Nos projetos hidráulicos de irrigação são contabilizadas as perdas de carga totais, que seriam as perdas contínuas ou principais e as localizadas, objetivando maximizar a uniformidade de distribuição de água, caracterizando um conjunto motobomba adequado ao sistema de irrigação e com isso, minimizando os custos anuais e de implantação do projeto. Com o uso da informática, problemas de cálculos complexos são resolvidos com muita facilidade; desta forma pode-se aplicar modelos mais complexo para calculo da perda de carga nos sistemas de irrigação, resultando em valores mais próximos da realidade, com maiores riquezas de detalhes. A perda de carga representa a dissipação de energia da água em forma de calor, ao longo da tubulação, decorrente da resistência ao escoamento oferecida pela viscosidade do fluido e pela inércia das partículas. É variável de acordo com o tamanho das rugosidades da parede do tubo, diâmetro da tubulação e com a velocidade da água. A indústria de plásticos e seus derivados, com o auxilio da engenharia, tem aprimorado a qualidade dos materiais destinados à fabricação dos tubos, principalmente de polietileno. A utilização de tubos fabricados de matérias plásticos, de menor custo, destinados à irrigação tem aumentado nos últimos anos. A flexibilidade desses tubos traz como consequência o aumento do diâmetro interno com o aumento da pressão, fato este já observado em pesquisa e que não são levados em consideração pelos equacionamentos matemáticos utilizados para determinação da perda de carga. O presente trabalho propõe um modelo onde leva em consideração o módulo de elasticidade (E) do tubo para determinar a alteração do diâmetro em tubos elásticos provocada pela pressão, afetando assim a determinação da perda de carga contínua. Conhecer detalhadamente a causa da perda de energia, com intuito de cada vez mais otimizar a energia gasta por área irrigada no cenário brasileiro, passa a ser de fundamental importância. O Modelo Elástico proposto associado à Equação Universal, apresentou índice de desempenho médio de 0,9 sendo considerado com uma estimativa muito boa da realidade. / Total head losses are accounted in the irrigation hydraulic projects, that would be the continuous losses and the local head losses, aiming to maximize the uniformity of water distribution, characterizing an adequate pump set to the irrigation system e thus, minimizing the project implantation and annual costs. With informatics support, complex calculation problems are solved with ease, therefore it is possible to apply more complex models for head loss calculation in the irrigation system, resulting in values closer to the reality, with greater details. The head loss represents the water energy dissipation as heat, along the piping, due to the resistance to the flow offered by the fluid viscosity and by the particles inertia. It is variable according to the size of the rugosities of the pipe wall, piping diameter and the water velocity. plastic industry and its derivates, with engineering support, have improved the quality of the materials for the pipe manufacturing, mainly polyethylene. The usage of plastic material pipes for irrigation, of lowest cost, has risen in the latest years. The flexibility of these pipes leads to the internal diameter increase with pressure increase, fact already observed in research and that are not taken into account by mathematics equating used to determine the head loss. This paper proposes a model where it takes into account the elastic module (E) of the pipe to determine the diameter alteration in elastic pipes due to the pressure, affecting the determination of continuous head loss. Elastic Module proposed associated to Universal Equation, showed average performance rate of 0,9% being considered a extremely good estimative of reality.

