For a pre-cast concrete manufacturing company to obtain a Botswana Bureau of Standards (BOBS) certification time, money and effort have to be spent and yet it is not known whether the consumers will use the BOBS certification as a buying decision factor. The Botswana Bureau of Standards certified pre-cast concrete manufacturing companies have to comply with rigorous inspections to ensure that standards are maintained. Competition in the concrete manufacturing industry is contested by certified companies and uncertified companies and yet the market is shared amongst these players. This dissertation will endeavour to analysis the effects of Botswana Bureau of Standards certification on buyer decision on pre-cast concrete products in Gaborone Botswana. Therefore, the research findings will establish whether BOBS certification can be used as marketing tool. A sample of forty was drawn from the population in Gaborone to represent the whole of Botswana. Date was collected using both semi-structured and structured questionnaires. Responses were sorted according to similarities and then interpreted. Results in this research indicated that BOB certification influences concrete consumers' decisions. It was also indicated that BOB certification is actually a marketing tool that sways positively concrete products buyers' decisions. Therefore, it was recommended that concrete manufacturers should exploit this marketing tool to gain a larger market share. Those concrete products manufacturers whose products are not certified should consider this marketing tool in their marketing strategy in order to remain competitive. BOBS must also launch a massive public awareness to popularise the use of the certification by the manufacturers. Lastly, It is recommended that the Botswana Government must continue supporting BOBS to improve quality standards in the country. / (MBA) North-West University, Mafikeng Campus, 2005

An alternative structural system for short span bridges is presented: a precast segmental double-T with external, unbonded post-tensioning tendons. Single-span designs from 20 to 45 m long show that the system can be implemented over a wide range of spans and that the system’s sensitivity to post-tensioning losses reported in previous literature can be reduced by aligning the prestressing force more concentrically. Designs for multi-span bridges using this system are presented using simply supported spans connected by thin flexible linking slabs made of ultra high-performance fibre-reinforced concrete and using sections made fully continuous over intermediate supports. A simplified method of geometry control is presented to facilitate the proper alignment of precast segments without the use of match casting. The precast segmental double-T bridge is compared to sixteen existing slab on girder bridges and found to be a competitive alternative in terms of material use, cost, construction schedule, and aesthetic merit.

An alternative structural system for short span bridges is presented: a precast segmental double-T with external, unbonded post-tensioning tendons. Single-span designs from 20 to 45 m long show that the system can be implemented over a wide range of spans and that the system’s sensitivity to post-tensioning losses reported in previous literature can be reduced by aligning the prestressing force more concentrically. Designs for multi-span bridges using this system are presented using simply supported spans connected by thin flexible linking slabs made of ultra high-performance fibre-reinforced concrete and using sections made fully continuous over intermediate supports. A simplified method of geometry control is presented to facilitate the proper alignment of precast segments without the use of match casting. The precast segmental double-T bridge is compared to sixteen existing slab on girder bridges and found to be a competitive alternative in terms of material use, cost, construction schedule, and aesthetic merit.

This thesis evaluates the use of High Strength Lightweight Concrete (HSLW) in bridge girders for the I-85 Ramp "B" Bridge crossing SR-34 in Cowetta County, Georgia. This bridge consisted of four spans; all girders were constructed using lightweight expanded slate aggregate. Spans 2 and 3 had a design strength of 10,000 psi, and span 2 was chosen for this research. The BT-54 girders were 107 ft 11½ inches in length. The prestressing strands used in these girders were 0.6 in diameter, grade 270, low relaxation strands. Material properties and member properties were tested. All 5 girders of span 2 were instrumented with vibrating wire strain gages at midspan, as well as with DEMEC inserts for transfer length measurements and with a deflection measurement system. Transfer length measurements found the transfer length of the girders to be 23% less than the values suggested by AASHTO and ACI equations. The deflection measurements showed 4.26 inches of camber at 56-days while the girders were stored at Standard Concrete Products. The camber measurements matched theoretical predictions within 5%. Mechanical property tests found the concrete to be within all design requirements. A stiffness, load test was performed on each of the 5 girders at Standard Concrete Products. The average stiffness value of 8.428 x 106 kip ft2 is recommend for use by GDOT engineers in designing the deck and road profile. This thesis discusses all short term findings from construction to the end of storage. A later report will address long term issues such as creep and shrinkage, as well as the performance of the girders as part of the bridge.

