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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.
91

Avaliação de pavimentos revestidos com tijolos / Brick pavement evaluation

Jairo Salim Pinheiro de Lima 28 September 1998 (has links)
Relatam-se atividades e resultados obtidos durante uma tentativa de \"mostrar que o estudo e adaptação de métodos clássicos de avaliação de pavimentos flexíveis pode identificar conceitos e informações que contribuam para desenvolver um arcabouço de métodos, conceitos e processos adequados para avaliar pavimentos cujo revestimento é construído com uso de tijolos\". Para isso: estudaram-se e analisaram-se métodos clássicos para avaliação de pavimentos, caracterizou-se um ambiente onde se usa pavimentos revestidos com tijolo cerâmico, Rio Branco, no Estado do Acre, Brasil, identificaram-se e caracterizaram-se defeitos físicos da superfície de pavimentos revestidos com tijolos que interferissem na qualidade de tráfego de veículos, estudaram-se processos de atribuição de notas a pavimentos por técnicos, motoristas e passageiros treinados para análise de qualidade de viagens pela superfície do pavimentos. A análise de regressão linear múltipla foi o procedimento usado para identificar relações entre notas atribuídas por avaliadores e distribuições de defeitos na superfície de pavimentos revestidos com tijolos. / lt was reported activities and results obtained when trying to show that the study and fitness of classical methods to evaluate flexible pavements should be good to identify information and concepts to contribute in developing method and processes to evaluate brick pavements. To do this: a) classical pavement evaluation was analyzed, b) an environment where brick pavements are constructed was described, the city of Rio Branco, State of Acre, Brazil, c) pavement surface defects were related to vehicle ride quality, d) Scores evaluation processes from drivers and passengers were studied. Linear multiple regression analysis was the method used to identify relationships among scores from evaluators and distributions of defects in brick pavement surface.
92

Qualidade de pavimentos e auditoria / Pavement quality and audit

Flávio Renato de Góes Padula 28 December 1999 (has links)
As Normas da Associação Brasileira de Normas Técnicas fixam conceitos e sugestões para a condução de auditorias sobre processos para produzir ou fornecer bens e serviços. Esse trabalho relata e discute informações obtidas durante ações de uma tentativa para \"mostrar que o uso de conceitos contidos nas Normas NBR ISO, série 10.000, pode contribuir para orientar análises sobre o comportamento de pavimentos e identificar diretrizes que contribuam para melhorar o nível para qualidade de construção, manutenção ou reabilitação destes equipamentos de rodovias\". / The Standards of the Associação Brasileira de Normas Técnicas fix concepts and suggestions to the conduction of auditing on processes to produce or to supply goods and services. This thesis reports and discusses information obtained during actions of an attempt \"to show that the use of concepts contained in Standards NBR ISO, series 10.000, can contribute to guide analyses on the pavement performance and to identify lines of direction that contribute to improve the level for quality of construction, maintenance or rehabilitation of these equipment of highways\".
93

Normas NBR ISO 9000 e qualidade de pavimentos / Standards NBR ISO 9000 and pavement quality

Claudia Scoton Antonio Marques 15 October 1999 (has links)
Mostrou-se por argumentação que a análise sobre conceitos e definições contidos nas Normas da Associação Brasileira de Normas Técnicas, série NBR ISO 9000, pode contribuir para identificar sugestões para estudos, análise e aceitação de ações para construção e manutenção de pavimentos, e comportamento de pavimentos durante as solicitações pelo tráfego de veículos do ponto de vista dos que usam rodovias. Para isso estudaram-se conceitos sobre qualidade e \"qualidade de pavimentos ou seus serviços\", conceituaram-se organizações, relataram-se e discutiram-se conceitos sobre \"sistema da qualidade\", \"garantia da qualidade\", manuseio de informações para ações sobre a qualidade; \"gestão da qualidade\", especificação e suas relações com clientes; qualidade de processos; qualidade de serviços. Por fim através de uma série de relatos sobre fatos discutiram-se a aplicabilidade de normas a estudos de qualidade de pavimentos, conclusões e sugestões. / Arguments were used to show that definitions and concepts from National Brazilian for Standards Association documents, the NBR ISO 9000, should contribute to identify concepts and suggestions to analyze and accept actions in construction and maintenance of pavements, or their performance using the user\'s point of view. lt was studied concepts on quality, pavement quality, organizations, quality systems, quality warranty, information to quality actions, actions on quality, process quality and service quality. After this it was reported some facts to guide the discussion on standard applications to pavement quality studies.
94

Mathematical prediction model of the infiltration deterioration due to clogging in pervious pavement based on pore/particle size distribution

