandling samt for att forsta hur sadana modieringar paverkar egenskapernapa en mikroskopisk niva ar provning av individuella ber-ber-kors en allmant anvand metod. Belastningeni en berfog vid sadan provning ar dock generellt komplicerad och ytterligare kunskapom hur berfogars mekaniska egenskaper skall utvarderas ar onskvard. I Artikel A, presenterasen metod for tillverkning samt mekanisk provning av isolerade ber-kors vid tva olika typer avbelastning. Vidare undersoks hur torktrycket, torkmetoden samt graden av malning inverkar pafogstyrkan. Resultaten visar att brottlasten for en globalt akande belastning var omkring 20 % avbrottlasten for prov utforda med den konventionella skjuvande belastningen samt att styrkan hosindividuellt tillverkade berkors ar fordelade enligt en Weibull fordelning. I Artikel B, presenterasen numerisk metod for utvardering av fogstyrke-matningar med avseende pa kraft- och momentresultanternai gransytan mellan brerna. Metoden anvands for att studera belastningsmoden hosber-kors i tva principiellt olika lastfall. Resultaten visar att for ett typiskt berfogsprov, kan intelastkomponenterna, vid sidan av skjuvning, generellt forsummas da de ar starkt beroende avber-korsets geometri. I Artikel C, jamfors fogstyrkematningar under fyra principiellt olika lastfall; akande, skjuvande, rivande samt biaxiellt. De experimentella last-forskjutningskurvorna, samtde beraknade lastmoderna anvands for att undersoka vilket tillskott pa information de foreslagnalastfallen kan ge i hansyn till fogstyrkan hos massabrer. I Artikel D, undersoks en polymers (somabsorberats pa berytorna) inverkan pa saval berniva som pa natverksniva. Fiberfogstyrkan matsexperimentellt och eekten av den kemiska tillsatsen jamfors pa mikroskopisk niva (ber-kors) medtidigare uppmatt eekt pa makroskopisk niva (ark). Rontgentomogra och bildanalys anvands foratt undersoka de strukturella skillnaderna som uppstar i de brosa natverken vid absorption av enpolyamin och resultaten visar att antalet berfogar per berlangdenhet samt att medelkontaktareanokade. Resultaten visar ocksa att medianen av berfogsstyrkan okade med 18 %. Dessa eekter sammantagetar anledningen till varfor polyaminer, sasom PAH, ar sa eektiva for att oka torrstyrkanhos pappersmaterial. I Artikel E, karakteriseras skadebeteendet hos individuella berfogar franett omfattande antal matningar. Ett brottkriterium infors i den numeriska utvarderingsmetoden foratt studera skadebeteendet. Kanslighetsanalys och inverkan av brottparametrarna studeras ocksafor att ge indikationer pa hur egenskaperna kan skraddarsys for att optimera berfogstyrkan.
QC 20140527
BiMaC Innovation
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Shah, Syed Kamran Ayub. "Response of fibre metal laminates to blast loading." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/11188.
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Fibre-metal laminates (FMLs) are hybrid structures comprising interleaved metal sheets and fibre reinforced polymer composites. In this work the performance of fibre metal laminated plates under blast loading is studied numerically. The FML panels are made of alternating layers of aluminium and glass fibre/polypropylene (GFRP) with different number of layers of aluminium and composite and in the panels with equal number of layers, with different thicknesses of GFPP. The panels are subjected to global blast loading uniformly distributed over the surface of the panel and to local blast loading applied at the centre of the panel with a spatial exponential decay towards the edges. The displacements of the front and back faces are found to increase linearly with increasing impulse. The results for global blast loading are correlated with experimental results obtained by Langdon et.al [doi:10.1016/j.euromechsol.2007.09.003] and for localised blast loading with experimental studies conducted by Langdon et.al [doi:10.1016/j.ijimpeng.2006.05.008 , doi:10.1016/j.ijimpeng.2006.05.009]. A good correlation between the experimental and numerical results is found. Back face debonding is found in all the panels for both load cases. The results are also compared with the response of mild and armour steel plates having the same areal densities as FML panels. It has been shown that for the same impulse, the displacement of mild steel plate with the same areal density is approximately twice the back face displacement of FML for global blast and depends upon the thickness of mild steel plate. Therefore, for global blast loading FML performs better and can withstand higher impulses without rupture whereas mild steel plate tears apart for global blast loading and in certain cases for local blast loading. On the other hand, the displacements in armour steel are 70% to 80% of the corresponding FML panel with same areal density when subjected to global or local blast loading.
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Arora, Hari. "Blast loading of fibre reinforced polymer composite structures." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9625.
