No description available.

[pt] Este trabalho tem como objetivo investigar o desempenho e a resistência de cantoneiras curtas de abas iguais pultrudadas em polímero reforçado com fibra de vidro (PRFV) submetidas à compressão centrada de curta duração. Os fundamentos teóricos associados ao comportamento de cantoneiras perfeitas e reais são apresentados e os resultados de um programa experimental que envolveu caracterização dos materiais e ensaios à compressão são reportados e discutidos. Ao todo, vinte e uma colunas bi-engastadas com diferentes razões largura/espessura das abas, comprimentos e propriedades mecânicas foram testadas. As forças críticas experimentais para o modo de flambagem à flexo-torção foram determinadas e comparadas com as previsões teóricas, apresentando boa concordância. A resistência à compressão de cada coluna foi obtida experimentalmente, discutindo-se a influência do comportamento pós-flambagem e das imperfeições na capacidade de carga final com relação à esperada para coluna perfeita e, finalmente, uma equação para resistência de coluna é proposta para resolver o problema. / [en] This paper aims to investigate performance and strength of glass-fiber reinforced polymer (GFRP) pultruded short equal leg angle columns subject to short-term concentric compression. Background theories associated with the behavior of perfect and real angle struts are presented and the results of an experimental program that involved material characterization and compression tests are reported and discussed. In all, twenty-one fixed-ended columns having different leg width-to-thickness ratio and lengths and mechanical properties were tested. Experimental critical loads for flexural-torsional buckling mode were determined and compared with theoretical predictions, showing a good agreement with each other. Compressive strength for each column was obtained, the influence of post-buckling behavior and imperfections in the final load-carrying capacity with respect to that expected for perfect column condition is discussed and, finally, a column strength equation is proposed to address the problem.

Glass fibre composites are common materials used in high voltage applications as insulating materials that provide good structural integrity. The aim of this thesis is to develop a method of studying the failure in such materials by measuring the dielectric strength on micro- and meso- scale samples, consisting of single fibre filaments and fibre bundles respectively embedded in epoxy resin. To do this, a body of relevant knowledge has been amassed, which is complemented with finite element analysis giving detailed insight into the electric field distribution in the microstructure of fibre composites. A method of producing virtually defect free single fibre samples has been developed where a filament is hung down tubes and cast in epoxy resin. A similar method was developed for producing bundle samples, however this needs some slight correction in order to prevent exothermic reactions. The dielectric strength of these samples are measured by applying a continuously increasing voltage until discharge is recorded. To evaluate the method micro- and meso- scale samples were prepared of three different fibres and their dielectric strengths measured. This evaluation showed that the method can be used to measure a definitive lower bound in the dielectric strength of fibre composites. However, the method can not definitively determine the location of the discharge, which is necessary to verify conclusions about the materials properties. To progress the method, the dielectric strength of neat epoxy samples of the same dimensions as the fibre composite samples should be investigated. Increasing the tolerance of the measurement setup should also be investigated as this could help by increasing the power of the discharge leading to more severe damage in the material.

No description available.

[pt] Nas últimas décadas, perfis pultrudados de polímeros reforçados com fibra (PRF) vêm despertando grande interesse na indústria civil devido a sua alta relação entre resistência e peso e sua aplicabilidade em ambientes agressivos. Apesar de apresentar grande resistência às intempéries, a degradação dos PRF foi notada após anos de exposição em campo. A utilização de ensaios não destrutivos (END) se mostra como uma boa alternativa para avaliar a integridade deste material, havendo especial interesse para controle de qualidade de baixo custo em campo. Dessa forma, este trabalho utilizou ensaios de vibração livre com duas técnicas de excitação por impulso para detectar danos em polímeros reforçados com fibra de vidro envelhecidos em câmaras com elevada temperatura, umidade e salinidade. Através da avaliação das frequências naturais e amortecimentos, foi observado o impacto das condições ambientais na integridade do material, resultado corroborado pela variação das propriedades elásticas obtidas através da resposta dinâmica acústica. / [en] In the last decades, pultruded profiles of fiber-reinforced polymers (FRP) have been attracting great interest in the civil industry due to their high strength-to-weight ratio and their applicability in aggressive environments. Despite showing great resistance to weathering, the degradation of FRP was noticed after years of exposure in the field. The use of non-destructive techniques (NDT) has been shown to be a good alternative to evaluate the integrity of this material, with special interest for low-cost quality control in the field. Thus, this work used free vibration tests with two impulse excitation techniques to detect damage in glass fiber reinforced polymers aged in chambers with high temperature, humidity and salinity. Through the evaluation of natural frequencies and damping, the impact of environmental conditions on the integrity of the material was observed, a result corroborated by the variation of elastic properties obtained through the acoustic dynamic response.