Sharaby, Ahmed 03 April 2019 (has links)
Permeable pavement structures (PPSs) are one of the significant LID systems that have potential positive effect on the ecosystem. Yet, the performance of permeable pavements is still questionable. Further studies on the hydrological performance of the system need to be addressed for better design criteria and maintenance during the operation. The infiltration through the pavement is a crucial parameter that projects the system performance. Several factors affect its deterioration. The entrapment of suspended materials associated with the infiltrated stormwater through the system is one of the major factors that affect its performance. Factors that promote the entrapment of particles were discussed thoroughly through the literature and are explained in this study. Many previous studies were focused on performing experimental work and developing empirical models to study the hydraulic performance of the system. Yet, prediction models on the infiltration deterioration need to be addressed and theoretical analysis needs to be performed in order to determine the empirical coefficients with defined parameters that were introduced in the previous literature. Furthermore, the sensitivity of the pore and particle size distribution and mass loading rate of the suspended materials on the infiltration rate need to be addressed. The study focuses on investigating performance of PPSs with examining the variation effect of pore and particle size distribution on it. A prediction model was made and simulated using Matlab software, in which pore and particle size means and standard deviations are taken as inputs. Further, the variation in these parameters on infiltration is examined. Critical levels, that infiltration decline would reach, were defined based on the introduced mechanisms from the previous literature. Based on the variation of pore and particle size means and standard deviations, these critical levels were studied through the analysis of the obtained results from the simulated model. / Graduate / 2019-12-10
95

Automated crack control analysis for concrete pavement construction

Jang, Se Hoon 01 November 2005 (has links)
The focus of this research is on the control of random cracking in concrete paving by using sawcut notch locations in the early stages of construction. This is a major concern in concrete pavement construction. This research also addresses a probabilistic approach to determine the optimum time and depth of sawcutting for newly constructed portland cement concrete pavements. Variability in climate conditions and material characteristics during the hardening process affects the potential of cracking at any sawcut depth. Several factors affecting the probability of crack initiation are material strength parameters, method and quality of curing, slab/subbase stiffness, the amount and depth of steel reinforcement, friction between the slab and the subbase, and concrete shrinkage. Other factors relevant to concrete mixture characteristics such as cement content and type of coarse aggregate affect development of early aged stresses caused by shrinkage and thermally induced contraction. A probabilistic analysis of the factors that affect crack control using sawcut notches is presented in relation to different weather conditions (concrete placement temperature) at the time of construction, and concrete mixture characteristics such as fly ash replacement (FA) and cement factor (CF). Both of these significantly affect sawcut timing and depth requirement. The determination of crack initiation is based on fracture mechanics. Estimation of the time of cracking is based on predicted tensile strength and stress in the concrete at the bottom of the sawcut notch to assess the feasibility of crack control in the early stages of construction.
96

Structural Performance Evaluation of Interlocking Concrete Pavement Crosswalk Designs

Adhikari,Sudip 05 December 2008 (has links)
Interlocking Concrete Pavements (ICP) have been successfully used in many pavement applications all across the world. ICP design and analysis methods, construction practices and materials specifications have been developed. However, there is very limited field data to quantify structural performance with respect to traffic and environmental loadings. The interaction between traffic loadings and environmental factors needs to be explored in order to improve relationships between pavement performance and response. Pavement performance prediction in terms of fatigue cracking and surface rutting are essential for any mechanistically-based pavement design method. The estimation of the expected fatigue performance in the field is based on the quantification of the maximum tensile strain in bound base layers and the expected rutting performance is based on maximum vertical stress/strain in granular layers. This thesis presents an innovative research project involving the design, construction, instrumentation, performance modeling and distress evaluation of seven ICP crosswalks with four different design assemblies. The research projects were constructed at the Centre for Pavement and Transportation Technology (CPATT) test track and at the University of Waterloo ring road. Each of the test sections is instrumented with structural and environmental sensors of sensors to monitor the pavement performance under heavy truck traffic, typical municipal loadings and to quantify environmental effects. A database is generated and the measured stress, strain, temperature and moisture measurements are analysed to evaluate the expected long-term performance of the structural components of ICP crosswalk designs.
97

Structural Performance Evaluation of Interlocking Concrete Pavement Crosswalk Designs

Adhikari,Sudip 05 December 2008 (has links)
Interlocking Concrete Pavements (ICP) have been successfully used in many pavement applications all across the world. ICP design and analysis methods, construction practices and materials specifications have been developed. However, there is very limited field data to quantify structural performance with respect to traffic and environmental loadings. The interaction between traffic loadings and environmental factors needs to be explored in order to improve relationships between pavement performance and response. Pavement performance prediction in terms of fatigue cracking and surface rutting are essential for any mechanistically-based pavement design method. The estimation of the expected fatigue performance in the field is based on the quantification of the maximum tensile strain in bound base layers and the expected rutting performance is based on maximum vertical stress/strain in granular layers. This thesis presents an innovative research project involving the design, construction, instrumentation, performance modeling and distress evaluation of seven ICP crosswalks with four different design assemblies. The research projects were constructed at the Centre for Pavement and Transportation Technology (CPATT) test track and at the University of Waterloo ring road. Each of the test sections is instrumented with structural and environmental sensors of sensors to monitor the pavement performance under heavy truck traffic, typical municipal loadings and to quantify environmental effects. A database is generated and the measured stress, strain, temperature and moisture measurements are analysed to evaluate the expected long-term performance of the structural components of ICP crosswalk designs.
98