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The resistance of glass and carbon fibre reinforced polymer (GFRP and CFRP) sandwich panels and laminate tubes to blast in air and underwater environments have been studied. Explosive charges of 0.64-100 kg TNT equivalent were used during these studies. Procedures for monitoring the structural response of such materials during blast events have been devised. High-speed photography was employed during the air-blast loading of GFRP and CFRP sandwich panels, in conjunction with digital image correlation (DIC), to monitor the deformation of these structures under shock loading. Failure mechanisms have been revealed using DIC and confirmed in post-test sectioning. Strain gauges were used to monitor the structural response of similar sandwich materials and GFRP tubular laminates during underwater shocks. The effect of the supporting/backing medium (air or water) of the target facing the shock has been identified during these studies. Mechanisms of failure have been established such as core crushing, skin/core cracking, delamination and fibre breakage. Strain gauge data supported the mechanisms for such damage. A transition in behaviour was observed in the sandwich panels when subject to an underwater blast as opposed to an air-blast load. Damage mechanisms notably shifted from distributed core shear failure originating from regions of high shear in air blast to global core crushing in underwater blast. These studies were part of a research programme sponsored by the Office of Naval Research (ONR) investigating blast loading of composite naval structures. The full-scale experimental results presented in this thesis will aid and assist in the development of analytical and computational models. Furthermore, this work highlights the importance of support and boundary conditions with regards to blast resistant design. These outcomes were analysed further in finite element simulations of both air and underwater blast conditions, where boundary stiffness and support conditions were, as expected, shown to strongly influence structural response and deformation of the target.
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Loach, Simon C. "Repeated loading of fine grained soils for pavement design." Thesis, University of Nottingham, 1987. http://eprints.nottingham.ac.uk/13693/.
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The primary aim of this research was to investigate the behaviour of a clay subjected to a loading regime similar to that experienced by a road subgrade under traffic loading in Great Britain. The material used was Keuper Marl. The samples were anisotropically consolidated in a triaxial apparatus from a slurry which allowed careful control over the stress history and produced uniform samples. The samples were fully instrumented and the apparatus was capable of applying repeated axial and radial stresses. The test programme was designed to investigate the resilient and permanent response of the samples to a variety of stress pulse magnitudes and time periods. The main conclusions were: i) The material exhibited a marked stress softening. ii) The mean normal effective stress remained constant under a variety of total stress paths over the range of frequencies tested. iii) The resilient response was found to depend on the magnitude of the applied stress pulse and the mean normal effective pressure, and to be independent of the preconsolidation pressure. iv) The material exhibited significant thixotropy. A smaller parallel series of tests was carried out on compacted triaxial samples of three clays (Keuper Marl, Gault clay and London clay) in a simple pneumatic repeated load triaxial rig. The test programme was designed to investigate the resilient response of the samples over a range of repeated deviator stresses. The suction moisture content relationship for each clay was established, and the resilient response of the clay was found to be controlled by the magnitude of the stress pulse and the suction. A series of California Bearing Ratio tests was carried out on compacted samples of the three clays, and on anisotropically consolidated samples of Keuper Marl, to allow a comparison to be made between the resilient modulus and CBR. A review of previous work is presented.
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Syed, Mohsin Sharifah Maszura Binti. "Behaviour of fibre-reinforced concrete structures under seismic loading." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/17804.
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The present research is concerned with the modelling of the structural behaviour of steel fibre-reinforced concrete (SFRC) using non-linear finite-element (FE) analysis. Key structural response indicators such as load-deflection curves, strength, stiffness, ductility, energy absorption and cracking were examined. In particular, the potential for fibres to substitute for a reduction in conventional transverse reinforcement was studied. Such reduction is highly desirables in practice as it helps alleviate reinforcement congestion, often experienced in the seismic detailing of critical regions such as beam-column joints. Thus two key parameters were considered, namely reducing transverse reinforcement while increasing the amount of fibres. The reduction in conventional reinforcement was achieved mainly by increasing stirrups spacing (and also by reducing double-hoop arrangement commonly used in seismic detailing of joints). The behaviour of SFRC structural elements was studied under both monotonic and reversed-cyclic loadings (the latter used to mimic seismic action). Emphasis was initially focused on the study of available experimental data describing the effect of steel fibres on the post-cracking response of concrete. Consequently the SFRC constitutive model proposed by Lok and Xiao (1999) was selected. The numerical model was calibrated against existing experimental data to ensure the reliability of the FE predictions. Subsequently, further analyses were carried out investigating three main case studies namely, simply supported beams, two-span continuous (i.e. statically-indeterminate) columns, and both exterior and interior beam-column joints. Parametric studies were carried out covering the full practical range of steel fibre dosages and appropriate amounts of reduction in conventional transverse reinforcement. The results show that steel fibres increase the load-carrying capacity and stiffness (thus enhancing response at both the serviceability and ultimate limit states, which are important design considerations). Fibres were found also to improve ductility (as well as altering the mode of failure from a brittle to a ductile one).
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Zamperini, Silvia. "Effects of cyclic loading on fibre reinforced titanium metal matrix composites." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289709.
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Ghoor, Ismail B. "The response of concave singly curved fibre reinforced moulded sandwich and laminated composite panels to blast loading." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/27811.
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Composite materials are increasingly being used in a wide range of structural applications. These applications range from bicycle frames and building facades to hulls of marine ships. Their popularity is due to the high specific strength and stiffness properties, corrosion resistance, and the ability to tailor their properties to a required application. With the increasing use of composites, there is a need to better understand the material and damage behaviour of these structures. In recent years, the increased frequency of wars and terror attacks have prompted investigations into composite failure processes resulting from air-blast. Most of the research has been focused on flat panels, whereas there is relatively little on curved structures. This dissertation reports on the effect of air-blast loading on concave, singly curved fibre reinforced sandwich and composite panels. Sandwich panels and equivalent mass glass fibre laminates were manufactured and tested. Three types of curvature namely a flat panel (with infinite curvature), a curvature of 1000 mm radius and a curvature of 500 mm radius were produced, to determine the influence of curvature on panel response. The laminates were made from 16 layers of 400 g/m² plain weave glass fibre infused with Prime 20 LV epoxy resin. The sandwich panels consisted of a 15 mm thick Airex C70:75 core sandwiched between the 12 layers of 400 g/m² plain weave glass fibre and infused with Prime 20 LV epoxy resin. This arrangement produced a balanced sandwich panel with 6 layers of glass fibre on the front and back respectively. For all panels, vacuum infusion was used to manufacture in a single shot process. Mechanical properties of samples were tested for consistency in manufacturing. It was found that mechanical properties of the samples tested were consistent with low standard deviations on tensile and flexural strength. The panels were tested in the blast chamber flat the University of Cape Town. Blast specimens were clamped onto a pendulum to facilitate impulse measurement. Discs of plastic explosive, with charge masses ranging from 10 g to 25 g, were detonated. After blast testing, a post-mortem analysis of the damaged panels was conducted. Post-mortem analysis revealed that the failure progression was the same irrespective of curvature for both the sandwich panels and the laminates. Sandwich panels exhibited the following failure progression: delamination, matrix failure, core crushing, core shear, core fragmentation, core penetration and fibre fracture. The laminates displayed the following progression: delamination, matrix failure and fibre fracture. Curved panels exhibited failure initiation at lower charge masses than the flat panels. As the curvature increased, the failure modes initiated at lower charge masses. For example, as the charge mass was increased to 12.5 g the front face sheets of the flat and the 1000 mm radius sandwich panels exhibited fibre fracture, but the 500 mm radius sandwich panel exhibited fibre fracture and rupture through the thickness of the front face sheet. The 500 mm radius laminate exhibited front face failure earlier (15 g) than the 1000 mm radius (22.5 g) and flat panel (20 g). Curved laminates exhibited a favoured delamination pattern along the curved edges of the panel for both 1000 mm and 500 mm radii laminates. As the curvature increased, more delamination was evident on the curved edges. The curved panels displayed more severe damage than flat panels at identical charge masses. Curved sandwich panels experienced through thickness rupture at 20 g charge mass whereas the curved laminates did not exhibit rupture at 25 g charge mass. The flat laminates were the most blast resistant, showing no through-thickness penetration at 25 g (the highest charge mass tested) and initiated failure modes at higher charge masses when compared to the other configurations.
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Leong, Kok Hoong. "Damage accumulation in cross-ply polymer matrix composite laminates under mechanical loading." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241115.
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Guerrero, Garcia José Manuel. "Micromechanical modelling of hybrid unidirectional composite materials under fibre tensile loading." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/669043.
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In this thesis, a micromechanical model for predicting the tensile failure process in hybrid and non-hybrid unidirectional composite materials under fibre tensile loading is developed. Derived from this, the influence that different parameters have on the failure development in hybrid composites is investigated. The results prove that the model captures qualitatively well the failure development of composite materials. Moreover, adding matrix yielding and dynamic effects into the model allows to improve the modelling predictions compared with experimental results. It is also proved that the size of the material has a significant influence on the hybrid properties, and the dispersion of the fibres in the hybrid material has a large importance on the failure and damage development. Therefore, this thesis gives a step forward towards the inclusion of hybrid composites into commercial design and the generation of more optimised materialsEn aquesta tesi, es desenvolupa un model micromecànic per predir el procés de ruptura a tracció de materials compostos unidireccionals híbrids i no híbrids sotmesos a càrregues longitudinals. Derivat d’això, la influència que diferents paràmetres tenen, en el procés de ruptura de materials híbrids, és investigada. Els resultats demostren que el model captura qualitativament el procés de trencament en materials compostos. A més, afegir plasticitat a la matriu i efectes dinàmics en el model permet millorar les prediccions del model comparat amb resultats experimentals. També es demostra que la mida del material té una influència significativa en les propietats híbrides, i que la dispersió de les fibres en el material híbrid té una gran importància en el trencament i el desenvolupament de dany. Per tant, aquesta tesi dóna un pas endavant cap a la inclusió de compostos híbrids en el disseny comercial i la generació de materials més optimitzats
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Seidalinova, Ainur. "Monotonic and cyclic shear loading response of fine-grained gold tailings." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46531.
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The monotonic, cyclic and post-cyclic shear response of gold tailings was investigated using constant-volume direct simple shear test device. The reconstituted gold tailings specimens normally consolidated to vertical effective stress levels ranging from 50 kPa to 400 kPa initially exhibited contractive behaviour followed by a dilative response under monotonic loading, with their shear stiffness and strength increasing with increasing initial effective confining stress. Overconsolidated specimens developed negative excess pore pressures during monotonic shear, with increasing dilative response, shear resistance, and stiffness displayed with increasing overconsolidation ratio (OCR). Overall, the monotonic behaviour of normally consolidated reconstituted gold tailings specimens is similar to the typical monotonic behaviour of normally consolidated clays and low-plastic silts; similarly, the behaviour of overconsolidated reconstituted gold tailings specimens is similar to the typical monotonic behaviour of overconsolidated clays. During cyclic loading, the tailings exhibited cumulative decrease in effective stress (or increase in equivalent excess pore-water pressure) with increasing number of loading cycles, resulting in progressive degradation of shear stiffness. The cyclic shear resistance increased with increasing OCR. The findings on the cyclic shear response of normally consolidated reconstituted gold tailings are in general agreement with those available published data on the cyclic response of different tailings, obtained from tests carried out on cyclic triaxial (TX) and DSS devices. The CRR of the gold tailings from this study, however, was found to be higher than that observed in Fraser river sand and Quartz rock powder, but in the same range as natural Fraser river silt. The post-cyclic monotonic shearing response, obtained from DSS tests, carried out on normally consolidated and overconsolidated reconstituted gold tailings specimens was also studied as a part of the current research work. The post-cyclic shear strength of normally and overconsolidated specimens, normalized to the initial effective confining stress, were observed to increase with increasing OCR. The post-cyclic consolidation volume changes experienced by the gold tailings specimens were in agreement with previously published results suggesting that post-cyclic volumetric strains would increase with increasing maximum excess pore water pressure ratio developed during cyclic loading.
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Mohammadi, Hosinieh Milad. "Behaviour of High Performance Fibre Reinforced Concrete Columns under Axial Loading." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30726.
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When compared to traditional concrete, steel fibre reinforced concrete (SFRC) shows several enhancements in performance, including improved tensile resistance, toughness and ductility. One potential application for SFRC is in columns where the provision of steel fibres can improve performance under axial and lateral loads. The use of SFRC can also allow for partial replacement of transverse reinforcement required by modern seismic codes. To improve workability, self-consolidating concrete (SCC) can be combined with steel fibres, leading to highly workable SFRC suitable for structural applications. Recent advances in material science have also led to the development of ultra-high performance fibre reinforced concretes (UHPFRC), a material which exhibits very high compressive strength, enhanced post-cracking resistance and high damage tolerance. In heavily loaded ground-story columns, the use of UHPFRC can allow for reduced column sections.
This thesis presents the results from a comprehensive research program conducted to study the axial behaviour of columns constructed with highly workable SFRC and UHPFRC. As part of the experimental program, twenty-three full-scale columns were tested under pure axial compressive loading. In the case of the SFRC columns, columns having rectangular section and constructed with SCC and steel fibres were tested, with variables including fibre content and spacing of transverse reinforcement. The results confirm that use of fibres results in improved column behaviour due to enhancements in core confinement and cover behaviour. Furthermore, the results demonstrate that the provision of steel fibres in columns can allow for partial replacement of transverse reinforcement required by modern codes. The analytical investigation indicates that confinement models proposed by other researchers for traditional RC and SFRC can predict the response of columns constructed with SCC and highly workable SFRC. In the case of the UHPFRC columns, variables included configuration and spacing of transverse reinforcement. The results demonstrate that the use of appropriate detailing in UHPFRC columns can result in suitable ductility. Furthermore, the results demonstrate the improved damage tolerance of UHPFRC when compared to traditional high-strength concrete. The analytical investigation demonstrates the need for development of confinement models specific for UHPFRC.
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Magnusson, Mikael S. "Testing and Evaluation of Interfibre Joint Strength under Mixed-Mode Loading." Licentiate thesis, KTH, Hållfasthetslära (Inst.), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116700.
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The failure properties of interfibre bonds are the key for the build-up of strength in fibrous materials such as paper and paperboard. In order to tailor the properties of such materials by chemical or mechanical treatments and to learn how such modifications influence the properties at a microscopic level, direct measurement of individual fibre--fibre crosses are typically performed. However, the state of loading in the interfibre joint, in testing of individual fibre--fibre crosses, is in general very complex and a greater understanding for how to evaluate the mechanical properties of interfibre joints is desirable. In Paper A, a method for manufacturing multiple fibre--fibre cross specimens and a procedure for testing interfibre joints at different modes of loading is presented. The method is applied to investigate the strength of fibre-fibre crosses with different geometry and at two principally different modes of loading. Also, an investigation on the influence of drying pressure, the drying method as well as a comparison of pulp fibres from two different degrees of refining