Thesis (Ph. D.)--University of Canterbury, 2006. / Typescript (photocopy). Includes bibliographical references. Also available via the World Wide Web.

This thesis investigates the behaviour of UHPC as a fill material for precast deck panels subjected to negative bending. Two full-scale test specimens were constructed. The transverse joints between the panels, the shear pockets, and the deck haunches were all filled with UHPC. A total of four tests were performed including two static tests to failure and two fatigue tests, one of which was performed to failure. Testing consisted of a loading apparatus acting upwards on the deck soffit in an attempt to impose tensile stresses across the transverse joints, representing the conditions that a transverse joint in the negative moment region of a continuous bridge deck would experience. It was concluded that the transverse UHPC joint performed satisfactorily by transferring bending stresses and shear stresses across the joint from one panel to the adjacent panel. Overall, the test specimens displayed performance levels expected from conventional cast-in-place concrete deck alternatives. / February 2016

Made available in DSpace on 2014-06-11T19:27:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-12Bitstream added on 2014-06-13T20:27:39Z : No. of bitstreams: 1 bertolucci_fs_me_ilha.pdf: 2860301 bytes, checksum: 3f3004f9d02861054ffe5fb10b1b2e7d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A indústria estruturas de concretos pré-moldados possui como grande preocupação a ligação entre seus elementos, tendo em vista que a mesma exerce grande influência no comportamento da estrutura, sendo responsável pela transmissão e redistribuição dos esforços na estrutura. A grande diferença entre estruturas pré-moldadas e estruturas de concreto moldadas “in loco” em relação ao seu comportamento estrutural está na ligação entre seus elementos. As ligações apresentam certa deformação quando solicitadas, recebendo na literatura técnica a denominação de ligações semi-rígidas. Dessa forma, buscou-se estudar todos os grautes existentes no mercado e desenvolver um compósito cimentício de fácil preparo e de baixo custo, do tipo calda de cimento e argamassa, que apresentasse características mecânicas similares aos grautes. Foram desenvolvidas duas caldas de cimento e uma argamassa, as quais foram submetidas juntamente com os grautes selecionados a ensaios específicos de propriedades adesão e aderência. Dentre as principais conclusões obtidas podem ser ressaltadas que a grande parte dos grautes possui problemas de fluidez dificultando o preenchimento total das ligações e sua aplicação. Em relação à aderência as duas caldas de cimento e a argamassa apresentaram comportamento semelhante indicando que há uma boa condição de aderência e, os grautes, devido à sua grande diferença de composição, tiveram comportamentos distintos / One of the concerns of the precast concrete industry is the connection among their different types of elements, in order that they strongly influence the behavior of the structural group, being responsible for the transmission and redistribution of the efforts in the structure. Among the differences between precast structures and concrete structures shaped “in loco” we have the concern about the structural behavior of the link between its elements. The links have shown some deformation when tested, receiving in the technical literature the name of semi-rigid connections. For that the concrete’s precast structure has the behavior of a monolithic structure it’s necessary the solidarization of the connection which is made by filling the vertical and horizontal niches with the aid of the grout. In this paper, we aimed to study some grouts of the Brazilian market and, at the same time, develop a cimentitius composite of easy prepare and low cost, of the cement paste and mortar types, with similar mechanical characteristics to industrialized grouts to be used in the filling of the precast structures. It was rheologically and mechanically created and evaluated two kinds of cement grout and one mortar composition that were submitted along with the selected grouts to an evaluation of their rheological behavior, and to specific tests of their mechanical properties of adhesion and bond. This study let us conclude that the cement paste and mortar developed showed a similar rheological behavior to the Herschel-Bulkley, besides to a good condition of bond and a good behavior in the structure link when compared to some industrialized grouts. Not all the evaluated grouts showed appropriate behaviors for joints’ filling

