Thesis(M.S.)--Auburn University, 2005. / Abstract. Vita. Includes bibliographic references.

Resumo: O uso do concreto na elaboração de estruturas de concreto armado está ligado à capacidade das mesmas em resistir aos esforços solicitantes, por meio da aderência que existe entre os materiais aço e concreto. Considerando-se que a maioria dos concretos à base de cimento apresenta uma pequena resistência à tração, se comparada à compressão, algumas alternativas para melhorar o seu comportamento em relação a esse aspecto vem sendo estudadas com sucesso, como, por exemplo, a adição de diversos tipos de fibras. Em outro contexto, a incorporação de resíduos no concreto surge como uma possibilidade para se atenuar impactos ambientais. Um exemplo desses resíduos é o de borracha de pneu, gerado em abundância durante o processo de recauchutagem. Observa-se, no entanto, que a inclusão desse resíduo pode provocar uma diminuição da resistência e do módulo de deformação longitudinal. Atualmente, em muitos casos, a utilização de lajes treliçadas têm sido mais vantajosa que o uso de lajes maciças, tanto do ponto de vista de execução, como do ponto de vista econômico. Para as situações de pequenos e médios vãos, e para cargas não muito elevadas, é possível que as lajes treliçadas não tenham o seu desempenho estrutural muito prejudicado em função da incorporação da borracha no concreto, uma vez que a limitação de sua capacidade resistente não seria dada pelo esmagamento do concreto mas sim pelo alongamento excessivo da armadura. Sendo assim, este trabalho tem como objetivo a utilização de resíduos de borracha em substituição parcial dos agregados do concreto que compõem a capa e as vigotas de lajes pré-fabricadas treliçadas unidirecionais. No total, foram ensaiados seis modelos, sendo três deles sem adição de borracha e os outros três com substituição de 10% do volume de areia por resíduo. Os modelos de lajes foram instrumentados... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The use of concrete in the manufacture of reinforced concrete structures is related to the ability of this material to resist the loads by the bond that exists between the reinforcement and the concrete. Considering that most of the cement-based concrete has a small tensile strength when compared to compression, some alternatives to improve their behavior in relation to this aspect has been studied successfully, as the addition of several types of fibers, for example. In another context, the incorporation of residues in the concrete emerges as a possibility of attenuating the environment impacts. An example is the tire rubber residue, generated in abundance during the retreading process; however, it is noted that the inclusion of this residue can cause a decrease in the compressive strength and in the module of elasticity. Currently, in many cases, the use of lattice slabs is more advantageous than the use of solid slabs, both in terms of execution, as the economic point of view. For small and medium spans, and for not high loads, it is possible that lattice slabs do not present a bad performance due to the incorporation of rubber into concrete since the limitation of its strength capacity would not be given by the concrete crushing but by the excessive reinforcement strain. Therefore, this work aims to use rubber tire residue as an aggregate in the concrete of the cover and in the concrete of the joist of the lattice precast unidirectional slabs. The residue partially replaced the fine aggregate. In total, six models were tested, being three of them without the rubber addition and the other three with replacement of 10% in the volume of sand per residue. The models were instrumented and tested for flexure at 28 days old, and the vertical displacements, the strains in concrete and in the reinforcement were recorded. The cracking... (Complete abstract click electronic access below) / Orientador: Jorge Luís Akasaki / Coorientador: José Luiz Pinheiro Melges / Banca: Haroldo de Mayo Bernardes / Banca: Guilherme Sales Soares de Azevedo Melo / Mestre

abstract: Natural rubber and rubber products can be produced from the guayule plant (Parthenium argentatum Gray), which is a low input perennial shrub native to Mexico and the American Southwest. Guayule rubber has the potential to replace Hevea (Hevea brasiliensis) rubber, the most common natural rubber, and synthetic rubber, which is derived from petroleum, in a wide variety of products, including automobile tires. Rubbers make up approximately 47% of the analyzed conventional passenger tire's weight, with 31% from synthetic rubber and 16% from natural Hevea rubber. Replacing the current rubber sources used for the tire industry with guayule rubber could help reduce dependency on imported rubber in addition to reducing greenhouse gas emissions. Moreover, residues from guayule rubber are being researched as a bioenergy feedstock to further improve the environmental footprint of guayule rubber products. This study used life cycle assessment (LCA), a useful tool to determine environmental impacts from a product or process, to quantify and compare environmental impacts of the raw material extraction, transportation and manufacturing of a conventional and a guayule rubber based passenger tire. The impact results of this comparative LCA identified the major environmental impacts and contributing process and informed how the impacts from the tire production can be reduced through utilization of natural rubber co-products as electricity off-sets and reducing guayule rubber's environmental impacts through agricultural and transportation modifications. Results showed that tire raw material extraction contributed the majority of impacts in all categories, where the production of guayule rubber for guayule tires, and the production of synthetic rubber for conventional tires, were the main contributors. Guayule rubber impacts occurred mainly from electricity consumption for agricultural irrigation, while synthetic rubber is a petroleum-based material resulting in high impacts. Transportation impacts had little significance compared to other stages in the life cycle, except for smog impacts, which occurred mainly from truck transport for guayule tires, and transoceanic transport for conventional tires. Tire manufacturing impacts occurred mainly from electricity use in the facilities and were reduced with the use of guayule rubber in guayule tires. / Dissertation/Thesis / M.S. Civil and Environmental Engineering 2014

The research problem addressed in this study was aimed in assisting the management of Bridgestone/Firestone, Port Elizabeth plant, in selecting an appropriate process for the formulation of an operations strategy. The author embarked on a literature survey to gain understanding of the challenges that are occurring in the market environment. The theories and techniques around operational strategies were extensively researched in an effort to effectively and efficiently assist the management of Firestone in achieving a competitive advantage over rival competitors. Other areas of focus include the content, development, principles and concepts in developing an operations strategy. The author details the process of the formulation of an operations strategy as well as the discussion of four models/procedures deployed in organisations that would enhance strategy formulation. It is evident from the findings of the empirical study that a high percentage of the respondents “agree” that the strategy deployed within Bridgestone/Firestone, Port Elizabeth plant is appropriate, yet an alarmingly high percentage believe it to be “ineffective.

The main aim of this diploma thesis is to deal with the influence of tire properties and parameters of driving dynamics. In the introduction are discussed the driving dynamics of vehicles and the importance of tires and their construction. The second part is devoted to implementation and evaluation of the own experiment. My experiment is to test the braking tire inflation and condition of various different sizes. The conclusion summarizes the importance of proper tire condition.

The key goal of the following diploma thesis is to evaluate influence of the air pressure in the car tires on the driving dynamic, stability and comfort. The first part is dedicated to the theory of the driving dynamic, stability, tire parameters and tire inflation. Next practical part is focused on the drivers’ knowledge about the correct tire inflation and follows with the measurements and evaluation of the influence of the tire inflation on the driving characteristics, riding comfort and its comparison. These influences are summarized and followed up by the recommendations for the drivers and also the expert activities.

In an effort to reduce physical testing during the development process of a new vehicle, the automotive industries develop methods that can facilitate the recreation of the physical testing scenarios in virtual environments using simulation software. This thesis aims to develop a method which would help evaluate the vehicle’s dynamic properties without it being subjected to physical testing. The goal is to develop a tool that can be used in an early development phase by the industry and that would allow for modifications and calibration to take place. A vehicle model as well as an electronic stability control implementation is built, and the model’s performance to an ISO3888 part-2 double lane change test is evaluated. Since the handling potentials of the vehicle are rated by its entry speed in that test, the model was subjected to an optimization process where its steering action was controlled in order to achieve the highest possible entry speed to the test in an effort to isolate the vehicle’s dynamic potential from the influence of a human driver when conducting this test. The vehicle modelling procedure is done in steps, from a simple implementation of a linear bicycle model to a more complex implementation of a four-wheel vehicle including roll, tire relaxation and suspension compliance properties as well as a simplified ESC implementation. The results of the steering input optimization process were physically tested on a test track, where the correspondence of the model to the real vehicle was evaluated. By further promoting the vehicle dynamics modelling, this tool can facilitate study more testing scenarios and options and it can serve as a step toward the reduction of the physical testing when the vehicle’s dynamic and handling performance need to be studied and evaluated. / Under utvecklingsprocessen av nya fordon sker en strävan mot att reducera fysiska tester, bilindustrier utvecklar därför metoder för att återskapa fysiska testscenarier i virtuella miljöer med hjälp av simuleringsmjukvara. Denna studie har som målsättning att utveckla en metod, med vilken fordonets dynamiska egenskaper kan utvärderas utan att utföra fysiska tester. Målet är att utveckla ett simuleringsverktyg som, i en tidig utvecklingsfas, kan användas av fordonsindustrin och som skulle införa både modifikations- och kalibreringsmöjligheter i detta skede. Såväl en fordonsmodell som ett anti-sladd system är konstruerat och modellens prestanda i ett dubbelt filbyte, specificerat i ISO3888 del 2, är utvärderad. Då bilens dynamiska prestanda klassificeras utifrån ingångshastigheten i detta test utfördes en optimeringsprocess där hjulens styrvinklar reglerades för att uppnå högsta möjliga hastighet vid testets startposition, detta för att separera fordonets dynamiska klassificering från mänsklig inverkan. Processen att konstruera fordonsmodellen utfördes med succesivt ökande antal av fordonsegenskaper, från en enkel implementering av en linjär cykel-modell till en tvåspårs-modell med krängning, transienta däckegenskaper, hjulupphängningsegenskaper samt ett anti-sladd system. Resultatet av den optimerade styrregleringen testades i motsvarande fordon på en testbana varefter modellen kunde utvärderas med det verkliga testet som referens. Genom en utökad möjlighet till simulering kan detta verktyg ge möjligheten att studera fler scenarier såväl som alternativa modelleringskonfigurationer; det kan reducera fysiska tester då fordons dynamiska prestanda ska klassificeras, studeras samt utvärderas.