is presented. The force at rupture is scaled in terms of different geometric parameters; nominal overlap area, length and width of the joint region. It is shown that neither of the methods of scaling unambiguously reduced the coefficient of variation of the mean strength and that the force at rupture in a peeling type of loading was about 20% of the ones tested in the conventional shearing type of loading. In Paper B, a procedure for evaluating interfibre joint strength measurements in terms of resultant forces and moments at rupture is presented. The method is applied to investigate the state of loading in fibre-fibre crosses tested in two principally different modes of loading. It is shown that for a typical interfibre joint test, the modes of loading other than pure shear, cannot in general be neglected and is strongly dependent on the structural geometry of the fibre-fibre crosses. Also, the stress state in the interface centroid was estimated in order to quantify how the mode of loading influence the amount of normal stresses that develop in relation to the amount of shear stresses in the interfibre joint.De brottmekaniska egenskaperna hos fiberfogar är nyckeln för uppbyggnaden av styrka hos fibrösa material såsom papper och kartong. För att effektivt skräddarsy sådana materials egenskaper genom kemisk eller mekanisk behandling och för att förstå hur sådana modifieringar påverkar egenskaperna på en mikroskopisk nivå är provning av individuella fiber-fiber-kors en allmänt använd metod. Belastningen i en fiberfog vid provning av individuella fiber-fiber kors är dock generellt mycket komplicerad och ytterligare kunskap om hur fiberfogars mekaniska egenskaper skall utvärderas är önskvärd. I Artikel A, presenteras en metod för samtidig tillverkning av flera fiber-fiber kors samt en metod för mekanisk provning av dessa med olika typer av belastning. Metoden tillämpades för att studera styrkan av fiber-fiber-kors med olika geometri och vid två olika lastfall. En undersökning av hur torktrycket, torkmetoden samt graden av malning inverkar på fogstyrkan presenteras. De uppmätta brottlasterna skalades med olika karakteristiska längder för fogen; nominell överlapparea samt fogens längd och bredd. Resultaten visade att ingendera av normaliseringsmetoderna reducerade variationskoefficienten (av medelvärdet av styrkan) samt att brottlasten för en globalt fläkande belastning var omkring 20 % av brottlasten för prov utförda med den konventionella skjuvande belastningen. I Artikel B, presenteras en metod för utvärdering av mätningar av styrkan hos fiberfogar med hänseende på kraft- och moment- resultanterna i gränsytan mellan fibrerna. Metoden används för att studera belastningsmoden hos fiber-fiber--kors provade i två principiellt olika lastfall. Resultaten visar att för ett typiskt fiberfogsprov av isolerade fiber-fiber-kors med långa fria fibersegment, så kan inte belastningsmoderna vid sidan av skjuvning försummas och att de är starkt beroende av fiber-fiber-korsets geometri. För att kunna jämföra fiberfogar av olika storlek och kvantifiera förhållandet mellan normal- och skjuvbelastningen i fogen skalades de resulterande krafterna och momenten med tvärsnittsstorheter baserade på en approximation av fogareans utformning.
QC 20130125
BiMaC Innovation
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Kolle, Boris. "Behaviour of steel fibre reinforced high performance concrete under biaxial loading conditions." Thesis, University of Glasgow, 2006. http://theses.gla.ac.uk/715/.
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This thesis includes an experimental investigation of the behaviour of steel fibre reinforced high performance concrete (SFRHPC) under biaxial loading conditions. Also included are constitutive models to enable numerical predictions of the strength behaviour of such a material. Within the experimental stage a large biaxial test machine was designed and manufactured. The load capacity of each axis was 2000 kN. Special thought was given to the load platen system because of the friction which occurs between the platen system and the concrete specimen. Brush bearing platens and solid steel blocks with and without Teflon friction reducing pads were tried. Because the brush platen and the Teflon pads were constantly damaged during testing, solid steel block platens were finally used. For tests where tension loads were involved, experiments were carried out with dog-bone shaped specimens and specimens glued on to the platens. Finally, the tension loads were transferred through threaded rods cast into the specimens and connected to the machine patterns with screws. Modern control schemes and high speed data acquisition systems were used to monitor the material response and to collect experimental stress and strain results. The principal deformations were monitored and the crack patterns and failure modes examined. Failure envelopes were developed based on the strength data for each fibre variable. The load capacity of SFRHPC under biaxial load conditions was found to be larger than for plain HPC for all fibre types and volume fractions. The stress-strain recordings indicated a linear behaviour almost up to failure. The examined failure mode between plain and steel fibre HPC was similar and all specimens failed very suddenly with a splitting failure type. The test variables included four different types of hooked ended steel fibres with different fibre volume fractions from plain to 2% in 0.5% steps. The specimens were tested under the entire range of stress combinations including uniaxial compression and tension and biaxial compression-compression and compression-tension. As a result the specimen still failed in an explosive manner but the pieces were still connected together by fibres after failure. The biaxial strength compared to the uniaxial strength increased more, as observed with normal strength concrete. With the addition of fibres the biaxial strength behaviour of HPC was almost the same as for plain normal strength concrete. The deformation characteristics of plain and SFRHPC showed a linear behaviour up to a higher stress than normal strength concrete. In fact the linear limit was almost as high as the failure load. The examined strength data was used to model the biaxial strength envelopes of HPC and SFRHPC using different methods. These included the Ottosen failure criterion and the Willam and Warnke failure criterion.
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Volschenk, Gideon. "The response of aluminium and glass fibre FMLS subjected to blast loading." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/13755.
