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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
191

Da avaliação de equipamentos para drenar a qualidade de viagens por rodovias / From drainage equipments to trip quality in rural highways

Josiane Palma 15 December 2000 (has links)
Este trabalho relata e discute resultados obtidos em tentativa para mostrar que a distribuição de notas atribuídas às viagens por segmentos de rodovias, o formato da seção transversal e medidas sobre variáveis que classifiquem o estado ou funcionamento de equipamentos para drenar água de chuva, podem classificar e identificar informações que contribuam na manutenção ou construção de componentes de vias. Estas informações podem tornar possíveis melhorias nos serviços prestados pela superfície de pavimentos ao tráfego de veículos, e, por conseqüência, na qualidade de viagens por rodovias. O processo usado foi identificar e quantificar índices que expressam medidas de solicitação em equipamentos para drenar. O manuseio e análise ele dados adotaram métodos estatísticos para obter parâmetros de conseqüências de obras ou assemelhados que alterem a condução de água. O estudo de caso, usado para obtenção de argumentos que orientaram o trabalho, adotou um conjunto ele rodovias vicinais, localizado próximo à Araraquara, estado ele São Paulo, onde um grupo de pesquisadores levantou dados e analisou qualidade de viagens, pavimentos, geometria e drenagem. / It is related and discussed the results from actions in an attempt to show that the scores to trips on highways, the format of the cross section of highways and surveys on variables that classify drainage equipments can be used to classify information that contributes to maintenance and construction decisions. Measures on variables to explain the state of drainage equipments was taking into account. The variable used to explain the behavior of pavements and quality of trips was the distribution of scores attributed to the highway segments trips by a group of trained appraisers. The statistical technique used to analyze the data was the multiple linear step-by-step regressions. lt is told the application results to a case study on a set of local highway segments near the city of Araraquara, State of Sao Paulo.
192

Estudo laboratorial acerca da possibilidade de aproveitamento da cinza pesada de termelétrica em bases e sub-bases de pavimentos flexíveis / Laboratory study concerning the possible utilization of the bottom ash from thermal power station in the bases and sub-bases of pavements

Rodrigo Pires Leandro 17 October 2005 (has links)
A cinza pesada é um sub-produto gerado do processo da queima do carvão mineral pulverizado nas caldeiras das termelétricas para a produção de vapor aquecido que atuará na geração de energia elétrica. Não há um destino adequado para esse tipo de cinza, sendo que o volume gerado diariamente é depositado em bacias de sedimentação, causando, dessa forma, problemas ambientais. Principalmente nos Estados Unidos, muitas pesquisas têm evidenciado o sucesso do emprego deste resíduo na construção de rodovias. Contudo, no Brasil as pesquisas sobre cinza pesada estão mais voltadas para a área de edificações. Deste modo, a proposta da pesquisa foi investigar os efeitos da cinza pesada quando incorporada a solos, através de ensaios laboratoriais, visando o aproveitamento deste resíduo na construção de bases e sub-bases de pavimentos. Também foi avaliado o efeito da adição de cal às misturas solo-cinza. Os ensaios utilizados na etapa experimental foram os de mini-CBR, resistência à compressão simples e resistência à tração por compressão diametral. Complementarmente, realizaram-se ensaios de CBR e de resistência à compressão simples na condição imersa. Os resultados mostraram que as adições de cinza pesada aos solos não melhoram as propriedades mecânicas das misturas compactadas. Entretanto, a adição de 3% de cal às misturas de solo-cinza proporciona a melhora significativa no comportamento mecânico das misturas, oferecendo uma solução para aproveitamento da cinza pesada na construção rodoviária. / Bottom ash is a by-product from the burning of mineral coal. It is utilized as fuel in thermal power stations in order to produce electrical energy. The bottom ashes are deposited in the lagoons and are harmful to the environment. In the United States, several researches have indicated successful uses of this waste in the construction of roadways. However, in Brazil the researches have been accomplished to use the bottom ashes in the civil construction. Thus, the purpose of the present research was to investigate the results of the bottom ash additions to soil in order to utilization in bases and sub-bases of pavements. Afterward, the effects of lime additions to soil-bottom ash mixtures were evaluates. The tests employded were mini-CBR, unconfined compressive strength and indirect tensile strength. California bearing ratio and immersion unconfined compressive strength were accomplish such supplementary tests. The results indicated that bottom ash additions to soils does not improve the mechanical properties of the compacted mixtures. However, the addition of the 3% of the lime to soil-bottom ash mixtures provided better mechanical performance, offering a feasible solution for the use of this waste in road construction.
193