Used tires have the potential for becoming popular in pollution control media used in stormwater applications including pervious pavement sub bases, green roof growth media, and upflow filters. Using tire crumb to decrease nutrients can minimize impacts on ecology while reducing the human footprint left by used tires. However, if tire crumb is not examined for toxicity, the ecological balance could unknowingly be disrupted. This research tested the acute toxicity of tire crumb in aquatic systems by finding the Lethal Concentration for 50% kill (LC50). Using an extreme tire crumb load, P. promelas (fathead minnow) were exposed to leachates created with tire crumb and several different types of water including distilled water, tap water, and detention pond water. For distilled and tap water, the addition of tire crumb increased the survival of P. promelas. For detention pond water, the addition of tire crumb decreased the survival of P. promelas, though only enough to find an LC50 for detention pond water influenced immediately by stormwater runoff. An LC50 was found when 100 percent tire crumb filtrate is prepared with 25 grams of tire crumb per liter of detention pond water collected directly after a storm. The LC50 found is resultant of a tire crumb load significantly higher than what can be expected in the environment. Based on this research, tire crumb is considered non-threatening to aquatic fish and safe to use with detention pond water.

Predicting tire performance on soft, fine-grained soils is required for many off-road explorations in the military, mining, agricultural, and earth-moving sectors. However, the mobility in deformable material is extremely challenging, especially in the presence of water. Although there is a significant amount of research on terrains such as sands, there is a lack of research on fine-grained soils. This research is part of a bigger project that presents a novel approach to improve the mobility of off-road vehicles on wet deformable soils. The approach integrates experimental data from small-scale soil testing, large-scale soil-tire interaction testing, and advanced physics-based numerical simulation techniques. In particular, this thesis attempts to characterize the clay-tire interface by conducting large-scale direct shear tests. In addition to clay-tire contact friction, the properties and strength parameters of the soft clay are determined by conducting various index properties and advanced tests. The testing program accounts for different stresses, loading conditions, and boundary conditions, decided taking into account real field conditions. The results from all these experiments will be used to calibrate and validate the material constitutive models required for the development of a mobility predictive numerical model. Overall, this study contributes to the development of more advanced and accurate terramechanics models that involve deformable terrains like soft clays. / Master of Science / The prediction of Vehicle mobility on soft, fine-grained soils is challenging due to the impact of soil behavior on mobility, which is not taken into account by traditional vehicle simulation software. However, as off-road exploration and resource extraction become increasingly important, particularly in military, agricultural, and earth-moving sectors, the study of vehicle mobility on deformable soils is inevitable. The difficulty in predicting tire performance on soft, fine-grained soils is due to the lack of proper experimental data and numerical modeling techniques that accurately characterize the interaction between soil and vehicle tires, known as "terramechanics." The study forms a constituent part of a broader project, which aims to integrate the experimental research data from small-scale soil testing, large-scale soil-tire interaction testing, and advanced physics-based numerical simulation techniques. The main contribution of this study is to investigate soil-tire interaction to determine the contact friction between the soil and tire by conducting large-scale direct shear tests. It also involves conducting basic index properties tests and advanced shear strength and compression tests. The results from all these tests contribute to developing more accurate soil-tire interaction models in terramechanics. Given the scarcity of research on large deformable terrains like soft clays, this study can make a significant contribution towards developing more advanced and accurate terramechanics models that involve deformable terrain, which can be useful in various applications.

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