A necessidade de um nível básico de estabilidade nos fluxos de valor vem sendo enfatizada em diversos estudos, como um pré-requisito para a implantação sustentável de princípios e práticas da produção enxuta (PE). Na visão da PE, a estabilidade é multidimensional, devendo incluir todos os elementos de produção que sejam potenciais fontes de variabilidade excessiva. Nesse contexto, esta pesquisa propõe diretrizes para avaliar a estabilidade de um fluxo de valor sob a perspectiva da PE. Além disso, são propostos indicadores para a avaliação de um fluxo de valor de pré-fabricados para a construção civil. Para tanto, a pesquisa foi conduzida nas seguintes etapas: revisão bibliográfica; estudo de caso exploratório e estudo de caso. A pesquisa foi desenvolvida em uma empresa que produz peças de préfabricado de concreto, destinadas à construção civil. No estudo exploratório, foi possível identificar mecanismos para avaliar a estabilidade do fluxo de valor de uma família de produtos, considerando a estabilidade de mão-de-obra, materiais, máquinas e métodos (4M). No estudo de caso, os mecanismos de avaliação foram aplicados, re-interpretando dados já disponíveis na empresa e gerando novos dados, quando necessário. Com base nos resultados dos estudos de campo, bem como na revisão da literatura, foram identificadas cinco etapas para avaliação da estabilidade de um fluxo de valor: (a) desenvolver um mapa do fluxo de valor do estado (MFV) atual; (b) avaliar a estabilidade e a capacidade dos 4M em cada etapa do fluxo de valor; (c) desenvolver melhorias que contribuem para a estabilidade e capacidade; (d) representar as melhorias no MFV do estado futuro; (e) estabelecer um plano de ação para implantar o novo MFV. Vale salientar que, conforme explicitado nas etapas (b) e (c), a avaliação da estabilidade deve necessariamente ser acompanhada pela avaliação da capacidade, na medida em que não basta que os processos sejam estáveis se não atenderem às metas relativas aos clientes internos e externos. / The need for a basic level of stability in the value flow has been emphasized in several studies, as a prerequisite for the implementation of sustainable principles and practices of lean production (LP). In view of the lean production, the stability is multidimensional, and should include all the production elements that are excessive variability potential sources. In this context, this research proposes guidelines to evaluate the stability of a value flow from the perspective of lean production. Besides, indicators are proposed for the evaluation of a value stream of prefabricated materials for the building industry. With this aim, the research was conducted in the following steps: bibliographical review; exploratory study and study case. The collection of field data was developed in the company that produces pieces of concrete precast, destinated to for the building industry. In the exploratory study, it was possible to identify mechanisms to assess the stability of the value flow for one product family, considering the stability of manpower, materials, machines and methods (4M). In the case study, evaluation mechanisms were applied, re-interpreting the data already available in the company and creating new data when necessary. Based on field studies results, and literature review, there are identified five steps to evaluate the stability of a value flow: (a) to develop a value stream mapping of the current state (VSM); (b) to evaluate the 4M stability and capacity in each stage of the value flow; (c) to develop improvements that contribute to the stability and capacity, representing them in the VSM future state; (d) to establish an action plan to deploy the new VSM. It is also important to mention that, as explained in steps (b) and (c) the assessment of stability must necessarily be followed by the capacity assessment, because it is not enough that the processes are stable if they do not follow the internal and external customers’ targets.