Séries temporais e estudos sobre comportamento de pavimentos / Contribution to pavement performance modelling

Glauco Pontes Filho 03 May 1999 (has links)
Esse trabalho relata e discute resultados obtidos em uma tentativa para mostrar que séries temporais podem ser úteis e eficientes para identificar informações sobre características de comportamento de pavimento ao longo do tempo em que é submetido às solicitações de cargas provenientes de tráfego de eixos de veículos. Os dados e informações utilizadas foram obtidas por observações sobre o comportamento de um trecho experimental de via que liga o trevo de Assaí a Pau D\'Alho, no nordeste do estado do Paraná. Os dados foram manuseados em computador através do método para busca de funções para estimativa de valores de elementos de séries temporais \"Autoregressive lntegrated Moving Average\" para obter informações sobre o comportamento de índice para expressar o \"estado de pavimento\". / The results obtained on trying to show that time series should be useful and efficient in identifying information on the behavior of pavements submitted to vehicle axle load traffic were reported and discussed. The data and inputs used were obtained from observing the experimental road segment Assai to Pau D\'Alho in Northeast of Parana State (Brazil). The data were processed in computers using the \"Autoregressive lntegrated Moving Average\" method to search for estimating values functions for components of time series and obtain information on a pavement performance index.
194

Avaliação do efeito de restaurações com fresagem e recapeamento nas condições funcional e estrutural de pavimentos com volume de tráfego médio / Evaluation of the effects of a milling and asphalt concrete substitution on the functional and structural conditions of medium-traffic roads pavements

Echeverria, José Antonio Santana January 2011 (has links)
Nesta dissertação foi analisado o efeito de restaurações com fresagem e recapeamento com concreto asfáltico nos parâmetros funcionais e estruturais em dois segmentos de rodovias federais de tráfego médio da região noroeste do Estado do Rio Grande do Sul. Ambos os segmentos estão inseridos na unidade geomorfológica denominada Planalto Meridional, e possuem subleito classificado pedologicamente como latossolo vermelho. Na condição funcional foram avaliados: o Índice de Gravidade Global (IGG), macrotextura e a irregularidade longitudinal (IRI). Na condição estrutural foram realizadas avaliações destrutivas: umidade e massa específica aparente seca em campo das camadas inferiores do pavimento, e como avaliação não-destrutiva, medidas de deflexão com viga Benkelman. Com os materiais coletados foram realizados ensaios laboratoriais de compactação e teor de umidade, ISC, equivalente de areia, limites de Atterberg e ensaios triaxiais de carga repetida para obtenção de modelos de módulo de resiliência. De posse dos dados citados, aplicaram-se modelos de previsão de desempenho para estimar as reduções de Irregularidade e da Deflexão e compará-las com valores resultantes de medidas antes e depois da restauração. Por meio de análises estatísticas, foi obtida uma linha de tendência para redução de deflexão com restauração simples, aplicável, em princípio a pavimentos semelhantes na região em estudo. Ainda, comparam-se valores de ATR (afundamento na trilha de roda) medidos com perfilômetro laser e treliça metálica, observando-se a discrepância significativa entre os resultados. Globalmente, verificou-se que a solução de restauração restituiu aos pavimentos a capacidade estrutural adequada, melhorando também sua condição funcional, em termos de conforto e a segurança viária. / This Dissertation reports the main findings of a research on the effects of a basic rehabilitation procedure (milling and replacing the distressed asphalt wearing course by a new layer of asphalt concrete) on functional and structural parameters of two test sections of medium-traffic roads in the Northwestern Region of Rio Grande do Sul State, Brazil. Both test sections are placed in a Geomorphological Unit called “Planalto Meridional” (South Plain) and subgrade soils are pedologycally classified as red latosols. Regarding the pavements functional condition, the following parameters were evaluated: roughness (IRI – International Roughness Index), macrotexture and a Brazilian Global Severity Index (IGG – “Indice de Gravidade Global”), which is computed considering the severity and the frequency of a set of pavement distresses. In order to evaluate the pavements structural capacity, trenches were opened, in situ moisture content and dry density of base, sub-base and subgrades were measured and materials were sampled in order to carry out laboratory tests. Surface deflections were measured using a Benkelman Beam. Roughness and deflections were measured before and after rehabilitation, while macrotexture was measured on the new asphalt layer. Laboratory procedures consisted of gradation, Atterberg Limits, compaction, CBR and resilient modulus tests; the Sand Equivalents of base and sub-base aggregates were also determined. Pavement Prediction Models were used to estimate roughness and deflection decreases due to the rehabilitation procedure; these estimations were compared to the differences between roughness or deflection before and after rehabilitation. By means of Statistics analysis, a tendency line that allows estimating deflection reduction due to the rehabilitation procedure was defined. That tendency line might be used to estimate deflection reduction in similar pavements of the Northwestern Region of the state. Rut depth values measured with a three-point ruler were compared to values measured with a laser profiler; it was shown that both sets of values are quite different. All in all, it was verified that the rehabilitation procedure (milling and replacing the distressed asphalt wearing course by a new layer of asphalt concrete) provided the studied pavements adequate bearing capacity and improved their serviceability (parameter related to safety and confort).
195