Orientador: Carlos Roberto Grandini / Banca: Waldek Wladimir Bose Filho / Banca: Sandra Giacomin Schneider / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Resumo: Os recentes avanços científicos permitiram um aumento significativo na qualidade de vida e por consequência, na longevidade. Como consequência disso, a população de idosos aumentou consideravelmente e com isso, doenças relacionadas à idade como osteoporose levam o governo a ter que gastar consideráveis quantias em próteses ortopédicas. Há também uma grande demanda devido aos acidentes de trânsito. Os materiais metálicos mais usados na manufatura de próteses são divididos em três grupos: aços inoxidáveis, ligas a base de Co e ligas a base de Ti. Dentre estes três grupos, os biomateriais mais utilizados são aqueles a base de Ti, pois apresentam excelente biocompatibilidade e elevada resistência à corrosão. A liga de Ti mais utilizada para aplicações biológicas é a liga Ti-6Al-4V, porém alguns estudos associam o V a efeitos citotóxicos e reações adversas em tecidos, enquanto o Al tem sido associado com desordens neurológicas. Para sanar este problema, novas ligas de Ti que apresentam em sua composição elementos como Nb, Ta, Zr, Fe e Mo estão sendo pesquisadas e o desenvolvimento de novas ligas de Ti contendo Nb para aplicação ortopédica é um tema de grande importância social e tecnológica, pois o Nb é um elemento não tóxico e não alergênico, possui elevada biocompatibilidade e tem o Brasil como seu maior produtor, daí a importância de desenvolvimento de ciência e tecnologia utilizando tal material. A presença de elementos intersticiais (O, C, N e H) altera de significativamente as propriedades mecânicas da liga, principalmente suas propriedades elásticas, causando endurecimento ou enfraquecimento da liga. As medidas de espectroscopia mecânica são uma ferramenta poderosa para o estudo da interação destes elementos substitucionais e intersticiais com os elementos que compõem a liga. Este trabalho apresenta o efeito... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Recent scientific advances have led to a significant increase in life's quality and consequently, longevity. As a result, the elderly population has increased considerably and thus age-related disease such as osteoporosis lead the government to spend considerable sums of money with orthopedic prostheses. There is also a great demand for orthopedic prostheses due to accidents. The metallic materials commonly used in the manufacture of prostheses are divided into three groups: stainless steel, Co-based alloys and Ti-based alloys. Among these three groups, the most widely used as a biomaterial are the Ti-based alloys, since they have excellent biocompatibility and high corrosion resistance. The most used Ti-based alloy for biological applications is the Ti-6Al-4V alloy, but some studies associate the V to the cytotoxic effects and adverse reactions in tissues, while Al has been associated with neurological disorders. To solve this problem, new Ti-based alloys that have in their composition elements such as Nb, Ta, Zr, Fe and Mo are being researched. The development of new Ti-based alloys containing Nb for orthopedic application is a topic of great social and technological relevance, as this element is a non-toxic, non allergenic, has high biocompatibility and has Brazil as its biggest producer, hence the importance of development of science and technology using this material. The presence of interstitial elements (O, C, N and H) changes significantly the mechanical properties of the alloy, particularly its elastic properties, causing hardening or softening of the alloy. Mechanical spectroscopy measurements represent a powerful tool for studying the interaction of substitutional and interstitial elements with the metal matrix. This work presents the effect of interstitial oxygen in solid solution in some mechanical properties and biocompatibility of two alloys of the Ti-Nb system... (Complete abstract click electronic access below) / Mestre

Nos projetos hidráulicos de irrigação são contabilizadas as perdas de carga totais, que seriam as perdas contínuas ou principais e as localizadas, objetivando maximizar a uniformidade de distribuição de água, caracterizando um conjunto motobomba adequado ao sistema de irrigação e com isso, minimizando os custos anuais e de implantação do projeto. Com o uso da informática, problemas de cálculos complexos são resolvidos com muita facilidade; desta forma pode-se aplicar modelos mais complexo para calculo da perda de carga nos sistemas de irrigação, resultando em valores mais próximos da realidade, com maiores riquezas de detalhes. A perda de carga representa a dissipação de energia da água em forma de calor, ao longo da tubulação, decorrente da resistência ao escoamento oferecida pela viscosidade do fluido e pela inércia das partículas. É variável de acordo com o tamanho das rugosidades da parede do tubo, diâmetro da tubulação e com a velocidade da água. A indústria de plásticos e seus derivados, com o auxilio da engenharia, tem aprimorado a qualidade dos materiais destinados à fabricação dos tubos, principalmente de polietileno. A utilização de tubos fabricados de matérias plásticos, de menor custo, destinados à irrigação tem aumentado nos últimos anos. A flexibilidade desses tubos traz como consequência o aumento do diâmetro interno com o aumento da pressão, fato este já observado em pesquisa e que não são levados em consideração pelos equacionamentos matemáticos