In this work the connection behavior between precast elements using cement mortar with polypropylene fibers addition is studied to evaluate its performance when compression loads is applied. A numerical analysis with the finite elements program ANSYS 7.1® was made considering mortars range from 0% to 50% of polypropylene fibers addition. The numerical model considered in the analysis was composed of two reinforced concrete blocks with 10x10x20cm dimensions, joined between themselves by a cement mortar with marble and granite residue addition, developed in laboratory, which will receive polypropylene fibers addition. The numerical analysis was later validated by an experimental program. With the gotten results, it was evidenced that lower than 3% tax fibers propitiated better performance of the joint and, consequently, of the model. A profit in the horizontal and vertical deformation capacity was observed prorroguing the mortar splitting in the model, which makes high system strength capacity, resulting in an increase of the connection ductility. Between 4% and 10% the model kept any behavior alteration and from 15%, it started to lose strength and rigidity. The experimental models had presented load capacity profit with fibers addition and similar cracked ways of numerical model and the models observed in literature. However 2% fibers taxes higher were not possible to investigate because a lower workability performance had been gotten. / Fundação de Amparo a Pesquisa do Estado de Alagoas / Neste trabalho estuda-se o comportamento da ligação entre elementos pré-moldados através de juntas de argamassa com adição de fibras de polipropileno, avaliando o desempenho das mesmas quando solicitadas a tensões de compressão. O modelo proposto para análise do comportamento da ligação é composto de dois blocos de concreto armado com dimensões 10x10x20cm, unidos entre si por uma argamassa de cimento e areia com adição de resíduo oriundo do beneficiamento de mármore e granito, desenvolvida em laboratório em uma dissertação de mestrado, a qual recebeu adição de fibras de polipropileno. Faz-se uma avaliação numérica do modelo proposto através do programa de elementos finitos ANSYS 7.1® considerando argamassas com adição até 50% de fibras de polipropileno que é posteriormente validado em um programa experimental. Pelos dados obtidos numericamente, constata-se que o incremento de fibras até a taxa de 3% propicia um melhor desempenho da junta e, consequentemente, do modelo. Observa-se um ganho na capacidade de deformação horizontal e vertical da mesma, prorrogando, com isso, o descolamento do modelo, fazendo com que o sistema mantenha por mais tempo sua capacidade resistente, o que significa um aumento da ductilidade da ligação. Entre 4% e 10% o modelo mantém-se sem alteração no seu comportamento e a partir de 15%, começa a perder resistência e rigidez. Os modelos experimentais apresentam ganho de capacidade de carga com o acréscimo de fibras e modos de fissuração semelhantes ao modelo numérico e aos modelos propostos na literatura. Entretanto os teores práticos de fibras só atingem 2%, o que impossibilita os estudos para os demais teores.

Made available in DSpace on 2016-06-02T20:09:17Z (GMT). No. of bitstreams: 1 4584.pdf: 5769301 bytes, checksum: 2194ade756fb1c1f5f2cfe564e4a2c3d (MD5) Previous issue date: 2012-08-14 / This research is the systematization of the calculation and verification of a type of a very typical structural system of precast concrete in Brazil: the sheds. Through this research it is showed the main structural systems for this type of construction currently in use in Brazil. It also describes the component elements of these systems detailing the design techniques. Following it is a detailed the considerations of the actions over them and how to calculate the strain and displacement. With all previous data collected it is shown how the design is made with reinforcement of the roof s beam and how to guarantee that it meets with the relevant Brazilian standards. In the sequence, examples are made so that the reader can consolidate all the concepts involved in the previous sections. It shows the calculation and verification and finally points out the possibilities of improvement in some systems, detailing it. Finally, it highlights the points can still be studied to improve the design and the knowledge of sheds precast concrete. / Este trabalho trata da sistematização do cálculo e verificação de um tipo de sistema estrutural pré-fabricado em concreto com bastante uso no Brasil: os galpões com coberturas leves. Procura-se ao longo do trabalho mostrar os principais sistemas estruturais deste tipo de edificação usados no Brasil. Descreve-se também os elementos componentes destes sistemas com informações técnicas de projeto. Depois é feita uma análise detalhada das considerações das ações nos mesmos e como calcular os esforços solicitantes e deslocamentos. Com todos os dados anteriores levantados é mostrado como é feito o dimensionamento da armadura da viga de cobertura e como devem ser feitas as verificações para que as normas Brasileiras pertinentes possam ser atendidas. Finalmente, é feito um exemplo de maneira que o leitor possa consolidar todos os conceitos envolvidos no texto anterior. Mostra-se o cálculo e verificações e comenta-se as possibilidades de melhoria em alguns sistemas e detalhamento. Por fim são colocados os pontos que ainda podem ser estudados para melhorar o projeto e o conhecimento do funcionamento de galpões pré-fabricados de concreto.