Development of a Prediction Model for Skid Resistance of Asphalt Pavements

Rezaei, Arash 2010 December 1900 (has links)
The skid resistance of asphalt pavement is a major characteristic that determines the driving safety on a road, especially under wet surface conditions. Skid resistance is primarily a function of the microtexture and macrotexture of a pavement surface. Microtexture is influenced by aggregate surface characteristics and is required to disrupt the continuity of surface water film and attain frictional resistance between the tire and the pavement surface. Macrotexture is affected mostly by mixture design or aggregate gradation and contributes to skid resistance by providing drainage paths of water that can be otherwise trapped between a tire and a pavement surface. The increase in macrotexture contributes to preventing hydroplaning and improving wet frictional resistance, particularly at high speeds. While much research has been conducted in the past to identify material factors that affect skid resistance, there is still a need to develop a model for predicting asphalt pavement skid resistance as a function of mixture characteristics and traffic level. The purpose of this study was to develop such a model based on extensive laboratory experiments and field measurements involving different mixture types and aggregate sources. The model incorporates functions that describe the resistance of aggregates to polishing and aggregate size distribution. The aggregate resistance to polishing was quantified by measuring aggregate texture using the Aggregate Imaging System (AIMS) before and after polishing in the Micro-Deval device. The analysis in this dissertation demonstrates how this model can be used to design mixtures and classify aggregates that provide desirable skid resistance levels.
99

Characterization of aggregate shape properties using a computer automated system

Al Rousan, Taleb Mustafa 17 February 2005 (has links)
Shape, texture, and angularity are among the properties of aggregates that have a significant effect on the performance of hot-mix asphalt, hydraulic cement concrete, and unbound base and subbase layers. Consequently, there is a need to develop methods that can quantify aggregate shape properties rapidly and accurately. In this study, an improved version of the Aggregate Imaging System (AIMS) was developed to measure the shape characteristics of both fine and coarse aggregates. Improvements were made in the design of the hardware and software components of AIMS to enhance its operational characteristics, reduce human errors, and enhance the automation of test procedure. AIMS was compared against other test methods that have been used for measuring aggregate shape characteristics. The comparison was conducted based on statistical analysis of the accuracy, repeatability, reproducibility, cost, and operational characteristics (e.g. ease of use and interpretation of the results) of these tests. Aggregates that represent a wide range of geographic locations, rock type, and shape characteristics were used in this evaluation. The comparative analysis among the different test methods was conducted using the Analytical Hierarchy Process (AHP). AHP is a process of developing a numerical score to rank test methods based on how each method meets certain criteria of desirable characteristics. The outcomes of the AHP analysis clearly demonstrated the advantages of AIMS over other test methods as a unified system for measuring the shape characteristics of both fine and coarse aggregates. A new aggregate classification methodology based on the distribution of their shape characteristics was developed in this study. This methodology offers several advantages over current methods used in practice. It is based on the distribution of shape characteristics rather than average indices of these characteristics. The coarse aggregate form is determined based on three-dimensional analysis of particles. The fundamental gradient and wavelet methods are used to quantify angularity and surface texture, respectively. The classification methodology can be used for the development of aggregate shape specifications.
100

Automated crack control analysis for concrete pavement construction

Jang, Se Hoon 01 November 2005 (has links)
The focus of this research is on the control of random cracking in concrete paving by using sawcut notch locations in the early stages of construction. This is a major concern in concrete pavement construction. This research also addresses a probabilistic approach to determine the optimum time and depth of sawcutting for newly constructed portland cement concrete pavements. Variability in climate conditions and material characteristics during the hardening process affects the potential of cracking at any sawcut depth. Several factors affecting the probability of crack initiation are material strength parameters, method and quality of curing, slab/subbase stiffness, the amount and depth of steel reinforcement, friction between the slab and the subbase, and concrete shrinkage. Other factors relevant to concrete mixture characteristics such as cement content and type of coarse aggregate affect development of early aged stresses caused by shrinkage and thermally induced contraction. A probabilistic analysis of the factors that affect crack control using sawcut notches is presented in relation to different weather conditions (concrete placement temperature) at the time of construction, and concrete mixture characteristics such as fly ash replacement (FA) and cement factor (CF). Both of these significantly affect sawcut timing and depth requirement. The determination of crack initiation is based on fracture mechanics. Estimation of the time of cracking is based on predicted tensile strength and stress in the concrete at the bottom of the sawcut notch to assess the feasibility of crack control in the early stages of construction.

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