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Fibre-Metal Laminates (FMLs) have long been of interest to the aeronautics industry due to their exceptional strength to weight ratio, fatigue and impact resistance. Due to the increasing global risk of subversive activity in this industry, the focus of research in recent years has shifted to the blast resistance of these materials. A particularly interesting material being GLARE, a commercially available Aluminium-GFRP FML. This dissertation presents the results of an experimental study into the effects of glass fibre configuration and epoxy type on the response of glass fibre reinforced, epoxy-based FMLs, subjected to localised and uniform blast loading conditions. Standard tensile specimens and Single-Leg Bend (SLB) specimens were manufactured and tested to determine the properties constitutive materials and interfacial bond strength. Bond strength between the composite and metal interfaces was improved by employing a combination of surface treatments, consisting of both mechanical and chemical as well as the use of a film adhesive. FMLs were manufactured from Al 2024-T3 and e-glass fibre reinforced epoxy composite. Both woven and unidirectional fibre configurations were used as part of either a prepreg or wet layup to construct the composite layers. Tensile and SLB specimens were used to characterise the constitutive materials and interfacial bond strength. SLB tests were used to determine the effect of cure cycle and composite layup technique on interfacial bond strength. These tests and revealed a variety of interfacial failure modes for different cure cycles and epoxy configurations, each resulting in different levels of strength. The modes, in increasing order of strength, included debonding of the film adhesive from either the metal or composite interface or both, and in some cases also included delamination in the composite layer. Tests showed that a single stage layup and cure cycle resulted in the strongest bonds between interfaces, compared to a multi-stage manufacturing processes. It was also shown that the use of prepreg resulted in stronger inter-facial bonds than a wet-layup process. The properties of the constitutive materials were used to construct a numerical model to aid in experimental design. The model was used to determine a suitable range of charge masses for testing.
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Kölle, Boris. "Behaviour of steel fibre reinforced high performance concrete under biaxial loading conditions." Connect to e-thesis, 2006. http://theses.gla.ac.uk/715/.
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Thesis (Ph.D.) - University of Glasgow, 2006.Ph.D. thesis submitted to the Department of Civil Engineering, University of Glasgow, 2006. Includes bibliographical references. Print version also available.
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Mohamed, Galal F. A. "Modelling damage and fracture of fibre metal laminates subject to blast loading." Thesis, University of Sheffield, 2012. http://etheses.whiterose.ac.uk/2114/.
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The present thesis investigates the performance of current aerospace structural materials such as Glare, a fibre metal laminate, to the catastrophic consequence of sabotage-induced blast loadings on commercial aircraft. The aim is to quantify the effects of these blast events and establish if remedial action can in some manner increase the chances of aircraft survivability. Within the EU funded VULCAN consortium, a coordinated effort has been devised to determine the dynamic deformation and fracture behaviour of structural materials subject to blast loadings using both experimental and numerical techniques. Test data from small-scale experimental blast trials have been verified and validated by the author using robust and efficient finite element models. Numerical studies have shown that Glare has potential to be a strong candidate for blast attenuating structures, exhibiting superior blast resistance compared to monolithic aluminium plates. Furthermore, a blast vulnerability and survivability analysis was devised to illustrate various failure scenarios in scaled fuselage structures. To address the macroscopic crack propagation in large-scale shell structures to blast loadings, well-controlled dynamic fracture experiments have been performed. This configuration, which consists of closed-end pressurised barrels with a through-thickness crack, is designed to capture the underlying dynamic phenomena under investigation whilst keeping the computational effort manageable. Quantitative fracture metrics obtained from high speed imaging systems have shown that Glare exhibits much lower average crack velocities than Aluminium 2024-T3 and CFRP. Experimental boundary and loading conditions served as well-defined input parameters to large-scale finite element models using cohesive elements. It has been shown that rate-independent cohesive models, initially verified using quasi-static fracture toughness tests, are insufficient to capture the dynamic crack growth rates. Alterative rate-dependent models have been discussed and implemented which take into account the influence of loading rate on the cohesive traction and energy dissipation. An inverse problem of cohesive zone modelling is performed to obtain mode-I cohesive zone laws. The comparison shows that both the experiments and the numerical simulations result in very similar crack initiation times and produce crack tip velocities of acceptable agreement.
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Pinheiro, Fabiola M. R. "Effects of forest fires and clear-cutting on mercury loading to boreal lakes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0034/MQ64431.pdf.
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Jradi, Layal. "Study of the influence of fine particles on the properties of liquefaction of sands." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1053/document.
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Au cours des 50 dernières années, l’étude du phénomène de liquéfaction de sols sableux saturés ont fait l'objet de nombreuses recherches en laboratoire. La plupart de ces recherches antérieures se sont concentrées sur la liquéfaction de sables propres, en supposant que la présence de fines limite le développement de la surpression interstitielle et donc le risque de liquéfaction. Cependant, les sables sableux naturels se trouvent généralement dans la nature sous la forme d'un mélange de sable et de fines et, l’influence de ces fines sur le risque de liquéfaction de ce type de matériau n'est toujours pas claire. En effet, on trouve des résultats contradictoires, dans la littérature, sur l'effet des particules fines sur le phénomène de liquéfaction des sables. Dans ce contexte, l’objectif principal de ce travail expérimental est de clarifier et de quantifier l’influence des particules fines présentes au sein d’une matrice sableuse sur l’initiation et le développement du phénomène de liquéfaction. On s’est intéressé, en particulier, à la nature des particules fines (plastique/non-plastique), à leur proportion au sein de la matrice, à l’état de compacité de la matrice et à l’état de contrainte initial (état de consolidation). A cet effet, à l'aide d'un nouveau dispositif triaxial servo-hydraulique, une série d'essais monotones et cycliques ont été effectués afin de clarifier cet effet. Les résultats expérimentaux montrent que l'augmentation de la proportion de fines non plastiques augmente la résistance à la liquéfaction du mélange sous chargements monotone et cyclique. Par contre, cette tendance est inversée pour les mélanges qui contiennent des fines plastiques. Enfin, une comparaison a été établie entre le comportement de ces sols sous cisaillement monotone et cyclique non drainé en termes d'évaluation du déclenchement du phénomène d'instabilité et d'autres paramètres mécaniquesSince the last 50 years, the study of the phenomenon of liquefaction of saturated sandy soils has been a topic of extensive laboratory research. Most of the earlier research has focused on the liquefaction of clean sands assuming that the presence of fines resists the development of pore water pressure as well as the risk of liquefaction. However, natural sand is found in nature under the form of a mixture of sand and fines and, the influence of these fines on the liquefaction risk of this type of material is still unclear. In fact, we could find contradictory results in the literature review of the effect of fine particles on the sand liquefaction phenomenon. In this context, the main objective of this study is to clarify and quantify the influence of fine particles (plastic and non-plastic) present in a sandy matrix on the initiation and development of the liquefaction phenomenon .We’ve focused, in particular, on the nature of fine particles (plastic/non-plastic), their proportion in the matrix, the matrix compactness condition and initial stress state (state consolidation). For this purpose, with the aid of a new triaxial servo-hydraulic device, a series of monotonic and cyclic tests were done in order to clarify this effect. Experimental results show that the increase in non-plastic fines increases the resistance to liquefaction of the mixture under both monotonic and cyclic loading. However, this trend is reversed for the mixtures containing plastic fines. Finally a comparison has been established between the behavior of these soils under undrained monotonic and cyclic shearing in terms of evaluation of the initiation of instability phenomenon and other mechanical parameters
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Teo, Wern Sze. "The performance of carbon-fibre composite joints : pre-bond moisture and loading rate effects." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501293.
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Burrell, Russell P. "Performance of Steel Fibre Reinforced Concrete Columns under Shock Tube Induced Shock Wave Loading." Thesis, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23516.
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It is important to ensure that vulnerable structures (federal and provincial offices, military structures, embassies, etc) are blast resistant to safeguard life and critical infrastructure. In the wake of recent malicious attacks and accidental explosions, it is becoming increasingly important to ensure that columns in structures are properly detailed to provide the ductility and continuity necessary to prevent progressive collapse. Research has shown that steel fibre reinforced concrete (SFRC) can enhance many of the properties of concrete, including improved post-cracking tensile capacity, enhanced shear resistance, and increased ductility. The enhanced properties of SFRC make it an ideal candidate for use in the blast resistant design of structures. There is limited research on the behaviour of SFRC under high strain rates, including impact and blast loading, and some of this data is conflicting, with some researchers showing that the additional ductility normally evident in SFRC is absent or reduced at high strain loading. On the other hand, other data indicates that SFRC can improve toughness and energy-absorption capacity under extreme loading conditions. This thesis presents the results of experimental research involving tests of scaled reinforced concrete columns exposed to shock wave induced impulsive loads using the University of Ottawa Shock Tube.
A total of 13 half-scale steel fibre reinforced concrete columns, 8 with normal strength steel fibre reinforced concrete (SFRC) and 5 with an ultra high performance fibre reinforced concrete (UHPFRC), were constructed and tested under simulated blast pressures. The columns were designed according to CSA A23.3 standards for both seismic and non-seismic regions, using various fibre amounts and types. Each column was exposed to similar shock wave loads in order to provide direct comparisons between seismic and non-seismically detailed columns, amount of steel fibres, type of steel fibres, and type of concrete.
The dynamic response of the columns tested in the experimental program is predicted by generating dynamic load-deformation resistance functions for SFRC and UHPFRC columns and using single degree of freedom dynamic analysis software, RCBlast. The analytical results are compared to experimental data, and shown to accurately predict the maximum mid-span displacements of the fibre reinforced concrete columns under shock wave loading.
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Krashanitsa, Roman Yurievich. "An Inverse Computational Approach for the Identification of the Parameters of the Constitutive Model for Damaged Ceramics Subjected to Impact Loading." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1390%5F1%5Fm.pdf&type=application/pdf.
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Stuhlinger, Martin Ernst. "The influence of mixing ratio on the fatigue behaviour of fibre reinforced polymers." University of the Western Cape, 2013. http://hdl.handle.net/11394/5041.