During 2021–2022 a new school was constructed in Älmhult, Sweden, using a precast concrete framework. The sandwich walls for the building were produced by the precast manufacturer Torps Byggelement in Alvesta, Sweden. To connect the concrete layer a kind of sandwich connector made of glass fiber reinforced polymer (GFRP) was used that the manufacturer had no previous experience with. This graduation thesis was conducted to compare this GFRP connector system with a traditional system made of stainless steel. The two systems were designed for an identical reference sandwich wall and the two resulting walls were compared with regards to thermal properties, manufacturing process and costs for the manufacturer. The thermal properties were evaluated by modelling in a finite element analysis program that calculated equivalent thermal transmittance. Manufacturing was compared through an interview with employees at the precast manufacturer. Finally, costs were compared by summarizing the cost of components needed from each connector system. The results of the study showed a decrease of 6,7 percent in thermal transmittance when the GFRP connectors were used instead of stainless steel connectors. The thermal bridging effect of GFRP connectors was negligible. In terms of manufacturing, the GFRP connector that was studied was considered by the manufacturer to be preferable to the other system in some regards and equal in others. The total cost of components was considerably higher with GFRP connectors but increased value because of reduced thermal transmittance, reduced labour costs during manufacturing and possible reduction in isolation waste should be considered.

[pt] O comportamento de vigas de concreto armado com barras de polímero reforçado com fibras de vidro (PRFV) submetidas ao esforço cortante tem diferenças quando comparada ao tradicional uso de armaduras de aço. O relativo baixo módulo de elasticidade e menor resistência ao carregamento transversal de barras de PRFV alteram a ação dos mecanismos de resistência e cinemática da fissura crítica ao cortante. Nesse contexto, a aplicação de fibras dispersas na matriz de concreto se coloca como uma possibilidade para buscar a redução da flexibilidade desse tipo de elemento. Sendo assim, este trabalho investiga o comportamento experimental de quatro vigas de concreto armado com barras de PRFV sem e com estribos e fibras de basalto. Utilizando-se da técnica de Correlação de Imagem Digital (CID), os campos de deslocamentos do vão de ruptura foram mapeados e, por meio de modelos constitutivos dos mecanismos resistentes à força cortante disponíveis na literatura, analisou-se o comportamento resistente das vigas. A quantificação de resistência através dos modelos constitutivos apresentou uma satisfatória correlação com os resultados experimentais. Além disso, a análise possibilitou uma melhor compreensão da contribuição dos mecanismos resistentes em diferentes estágios de carregamento. / [en] The shear behavior of reinforced concrete beams with Glass Fiber Reinforced Polymer Bars (GFRP) has differences when compared to traditional steel reinforcement. The relative low modulus of elasticity and the lower resistance to transverse loading of GFRP bars change the resistance mechanisms and kinematics of the critical shear crack. In this context, the application of dispersed fibers in the concrete matrix may be used to try to reduce the flexibility of this type of element. Therefore, this work investigates the experimental behavior of four reinforced concrete beams with GFRP bars with and without stirrups and basalt fibers. By using Digital Image Correlation (DIC) technique, the displacement fields of the failure span were mapped and, by means of constitutive models of the shear resistant mechanisms available in the literature, the resistant behavior of the beams was analyzed. The evaluation of resistance mechanisms through the constitutive models showed a satisfactory correlation with the experimental results. In addition, the analysis provided a better understanding of the contribution of each resistant mechanisms at different stages of loading.

Yes / This paper investigates the strength and ductility of concrete confined by Glass/Epoxy ±55° Filament Wound Pipes (GFRP) under axial compression. A total of 24 cylinderical specimens were prepared with expansive and Portland cements, properly compacted and un-compacted for different composite fresh concrete matrix. Test results showed that compressive strength and axial deformation at failure of concrete confined with GFRP tubes increased by an average of 2.85 and 5.57 times these of unconfined concrete, respectively. Macro and micro analyses of GFRP pipes after failure were also investigated. Debonding, whitening, matrix/transfer cracking, delamination and splitting mechanisms were detected at failure, respectively. The experimental results were also employed to assess the reliability of design models available in the literature for confined concrete compressive strength.

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24590号 / 工博第5096号 / 新制||工||1976(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 杉浦 邦征, 教授 山本 貴士, 准教授 北根 安雄 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM