No description available.

Liquefaction of soil is one of the major contributing factors for damages of infrastructures and utility services during earthquake. Liquefaction occurs when short strong shaking creates undrained loading condition in saturated soil deposit thereby increases pore water pressure, which eventually equals the effective confining pressure resulting in significant reduction in shear strength and bearing capacity of soil deposit. Several studies have been conducted to investigate the effect of polypropylene fiber on sand deposit as a measure to prevent liquefaction but most of them are based on static tests. Therefore, the present study, tries to understand liquefaction characteristics of sand reinforced with polypropylene fiber based on cyclic triaxial test. The main objectives of this study are (i) to explore the effect of polypropylene fiber on pore pressure generation and deformation characteristics of sand, and (ii) to observe the effect of confining pressure on liquefaction characteristics of sand-fiber mixture. A series of stress controlled cyclic triaxial tests were performed at 5 and 10 psi effective confining pressures. At 5 psi effective confining pressure, specimens of clean sand, and sand containing 0.05, 0.075, 0.1, and 0.3% polypropylene fiber by dry weight were tested at 0.2, 0.25, 0.3, and 0.4 Cyclic Stress Ratio (CSR). However, at 10 psi effective confining pressure, specimens were also tested for 0.5%, and 0.75% fiber in addition to those at 5 psi confining pressure at 0.2, 0.3, and 0.4 CSR. Based on the test results, it was observed that, cyclic shear stress increases with the increase in initial effective confining pressure. Also, for a given CSR, liquefaction resistance decreased with the increase in effective confining pressure. Furthermore, significant improvement in liquefaction resistance was observed when the fiber content exceeded beyond 0.075% at 5 psi confining stress. However, at 10 psi confining pressure, addition of fiber did not help in improvement of liquefaction resistance of sand except when cyclic shear stress was applied at 0.2 CSR. At 0.2 CSR, although the specimens did liquefy based on pore pressure generation criteria at all fiber contents, specimens containing 0.5% and 0.75% fiber did not ever reach 2.5% and 5% DA (Double Amplitude) deformation throughout 1000 loading cycles.

Master of Science / Department of Civil Engineering / Asadollah Esmaeily / Engineers involved in construction face various challenges. One of them being dealing with cracks in concrete. Naturally, concrete is weak in tension defining its bristle characteristics. To compensate, fiber reinforcement is used in the concrete mixes. Popular fiber types are steel, glass, polypropylene, and carbon fibers. These types of fibers are used to reinforce concrete. These fibers all increase the tensile and flexural strength of concrete. Additionally, they all have their own advantages. This paper is oriented to briefly introduce basic properties of these fibers. This includes the composition, production, advantages, applications, and restrictions of the mentioned fibers.

For evaluation and quality control of concrete structures, the impact resonant frequency method is widely accepted for monitoring structure in-service properties and detecting structural damage. Common defects in concrete include consolidation problems during casting and development of micro-cracks during stages of hydration. Monitoring the dynamic characteristics of concrete plays an essential role in detecting real-time and early stages of deterioration. Ample research is focused on detecting large defects, however not much information is available on detection of minor defects of composites like fiber reinforced concrete. Change of elastic behavior when Polypropylene fibers are added as reinforcement is investigated. Destructive tests on structures in-service are not always feasible thus leaving non-destructive condition assessment as the only option. Amongst the various non-destructive tests available, vibrational tests provide a practical method to predict the dynamic moduli of structures (dynamic modulus of elasticity, dynamic modulus of rigidity and dynamic Poisson’s ratio). The objective of this research is to assess the dynamic elastic properties of Polypropylene Fiber Reinforced Concrete (PFRC) in correlation with induced cracks and common consolidation defects using a lab developed non-destructive testing method that relies on impulse excitation and stress wave propagation to measure changes in the resonant frequency when polypropylene fibers are added to concrete. In the experimental program, two fiber sizes, macro and micro, with various volume contents have been used for casting PFRC cylinders and prisms. Fundamental resonant frequencies were measured for all cylinders and prisms in the transverse and longitudinal directions. All measured frequencies are directly related to the low-strain dynamic modulus of elasticity. In addition, PFRC prisms were used to investigate the relationship between the dynamic modulus of elasticity and modulus of rigidity. Several batches of similar mixtures are used to investigate different parameters that affect the resonant frequency of concrete such as the water to cement ratio, curing condition and age. Results indicated a decrease in the resonant frequency and elastic properties with an increase of the fiber content or length. Micro fibers showed higher dynamic elastic moduli when compared to macro fibers of the same mixture under saturated curing conditions. Post-cracked PFRC cylinders and flexural fractured prisms retained some of the resonant frequency with macro fibers exhibiting better elastic recovery when cracked. / Graduate

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / n this article, the geotechnical behavior of the reinforced soil is studied through additions of polypropylene fiber and recycled glass powder, this in order to obtain a homogeneously reinforced soil matrix to reduce possible structural failures, differential settlements and increase capacity bearing. The sample used was classified as a clay soil with low plasticity (CL) and with moderately expansive characteristics, based on the values of the Liquid Limit, Plastic Limit and Plasticity Index. The effect of the 1% polypropylene fiber and different amounts of recycled glass powder (0%, 4%, 5%, 6.5%), with respect to dry weight is analyzed in this soil. The purpose of varying the quantity of these materials is to find a trend of the strength parameters and obtain the optimal percentages that provides improvements in geotechnical behavior. Modified Proctor and Direct Shear tests were carried out, this latter to obtain the shear strength parameters of the mixtures and compare them with the clay soil. Finally, the optimal result for soil improvement was the mixture made by 1% polypropylene fiber and 4% glass powder, which achieved an increase of the angle of friction and cohesion.

No description available.

No description available.

Seismic resistance of many buildings in Turkey is insufficient. Strengthening using R/C infills requires huge construction work. Feasible, easy strengthening techniques are being studied in Structural Mechanics Laboratory of METU. In this project, it was aimed to develop an economical strengthening method. This method is based on addition of steel fibers and/or PP fibers in mortar and application of mortar on masonry wall. Project was sponsored by the Scientific and Technical Research Council of Turkey (T&Uuml / BiTAK). Physical properties of cement, aggregate, and mortar used in tests were determined by material tests. After performing flexural strength and compressive strength tests, optimum mortar was obtained. R/C frames strengthened by applying the mortar to brick infilled walls were tested under reversed cyclic loads. Before the frame tests, two series of panel tests were performed to correctly model strengthened infill walls and to gather information about behavior of walls under load. Totally 10 frame tests were done. 4 tests were done as reference tests, and other 6 were done as strengthened frame tests. In the analytical part of study, the plastered hollow brick infill wall strengthened by FRM was modeled as two separate compression struts. First strut was used to model the plastered hollow brick infill wall. Second strut was used to model the FRM. This technique is effective in improving seismic behavior by increasing strength, initial stiffness, energy dissipation, and ductility. Moreover, the method provides strengthening of the buildings without evacuating the structure.

Apesar do avanço tecnológico crescente na construção civil, a falta de durabilidade das estruturas de concreto, tanto em edificações como pavimentação, tem sido constatada com acentuada assiduidade e proporção. O compósito cimentício de elevada deformação, também conhecido como Engineered Cementitious Composites (ECC), foi difundido a partir do conceito de concretos de alto desempenho reforçado com fibras, visando suprir o comportamento frágil do concreto convencional e problemas relacionados à falta de durabilidade gerada, principalmente, devido à propagação de fissuras. Neste contexto, o Laboratório de Ensaio de Modelos Estruturais (LEME) da Universidade Federal do Rio Grande do Sul (UFRGS) consolidou, nos últimos cinco anos, um grupo de pesquisa voltado ao estudo do ECC aliado a utilização de materiais nacionais. A concepção tem sido baseada na aplicação de materiais que proporcionem custos mais baixos e fomentem questões de sustentabilidade ambiental. Assim, foram incorporados ao material, fibra de polipropileno (2% em volume) e substituição parcial do cimento por 30% (em volume) de cinza de casca de arroz residual. O presente trabalho visa analisar questões de durabilidade destes compósitos (com e sem a incorporação de cinza), e compará-los a concretos convencionais, através de ensaios relacionados ao estudo da estrutura de poros (absortividade, absorção e índice de vazios, absorção e água por capilaridade, absorção de água pelo método do cachimbo e microscopia eletrônica de varredura), penetração e difusão de íons cloretos, retração livre e restringida, e, por fim, resistência à abrasão. Os resultados obtidos indicam que a incorporação de cinza de casca de arroz melhorou significativamente as propriedades do compósito relacionadas à conexão e solução dos poros, dificultando a passagem de cloretos, além de apresentar resistência à abrasão semelhante ao compósito de referência. Sua desvantagem está relacionada às maiores aberturas de fissuras ocasionadas devido à retração restringida. Entretanto, o trabalho evidencia a viabilidade e vantagem do uso de cinza de casca de arroz na produção do compósito, em termos de durabilidade. / Despite the increasing technological advances in construction, the lack of concrete structures durability, both in buildings and pavement, have been found with severe attendance and proportion. The high strain cementitious composite, also known as Engineered Cementitious Composites (ECC), was widespread from the concept of high performance fiber reinforced concrete, in order to supply the fragile behavior of conventional concrete and problems related to lack of durability generated mainly due to crack propagation. In this context, the Laboratório de Ensaios e Modelos Estruturais (LEME) of the Federal University of Rio Grande do Sul (UFRGS) consolidated over the last five years, a research group focused on the ECC study allied with the use of national materials. The design has been based on the application materials that provide lower costs and promote environmental sustainability issues. Thus, they were incorporated into the material polypropylene fibers (2% by volume) and partial cement replacement of 30% (by volume) of residual rice husk ash. This study aims to examine durability issues of these composites (with and without rice husk ash), and compare them to conventional concretes, through tests related to the study of pore structure (absorptivity, absorption and void ratio, water absorption by capillarity, water absorption by the pipe method and scanning electron microscopy), penetration and diffusion of chloride ions, free and restrained shrinkage, and, finally, abrasion resistance. The results indicate that the incorporation of rice husk ash significantly improved material properties related to connection and pores solution, hindering the chloride ingress, and presents abrasion resistance similar to the reference composite. Its disadvantage is related to the larger cracks due to restrained shrinkage. However, the work demonstrates the viability and advantage of use rice husk ash in the composite production in terms of durability.