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Magister Scientiae Dentium - MSc(Dent)Statement of the problem: Fibre reinforcement of polymethyl methacrylate (PMMA) denture base material is known to improve the strength, as well as the fatigue behavior, of the material. The powder liquid (P/L) ratio of PMMA is often changed to modify the handling properties of the material. Little is known about the effect of this deviation from manufacturer’s guidelines on the fatigue behaviour of the fibre reinforced product. Purpose: This study compared the flexural strength (FS) of PMMA reinforced with glass fibre using different P/L ratios, before and after cyclic loading. Methods and materials: Three groups, with 50 glass fibre reinforced (everStick nonimpregnated fibers) heat-cured PMMA resin (Vertex Rapid Simplified) specimens each, were prepared using a custom-made template (dimensions 10x9x50mm). Each group had a different P/L ratio: the control group (100%) had the manufacturer’s recommended ratio; the 90% and 80% groups had reduced P/L ratios (by weight).Twenty five specimens from each group were subjected to a 3-point bending compression test using a universal testing machine. The remaining 25 specimens from each group were subjected to cyclic loading (104 cycles) before compression testing. The (FS) was calculated using the highest force (Fmax) before specimen failure. Flexural strength was calculated using the equation: FS=3WL/2bd2. Within each group, median FS values before and after cyclic loading were compared by means of a non-parametric analysis of variance. The Aligned Ranks Transform method was used for the analysis. Statistical significance was set at p=0.05. Results: The Fmax (N) of the control (100%), 90% and 80% groups fatigued and unfatigued were 100%: 1665 (fat), 1465 (unfat); 90%: 1679 (fat), 1548 (unfat) and 80%: 1585 (fat), 1467 (unfit) respectively. There was no significant interaction between Mix ratio and Fatigue state, and the 80% mix had a significantly higher mean than either the 90% or 100% mix (with differences of about 0.3 units for both). The Fatigued state had a higher mean than the Un- fatigued state by about 6.0 units. Using FS (MPa) it was found that the fatigued 80% mix specimens had the highest value. The FS MPa of the control (100%), 90% and 80% groups fatigued and un-fatigued were 64.3, 60.6; 66.9, 65.6 and 70.2, 69.3 respectively. The fact that fatiguing strengthened the specimens merits further research. When observing the broken specimens it was found that there was a complete debonding of the fibres and the PMMA. Conclusion and clinical relevance: a) Fibre: The benefit of using glass fibre bundles to reinforce prostheses fabricated using heat cured PMMA is questionable due to problems with bonding between the fibre bundles and the heat cured PMMA resin. b) Fatiguing: An average person chews 107 times during a 3 year period. A limited period of average masticatory forces should not have a detrimental effect on prostheses made from heat cured PMMA resin. c) Mix ratio: Within the normal parameters of laboratory techniques the mix ratio of PMMA resin had no significance on the fracture resistance of the prostheses. Due to the high cost of the fibres used for the reinforcement and the limited success and insignificant results achieved in this study, this researcher cannot recommend using Stickbond or Stick fibers for the reinforcement of dentures made with heat cured PMMA resin.
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Schreiber, Sascha K. "Punching shear capacity of slab-column connections with steel-fibre reinforcement under lateral cyclic loading." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ60493.pdf.
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Bateman, Samuel. "Hollow core fibre-based gas discharge laser systems and deuterium loading of photonic crystal fibres." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648951.
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Research towards the development of a gas-discharge fibre laser using noble gases, with target emission wavelengths in the mid-IR. Additional and separate work on gas treatment methods for managing the formation of photo-induced defects in silica glass.
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Do, Tan Manh. "Excess pore water pressure generation in fine granular materials under cyclic loading -A laboratory study." Licentiate thesis, Luleå tekniska universitet, Geoteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-83517.
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Khusru, Shovona. "High performance hybrid structural column with rubberised concrete under axial compressive loading." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/233665/1/Shovona_Khusru_Thesis.pdf.
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Every year millions of tyres are disposed of worldwide in landfill resulting in the rise of an environmental burden. This thesis demonstrates the development of a sustainable novel hybrid double skin tubular column utilizing the scrap tyre rubbers. The proposed column made with rubberised concrete infill, filament wound FRP outer tube and steel inner tube, has been studied extensively through experimental testing, finite element modelling and parametric studies, to understand the structural performance under axial loading. This column, compared to the traditional column will be sustainable and beneficial at the locations demanding improved ductility, energy absorption and corrosion resistance.
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Khalighi, Yashar. "A study of bond between fibre reinforced polymer and concrete under quasi static and impact loading." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12345.
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This thesis examines the typical behavior of the interface bond between a selection of FRP treatments and various types of surface preparation on reinforced concrete beams under loading. It also describes an innovative specimen that enables examination of bond properties using a notched beam under a four-point bending test. The thesis also studies the bond between FRP and concrete under impact loading and discusses the strain rate sensitivity of the FRP–concrete bond.
Three surface treatment methods (water jetting, sandblasting, and jackhammering), two bonding agents (aromatic isocyanate (ATPRIME®) and vinyl ester), and three FRP systems (sprayed glass fiber reinforced polymer, sprayed carbon fiber reinforced polymer, and glass fiber reinforced polymer wrap) were investigated. The influences of FRP bond length, specimen notch depth, and a wide range of loading rates (creep, quasi-static loading, and impact loading) on bond behavior were also investigated. The notched beam specimen was also used to understand the debonding mechanism under impact loading. An impact setup was successfully developed to measure the bond stress and fracture energy of the FRP–concrete bond.
Bond strength values and toughness values were calculated for different surface treatments, FRP application methods, and bonding agents used. The FRP–concrete bond strength was found to be a strain rate sensitive parameter that increases as the strain rate increases. A dynamic improvement factor (DIF) was defined to characterise the influence of different material and strain rate parameters on bond strength. A correlation was found to relate dynamic improvement factor to strain rate for different surface preparation types.
An attempt was made to calibrate the energy and traction parameters of the cohesive element in ABAQUS to reproduce the same load displacement behavior as observed in the test from a modeled beam. Using different ABAQUS cohesive zone parameters, the load displacement behavior of the beam was modeled. Even though the load displacement did not completely match the tests, similar magnitudes of displacement and stress were achieved and the debonding mechanism was similar to the reality.