utilizados para determinação da perda de carga. O presente trabalho propõe um modelo onde leva em consideração o módulo de elasticidade (E) do tubo para determinar a alteração do diâmetro em tubos elásticos provocada pela pressão, afetando assim a determinação da perda de carga contínua. Conhecer detalhadamente a causa da perda de energia, com intuito de cada vez mais otimizar a energia gasta por área irrigada no cenário brasileiro, passa a ser de fundamental importância. O Modelo Elástico proposto associado à Equação Universal, apresentou índice de desempenho médio de 0,9 sendo considerado com uma estimativa muito boa da realidade. / Total head losses are accounted in the irrigation hydraulic projects, that would be the continuous losses and the local head losses, aiming to maximize the uniformity of water distribution, characterizing an adequate pump set to the irrigation system e thus, minimizing the project implantation and annual costs. With informatics support, complex calculation problems are solved with ease, therefore it is possible to apply more complex models for head loss calculation in the irrigation system, resulting in values closer to the reality, with greater details. The head loss represents the water energy dissipation as heat, along the piping, due to the resistance to the flow offered by the fluid viscosity and by the particles inertia. It is variable according to the size of the rugosities of the pipe wall, piping diameter and the water velocity. plastic industry and its derivates, with engineering support, have improved the quality of the materials for the pipe manufacturing, mainly polyethylene. The usage of plastic material pipes for irrigation, of lowest cost, has risen in the latest years. The flexibility of these pipes leads to the internal diameter increase with pressure increase, fact already observed in research and that are not taken into account by mathematics equating used to determine the head loss. This paper proposes a model where it takes into account the elastic module (E) of the pipe to determine the diameter alteration in elastic pipes due to the pressure, affecting the determination of continuous head loss. Elastic Module proposed associated to Universal Equation, showed average performance rate of 0,9% being considered a extremely good estimative of reality.

Um filme polimérico utilizado na fabricação de curativos adesivos não perfurados deve ter baixo módulo de elasticidade e boa permeabilidade ao vapor d\' água. O baixo módulo de elasticidade garante sensação de maior conforto do produto em contato com a pele quando a pessoa que o está utilizando movimenta a parte do corpo sobre a qual está aplicado o curativo, principalmente a região das articulações, como joelhos e cotovelos. A importância de uma boa permeabilidade ao vapor d\' água está relacionada, principalmente em curativos não perfurados, ao fato de que a pele perde água constantemente e, se o filme polimérico não permitir a saída dessa água ao meio ambiente, ocorrerá um fenômeno denominado maceração, que é a sensibilização excessiva da pele, causada pela hiper hidratação da mesma. O presente trabalho apresenta um estudo da permeabilidade ao vapor d\' água, bem como a caracterização vibracional e térmica de um filme polimérico constituído por três polímeros diferentes, desenvolvido para substituir a poliuretana utilizada atualmente na produção de curativos adesivos não perfurados, com custo inferior. Os polímeros que constituem o filme foram caracterizados separadamente e alguns resultados obtidos, como Tm e a estrutura química dos polímeros Lotader® e Lotryl® foram comparados aos dados fornecidos pelo fabricante. Verificou-se que as propriedades de módulo de elasticidade e permeabilidade ao vapor d\' água do filme desenvolvido são inferiores às da poliuretana inviabilizando a substituição. Entretanto, o trabalho proporcionou um melhor entendimento dos fatores que influenciam o módulo de elasticidade e a permeabilidade do novo material ao vapor d\' água. / A polymeric film must have low elasticity modulus and good water vapor permeation to be used in the production of non perforated adhesive tapes. Low modulus is desirable to provide comfort sensation as the consumer moves the part of his or her body in which the tape is applied on, mainly in the articulations regions, as elbows and knees. The importance of good water vapor permeation is related, mainly in the case of non perforated adhesive tapes with the continuous loss of water by the skin. If the film does not allow the release of the water continuously lost by the skin to the environment, the skin will become very sensitiveness as a result of over hydration. This work presents a study of water permeability and a thermal and vibrational characterization of a polymeric film composed of three different polymers developed to replace the adhesive not perforated polyurethane tape providing lower cost. Besides characterization a test of Water Vapor Transmission Rate (WVTR) was performed. Each polymer present in the film composition was analyzed and the results as Tm and chemical structure of Lotader® e Lotryl® were compared with the producer data. It was verified that the properties of elasticity modulus and water vapor permeability of the new material developed are worse than polyurethane so the substitution can not be performed. However, the work provided a better understanding of the factors that influences the elasticity modulus and water vapor permeability of the new material.