O compósito cimentício de elevada capacidade de deformação é um tipo especial de compósito cimentício de alto desempenho reforçado com fibras, cuja principal característica é a alta ductilidade, devido à capacidade de gerar fissuração múltipla quando em carregamento. Este compósito também é conhecido como Engineered Cementitious Composite (ECC), desenvolvido pelo Pesquisador Professor Victor Li na Universidade de Michigan, nos Estados Unidos. Nos últimos cinco anos, o Laboratório de Ensaios e Modelos Estruturais (LEME) vem desenvolvendo uma linha de pesquisa com o objetivo de adaptar o ECC com materiais locais. Neste intuito, fibras de polipropileno têm sido utilizadas em conjunto com cinza da casca de arroz visando o desenvolvimento de misturas mais viáveis economicamente e mais ambientalmente sustentáveis. Este estudo teve como finalidade avaliar a possibilidade da utilização da cinza de casca de arroz residual (moída em laboratório por 1, 2, 4, 6 e 8 horas) como material pozolânico para substituição parcial de cimento. A caracterização da cinza foi realizada por meio dos ensaios de difração de raio-x, fluorescência de raio-x, perda ao fogo, índice de desempenho, massa especifica e distribuição granulométrica. Este estudo caracterizou compósitos cimentícios de elevada capacidade de deformação contendo 10%, 20% e 30% (em volume) de substituição de cimento por cinza de casca de arroz residual, analisando o comportamento mecânico quanto à tração direta e flexão a quatro pontos. Na busca de um indicativo de durabilidade foram avaliados a absorção e índice de vazios destes compósitos. Além disso, foi realizada a análise da curva de liberação de calor de hidratação para verificar o efeito retardador que a cinza de casca de arroz possa gerar no compósito. E como possível utilização deste compósito como material de reparo, foi analisada a aderência pelo método de cisalhamento oblíquo e pelo método de arrancamento e avaliada a reflexão de fissuras juntamente com a realização de microscopia eletrônica de varredura destes compósitos. Os resultados obtidos mostraram-se satisfatórios para os compósitos com 30% de cinza de casca de arroz moída por 8 e 4 horas, apresentando bons resultados quanto à ductilidade e resistência à propagação de fissuras. / The high strain cementitious composite is a special type of fiber reinforced high performance cementitious composite which main characteristic is the high ductility achieved through the ability to generate multiple cracking under loading. This composite is also known as Engineered Cementitious Composites (ECC), which was first developed by Professor Victor Li at the University of Michigan, in the United States. Over the last five years, the Laboratory of Testings and Structural Models (LEME) of UFRGS has developed a research area aiming to adapt ECC with local materials. In this context, polypropylene fibers were used to substitute PVA fibers and rice husk ash was used to partially replace cement, aiming to develop more cost attractive and greener mixtures. This study analyzed the use of non-processed rice husk ash (grinded in laboratory for 1, 2, 4, 6 and 8 hours) as a pozzolanic material by means of x-ray diffraction tests, x-ray fluorescence, fire loss, performance index, specific mass and particle size distribution. This study characterized, in terms of mechanical behavior, the high strain cementitious composites with 10%, 20% and 30% (by volume) of non-processed rice husk ash as cement replacement. The experimental tests were carried out in terms of direct tensile and four points bending tests. Aiming to obtain a first indication of durability, absorption and void rate tests were performed. Other tests were performed to obtain the hydration heat curve aiming to determine a possible retarding effect that the rice husk ash may cause to the composite. Finally, in order to analyze the use of the composite as a reinforcement material, tests were carried out to obtain the bond behavior in terms of oblique shear and pullout methods. The reflection of cracks was also evaluated along with scanning electron microscopy of the composites. The results were satisfactory for composites with 30% of rice husk ashes grinded for 8 and 4 hours, presenting good results in terms of ductility and resistance to crack propagation.