Energy Dissipation Caused by Asphalt Roadway Gouges for Use in Accident Reconstruction

Crosby, Charles L. 14 December 2009 (has links)
In reconstruction of on-roadway vehicle accidents, roadway surface gouges and the forces and energy attributed to the related vehicle components become important keys to resolving an accurate accident reconstruction. These roadway gouge forces vary depending upon such factors as surface temperature and the velocity and geometry of the gouging mechanism. Accounting for the forces applied to vehicle components and the energy dissipated from such forces can be helpful in accident reconstruction where supporting data exists. This research documents the force necessary to create a given roadway gouge geometry. Controlled pavement gouging tests were performed using roadway surface temperature and gouging velocity as main factors. The results of this testing and analysis are useful in quantifying gouge forces and energies for use in accident reconstruction. The findings show that the temperature of the roadway surface that is being damaged significantly affects the amount of force required to cause the damage. A summary of experiments and techniques as applied to accident reconstruction are presented.
196

Fractionation of recycled asphalt pavement materials: improvement of volumetric mix design driteria for High-RAP content surface mixtures

Shannon, Cory Patrick 01 July 2012 (has links)
The objective of this research is to examine the effects that different methods of RAP stockpile fractionation have on the volumetric mix design properties for high-RAP content surface mixes, with the goal of meeting all specified criteria for standard HMA mix designs. The processing of RAP materials results in the degradation of the aggregate structure of the original pavement. The increased presence of fine RAP materials in the stockpile can be attributed to the amount of crushing done on the RAP millings. Fractionation methods were designed to separate the stockpile at certain sizes to isolate the fine RAP materials which contained higher amounts of fine aggregate and negatively impacted the volumetric properties of the mix design. These isolated RAP materials were used in reduced proportions or completely eliminated, thereby decreasing the amount of fine aggregate material introduced to the mix. Mix designs were created using RAP materials included from each original stockpile and the two fractionated stockpiles created from each original stockpile at high-RAP contents of 30%, 40% and 50% by virgin binder replacement. Fractionation of RAP materials was effective in improving the volumetric properties of high-RAP content mixtures through reduction of fine aggregate material introduced by the RAP materials.
197

An Analysis of Sensitivity in Economic Forecasting for Pavement Management Systems

Fuentes, Antonio 01 May 2015 (has links)
The research presented in this thesis investigates the effect the data collection process has on the results of the economic analysis in pavement management systems. The incorporation of pavement management systems into software packages has enabled local governments to easily implement and maintain an asset management plan. However a general standard has yet to be set, enabling local governments to select from several methods of data collection. In this research, two pavement management system software packages with different data collection methods are analyzed on the common estimated recommended M&R cost provided by their respective economic analysis. The Transportation Asset Management Software (TAMS) software package developed by the Utah LTAP Center at Utah State University consists of a data collection process composed of nine asphalt pavement distress observations. The Micro PAVERTM software package developed by the Army Corps of Engineers consists of a data collection process composed of 20 asphalt pavement distress observations. A Latin-hypercube sample set was input into each software package, as well as actual local government pavement condition data for the City of Smithfield, Utah and the City of Tremonton, Utah. This resulted in six total data sets for analysis, three entered and analyzed in TAMS and three entered and analyzed in Micro PAVERTM. These sample sets were then statistically modeled to determine the effect each distress variable had on the response produced by the economic analysis of estimated recommended M&R costs. Due to the different methodologies of pavement condition data collection, two different statistical approaches were utilized during the sensitivity analysis. The TAMS data sets consisted of a general linear regression model, while the Micro PAVERTM data sets consisted of an analysis of covariance model. It was determined that each data set had varying results in terms of sensitive pavement distresses; however the common sensitive distress in all of the data sets was that of alligator cracking/fatigue. This research also investigates the possibility of utilizing statistically produced models as a direct cost estimator given pavement condition data.
198

Evaluation of Digital Imaging Systems Used in Highway Applications

Mraz, Alex 21 July 2004 (has links)
Manual pavement condition surveys are gradually replaced by more comprehensive automated surveys conducted by multi-function highway evaluation vehicles. Highway evaluation vehicles are generally equipped with laser profiling, land navigation, and imaging sub-systems. The imaging system consists of three cameras; forward-view and side-view digital area-scan cameras for capturing images of traffic signs and right-of-way safety features, and a pavement digital line-scan or area-scan camera for capturing images of the pavement surface. In addition to the 3-laser and accelerometer-based profiling system, these vehicles are also equipped with differential global positioning equipment (DGPS) and an inertial measurement unit (IMU) for cross-slope, curvature and grade measurements. Digital imaging systems installed in automated highway evaluation vehicles are generally designed on modular basis where subsystems by different manufacturers are assembled to customize the system and fulfill the users' needs while minimizing the cost. In most such cases, manufacturers' specifications for a subsystem would not be reliable with respect to the eventual performance of that subsystem as part of the entire assembly. On the other hand, no guidelines are available for performance evaluation of imaging systems as assemblies of discrete subsystems. Moreover, images acquired by digital cameras can become contaminated by random noise affecting their quality and the ability of identifying important features. These issues have surfaced during the development and testing of the Florida Department of Transportation (FDOT) highway evaluation vehicle. This first phase of the work involved in this dissertation research concerns the study of basic criteria for evaluation of image quality through measurement of well-defined properties of images such as color reproduction, tone reproduction, detail reproduction, as well as the levels of noise, and optical distortion. Standard and reliable methods that can be adopted for evaluation of the above properties are discussed first. Then, by applying the above evaluation criteria to the imaging systems of the FDOT highway evaluation vehicle, it is shown how the sources of images sub-quality can be recognized and the optimum settings achieved. The second phase of the dissertation research is focused on the investigation of the sources of noise that can affect the digital line-scan distress images. As a result of this study, a novel technique was developed to filter out noise present in pavement distress images by using intensity measurement obtained from a standard grayscale target. In addition, a detailed experimental study was conducted to investigate the effect of the speed of evaluation and lighting conditions on the accuracy and repeatability of digital line-scan images in representing the actual distress condition of a pavement. The conclusions drawn from the second phase can be used to minimize the effect of noise on digital images of pavement distress and to improve the accuracy of evaluation of pavement cracks based on digital images. Hence the results of this study will certainly enhance the overall efficiency of the automated evaluation of pavement distress and highway features.
199

A laboratory scale study of infiltration from Pervious Pavements

Zhang, Jie, s3069216@student.rmit.edu.au January 2006 (has links)
Increased urbanization causes pervious greenfields to be converted to impervious areas increasing stormwater runoff. Most of the urban floods occur because existing drainage systems are unable to handle peak flows during rainfall events. During a storm event, flood runoff will carry contaminants to receiving waters such as rivers and creeks. Engineers and scientists have combined their knowledge to introduce innovative thinking to manage the quality of urban runoff and harvest stormwater for productive purposes. The introduction of pervious pavements addresses all the principles in Water Sensitive Urban Design. A pervious pavement is a load bearing pavement structure that is permeable to water. The pervious layer sits on the top of a reservoir storage layer. Pervious pavements reduce the flood peak as well as improve the quality of stormwater at source before it is transported to receiving waters or reused productively. To be accepted as a viable solution, understanding of the influence of design parameters on the infiltration rate (both from the bedding and the sub-base) as well as strength of the pavement requires to be established. The design of a particular pavement will need to be customized for different properties of sub layer materials present in different sites. In addition, the designs will have to meet local government stormwater discharge standards. The design of drainage systems underneath pervious pavements will need to be based on the permeability of the whole pervious system. The objectives of the research project are to: • Understand the factors influencing infiltration capacities and percolation rates through the pervious surface as well as the whole pavement structure including the bedding and the sub-base using a laboratory experimental setup. • Obtain relationships between rainfall intensity, infiltration rate and runoff quantity based on the sub-grade material using a computational model to assist the design of pervious pavements. A laboratory scale pavement was constructed to develop relationships between the surface runoff and the infiltration volume from a pervious pavement with an Eco-Pavement surface. 2 to 5mm crushed gravel and 5 to 20mm open graded gravel were chosen as the bedding and sub-base material. Initial tests such as dry and wet density, crushing values, hydraulic conductivity, California Bearing Ratio tests for aggregate material were conducted before designing and constructing the pavement model. A rainfall simulator with evenly spaced 24 sprays was set up above the pervious pavement surface. The thesis presents design aspects of the laboratory scale pavement and the tests carried out in designing the pavement and the experimental procedure. The Green and Ampt model parameters to calculate infiltration were obtained from the laboratory test results from aggregate properties. Runoff results obtained from rainfall simulator tests were compared with the Green and Ampt infiltration model results to demonstrate that the Green and Ampt parameters could be successfully calculated from aggregate properties. The final infiltration rate and the cumulative infiltration volume of water were independent of the rainfall intensity once the surface is saturated. The model parameters were shown to be insensitive to the final infiltration capacity and to the total amount of infiltrated water. The Green and Ampt infiltration parameters are the most important parameters in designing pervious pavements using the PCSWMMPP model. The PCSWMMPP model is a Canadian model built specially for designing pervious pavements. This is independent of the type of sub-grade (sand or clay) determining whether the water is diverted to the urban drainage system (clay sub-grade) or deep percolation into the groundwater system (sand sub-grade). The percolation parameter in Darcy's law is important only if the infiltrated water recharges the groundwater. However, this parameter is also insensitive to the final discharge through the subgrade to the groundwater. The study concludes by presenting the design characteristics influencing runoff from a pervious pavement depending on the rainfall intensity, pavement structure and sub-grade material and a step-by step actions to follow in the design.
200

Effect of pervious and impervious pavement on the rhizosphere of American Sweetgum (Liquidambar styraciflua)

Viswanathan, Bhavana 2010 May 1900 (has links)
Mature trees help to offset urban area problems caused by impervious pavement. Trees in paved areas remain unhealthy due to a poor root zone environment. The objective of this experiment was to test if soil under pervious concrete, with greater water and gas infiltration, would be more beneficial to existing mature trees during urban development. Root activity, root growth and soil chemistry of American sweetgum under standard concrete, pervious concrete and no concrete were measured. Soil CO2 efflux rates and soil CO2 concentrations were extremely high under both concrete treatments. Soil under standard concrete had lower oxygen concentrations than soil under pervious concrete and control treatments, particularly under wet conditions. There was no pavement effect on soil water content or soil chemistry. Under control treatment standing live root length was greater than under both concrete treatments. There were no major differences in soil conditions between impervious and pervious concrete treatments. The soil under the plots, a Ships clay, with very low permeability may have prevented soil water infiltration. Likely this overrode any potential treatment effects due to porosity of the concrete. To obtain root zone benefits out of pervious concrete, a different base soil with a higher permeability would be a better alternative.

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