Um filme polimérico utilizado na fabricação de curativos adesivos não perfurados deve ter baixo módulo de elasticidade e boa permeabilidade ao vapor d\' água. O baixo módulo de elasticidade garante sensação de maior conforto do produto em contato com a pele quando a pessoa que o está utilizando movimenta a parte do corpo sobre a qual está aplicado o curativo, principalmente a região das articulações, como joelhos e cotovelos. A importância de uma boa permeabilidade ao vapor d\' água está relacionada, principalmente em curativos não perfurados, ao fato de que a pele perde água constantemente e, se o filme polimérico não permitir a saída dessa água ao meio ambiente, ocorrerá um fenômeno denominado maceração, que é a sensibilização excessiva da pele, causada pela hiper hidratação da mesma. O presente trabalho apresenta um estudo da permeabilidade ao vapor d\' água, bem como a caracterização vibracional e térmica de um filme polimérico constituído por três polímeros diferentes, desenvolvido para substituir a poliuretana utilizada atualmente na produção de curativos adesivos não perfurados, com custo inferior. Os polímeros que constituem o filme foram caracterizados separadamente e alguns resultados obtidos, como Tm e a estrutura química dos polímeros Lotader® e Lotryl® foram comparados aos dados fornecidos pelo fabricante. Verificou-se que as propriedades de módulo de elasticidade e permeabilidade ao vapor d\' água do filme desenvolvido são inferiores às da poliuretana inviabilizando a substituição. Entretanto, o trabalho proporcionou um melhor entendimento dos fatores que influenciam o módulo de elasticidade e a permeabilidade do novo material ao vapor d\' água. / A polymeric film must have low elasticity modulus and good water vapor permeation to be used in the production of non perforated adhesive tapes. Low modulus is desirable to provide comfort sensation as the consumer moves the part of his or her body in which the tape is applied on, mainly in the articulations regions, as elbows and knees. The importance of good water vapor permeation is related, mainly in the case of non perforated adhesive tapes with the continuous loss of water by the skin. If the film does not allow the release of the water continuously lost by the skin to the environment, the skin will become very sensitiveness as a result of over hydration. This work presents a study of water permeability and a thermal and vibrational characterization of a polymeric film composed of three different polymers developed to replace the adhesive not perforated polyurethane tape providing lower cost. Besides characterization a test of Water Vapor Transmission Rate (WVTR) was performed. Each polymer present in the film composition was analyzed and the results as Tm and chemical structure of Lotader® e Lotryl® were compared with the producer data. It was verified that the properties of elasticity modulus and water vapor permeability of the new material developed are worse than polyurethane so the substitution can not be performed. However, the work provided a better understanding of the factors that influences the elasticity modulus and water vapor permeability of the new material.

Detta examensarbete presenterar resultat från en laboratoriestudie på en lera från Enköping stabiliserad med kalk och cement. I laboratoriet har isotropiskt konsoliderade odränerade aktiva triaxialförsök utförts på provkroppar och jämförts med enaxliga tryckförsök som utförts på provkroppar från samma inblandningstillfälle. De två metoderna har visat sig ge likvärdiga värden på utvärderad odränerad skjuvhållfasthet. Elasticitetsmodulen har däremot visat sig vara mycket högre för triaxialförsöken än enaxliga tryckförsök. För triaxialförsöken har förhållandet mellan sekantmodulen och den odränerade skjuvhållfastheten legat mellan 112-333. För de enaxliga tryckförsöken ligger förhållandet mellan sekantmodulen och den odränerade skjuvhållfastheten inom intervallet 44-146. Inget mönster har dock kunnat urskiljas då förhållandet mellan de två olika försöken har varierat mellan 1,0-3,5. Ett lägre och högre back pressure användes under triaxialförsöken. Till skillnad från tidigare studier har dock båda dessa back pressures vattenmättat provkroppen. Resultaten visar på att back pressure inte påverkar testresultaten, förutsatt att provet blivit fullt vattenmättat. Utöver denna jämförelse har ytterligare passiva triaxialförsök utförts. De passiva triaxialförsöken har utförts som isotropiskt konsoliderade odränerade försök.. Däremot har två olika metoder använts under skjuvningsfasen. I första typen av försök har den axiella spänningen minskats medan den radiella spänningen har hållits konstant. I den andra typen av försök har i stället den radiella spänningen ökats samtidigt som den axiella spänningen har hållits konstant. Skjuvhållfastheter har jämförts med resultat från kalkpelarsondering i fält och visar på att skjuvhållfastheten genomgående varit högre i fält än i laboratoriet. Dessutom har skjuvhållfastheter och elasticitetsmoduler testats efter olika lagringstider genom enaxliga tryckförsök. / This master thesis presents results from a laboratory study on a clay from Enköping which was stabilized with lime and clay. Isotropic consolidated undrained compressive tests were performed on samples and compared to unconfined compressive testing. The two methods have shown no difference in the evaluation of undrained shear strength. However the modulus of elasticity was shown to be much higher for the triaxial tests. For the unconfined compressive tests the relation between the undrained shear strength and secant modulus was within the range of 44-146. The equivalent for the triaxial tests was in the interval of 112-333. However no pattern was extinguishable between the two tests as this relation has varied between 1,0 to 3,5. A lower and higher back pressure was used during the triaxial testing. However, both back pressures have succeeded in saturating the sample. Results show that the back pressure has little effect on the results, as long as the sample has been fully saturated. In addition to this extension tests were performed on samples as well. The tests performed were isotropic consolidated undrained. However two different shearing methods were used. The first test was strain rate dependant while the second test was stress rate dependant. In the first test the vertical stress decreased while the radial stresses were kept constant, while in the other test the radial stresses increased while the vertical stress were kept constant. The undrained shear strength was compared to lime/cement column penetration tests in field. Results showed that tests in field show a much higher undrained shear strength than laboratory testing.

In recent times, light gauge cold-formed steel sections have been used extensively in residential, industrial and commercial buildings as primary load bearing structural components. This is because cold-formed steel sections have a very high strength to weight ratio compared with thicker hot-rolled steel sections, and their manufacturing process is simple and cost-effective. However, these members are susceptible to various buckling modes including local and distortional buckling and their ultimate strength behaviour is governed by these buckling modes. Fire safety design of building structures has received greater attention in recent times due to continuing loss of properties and lives during fires. Hence, there is a need to fully evaluate the performance of light gauge cold-formed steel structures under fire conditions. Past fire research has focused heavily on heavier, hot-rolled steel members. The buckling behaviour of light gauge cold-formed steel members under fire conditions is not well understood. The buckling effects associated with thin steels are significant and have to be taken into account in fire safety design. Therefore, a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the distortional buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research program more than 115 tensile coupon tests of light gauge cold-formed steels including two steel grades and five thicknesses were conducted at elevated temperatures. Accurate mechanical properties including the yield strength, elasticity modulus and stress-strain curves were all determined at elevated temperatures since the deterioration of the mechanical properties is one of the major parameters in the structural design under fire conditions. An appropriate stress-strain model was also developed by considering the inelastic characteristics. The results obtained from the tensile coupon tests were then used to predict the ultimate strength of cold-formed steel compression members. In the second phase of this research more than 170 laboratory experiments were undertaken to investigate the distortional buckling behaviour of light gauge coldformed steel compression members at ambient and elevated temperatures. Two types of cross sections were selected with various thicknesses (nominal thicknesses are 0.6, 0.8, and 0.95 mm) and both low and high strength steels (G250 and G550 steels with minimum yield strengths of 250 and 550 MPa). The experiments were conducted at six different temperatures in the range of 20 to 800°C. A finite element model of the tested compression members was then developed and validated with the help of experimental results. The degradation of mechanical properties with increasing temperatures was included in finite element analyses. An extensive series of parametric analyses was undertaken using the validated finite element model to investigate the effect of all the influential parameters such as section geometry, steel thickness and grade, mechanical properties and temperature. The resulting large data base of ultimate loads of compression members subject to distortional buckling was then used to review the adequacy of the current design rules at ambient temperature. The current design rules were reasonably accurate in general, but in order to improve the accuracy further, this research has developed new design equations to determine the ultimate loads of compression members at ambient temperature. The developed equation was then simply modified by including the relevant mechanical properties at elevated temperatures. It was found that this simple modification based on reduced mechanical properties gave reasonable results, but not at higher temperatures. Therefore, they were further modified to obtain a more accurate design equation at elevated temperatures. The accuracy of new design rules was then verified by comparing their predictions with the results obtained from the parametric study. This thesis presents a description of the experimental and numerical studies undertaken in this research and the results including comparison with simply modified current design rules. It describes the laboratory experiments at ambient and elevated temperatures. It also describes the finite element models of cold-formed steel compression members developed in this research that included the appropriate mechanical properties, initial geometric imperfections and residual stresses. Finally, it presents the details of the new design equations proposed for the light gauge coldformed steel compression members subjected to distortional buckling effects at elevated temperatures.

Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load bearing structural elements and non-load bearing structural elements (partitions) due to their advantages such as higher strength to weight ratio over the other structural materials such as hot-rolled steel, timber and concrete. Cold-formed steel members are often made from thin steel sheets and hence they are more susceptible to various buckling modes. Generally short columns are susceptible to local or distortional buckling while long columns to flexural or flexural-torsional buckling. Fire safety design of building structures is an essential requirement as fire events can cause loss of property and lives. Therefore it is essential to understand the fire performance of light gauge cold-formed steel structures under fire conditions. The buckling behaviour of cold-formed steel compression members under fire conditions is not well investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research, a detailed review was undertaken on the mechanical properties of light gauge cold-formed steels at elevated temperatures and the most reliable predictive models for mechanical properties and stress-strain models based on detailed experimental investigations were identified. Their accuracy was verified experimentally by carrying out a series of tensile coupon tests at ambient and elevated temperatures. As the second phase of this research, local buckling behaviour was investigated based on the experimental and numerical investigations at ambient and elevated temperatures. First a series of 91 local buckling tests was carried out at ambient and elevated temperatures on lipped and unlipped channels made of G250-0.95, G550-0.95, G250-1.95 and G450-1.90 cold-formed steels. Suitable finite element models were then developed to simulate the experimental conditions. These models were converted to ideal finite element models to undertake detailed parametric study. Finally all the ultimate load capacity results for local buckling were compared with the available design methods based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Part 1.2 and the direct strength method (DSM), and suitable recommendations were made for the fire design of cold-formed steel compression members subject to local buckling. As the third phase of this research, flexural-torsional buckling behaviour was investigated experimentally and numerically. Two series of 39 flexural-torsional buckling tests were undertaken at ambient and elevated temperatures. The first series consisted 2800 mm long columns of G550-0.95, G250-1.95 and G450-1.90 cold-formed steel lipped channel columns while the second series contained 1800 mm long lipped channel columns of the same steel thickness and strength grades. All the experimental tests were simulated using a suitable finite element model, and the same model was used in a detailed parametric study following validation. Based on the comparison of results from the experimental and parametric studies with the available design methods, suitable design recommendations were made. This thesis presents a detailed description of the experimental and numerical studies undertaken on the mechanical properties and the local and flexural-torsional bucking behaviour of cold-formed steel compression member at ambient and elevated temperatures. It also describes the currently available ambient temperature design methods and their accuracy when used for fire design with appropriately reduced mechanical properties at elevated temperatures. Available fire design methods are also included and their accuracy in predicting the ultimate load capacity at elevated temperatures was investigated. This research has shown that the current ambient temperature design methods are capable of predicting the local and flexural-torsional buckling capacities of cold-formed steel compression members at elevated temperatures with the use of reduced mechanical properties. However, the elevated temperature design method in Eurocode 3 Part 1.2 is overly conservative and hence unsuitable, particularly in the case of flexural-torsional buckling at elevated temperatures.

The importance of fire safety design has been realised due to the ever increasing loss of properties and lives caused by structural failures during fires. In recognition of the importance of fire safety design, extensive research has been undertaken in the field of fire safety of buildings and structures especially over the last couple of decades. In the same period, the development of fire safety engineering principles has brought significant reduction to the cost of fire protection. However the past fire research on steel structures has been limited to heavier, hot-rolled structural steel members and thus the structural behaviour of light gauge cold-formed steel members under fire conditions is not well understood. Since cold-formed steel structures have been commonly used for numerous applications and their use has increased rapidly in the last decade, the fire safety of cold-formed steel structural members has become an important issue. The current design standards for steel structures have simply included a list of reduction factors for the yield strength and elasticity modulus of hot-rolled steels without any detailed design procedures. It is not known whether these reduction factors are applicable to the commonly used thin, high strength steels in Australia. Further, the local buckling effects dominate the structural behaviour of light gauge cold-formed steel members. Therefore an extensive research program was undertaken at the Queensland University of Technology to investigate the local buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. The first phase of this research program included 189 tensile coupon tests including three steel grades and six thicknesses to obtain the accurate yield strength and elasticity modulus values at elevated temperatures because the deterioration of the mechanical properties is the major parameter in the structural design under fire conditions. The results obtained from the tensile tests were used to predict the ultimate strength of cold-formed steel members. An appropriate stress-strain model was also developed by considering the inelastic mechanical characteristics. The second phase of this research was based on a series of more than 120 laboratory experiments and corresponding numerical analyses on cold-formed steel compression members to investigate the local bucking behaviour of the unstiffened flange elements, stiffened web elements and stiffened web and flange elements at elevated temperatures up to 800°C. The conventional effective design rules were first simply modified considering the reduced mechanical properties obtained from the tensile coupon tests and their adequacy was studied using the experimental and numerical results. It was found that the simply modified effective width design rules were adequate for low strength steel members and yet was not adequate for high strength cold-formed steel members due to the severe reduction of the ultimate strength in the post buckling strength range and the severe reduction ratio of the elasticity modulus to the yield strength at elevated temperatures. Due to the inadequacy of the current design rules, the theoretical, semi-empirical and empirical effective width design rules were developed to accurately predict the ultimate strength of cold-formed steel compression members subject to local buckling effects at elevated temperatures. The accuracy of these new design methods was verified by comparing their predictions with a variety of experimental and numerical results. This thesis presents the details of extensive experimental and numerical studies undertaken in this research program and the results including comparison with simply modified effective width design rules. It also describes the advanced finite element models of cold-formed steel compression members developed in this research including the appropriate mechanical properties, initial imperfections, residual stresses and other significant factors. Finally, it presents the details of the new design methods proposed for the cold-formed steel compression members subject to local buckling effects at elevated temperatures.

Dreiaxiale Druckprüfungen können als Einstufenversuche, als Mehrstufenversuche oder als Versuche mit kontinuierlichen Bruchzuständen ausgeführt werden. Bei der Anwendung der Mehrstufentechnik ergeben sich insbesondere Fragestellungen hinsichtlich der richtigen Wahl des Umschaltpunktes und des optimalen Verlaufs des Spannungspfades zwischen den einzelnen Versuchsstufen. Fraglich beim Versuch mit kontinuierlichen Bruchzuständen bleibt, ob im Versuchsverlauf tatsächlich Spannungszustände erfasst werden, welche die Höchstfestigkeit des untersuchten Materials repräsentieren. Die Dissertation greift diese Fragestellungen auf, ermöglicht den Einstieg in die beschriebene Thematik und schafft die Voraussetzungen, die zur Lösung der aufgeführten Problemstellungen notwendig sind. Auf der Grundlage einer umfangreichen Datenbasis gesteinsmechanischer und petrophysikalischer Kennwerte wurde ein numerisches Modell entwickelt, welches das Spannungs-Verformungs-, Festigkeits- und Bruchverhalten eines Sandsteins im direkten Zug- und im einaxialen Druckversuch sowie in dreiaxialen Druckprüfungen zufriedenstellend wiedergibt. Das Festigkeitsverhalten des entwickelten Modells wurde in Mehrstufentests mit unterschiedlichen Spannungspfaden analysiert und mit den entsprechenden Laborbefunden verglichen.