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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.
171

Modeling of an Underground Mine Backfill Barricade

Ghazi, Sina 24 August 2011 (has links)
In this thesis finite element analyses were performed to investigate the behavior of fill fences installed in underground mines to retain Cemented Paste Backfill (CPB) pressure. For this purpose, two fill fences installed and tested in the Cayeli mine in Turkey were modeled using a 2-D nonlinear finite element analysis program, Augustus-2, and a 3-D nonlinear finite element analysis program VecTor4, and the results were compared with measured field data. Different models were employed representing the material properties, boundary conditions, reinforcement ratio, and geometric properties, and it was found that boundary conditions (stiffness of surrounding rocks) has the highest influence on the pressure capacity of the fence among the other factors. The accuracy of the Augustus-2 program was investigated by modeling and comparing the analytical response with test results of 12 axially restrained beams tested by Su et al. (2009).
172

Work Zone Throughput Models for Southern Ontario

Ahmadi, Bijan 01 December 2011 (has links)
Highway lane closures cause reductions in the traffic throughput which lead to premature queuing. To minimize user delays, contractors are required to keep highway lanes open during the peak traffic hours and work at nights. However, these limitations can reduce the quality of the work and extend project duration. Finding a right balance between the times that the lanes can be closed and the times they should be kept open can increase the efficiency of the contractors’ work. Over 100 hours of throughput data were collected in two phases from 2007 to 2010 from Southern Ontario highways. Using regression analysis, a generic and a highway specific model were developed predicting the mean throughput in approximately 50% of cases within one hundred vehicles per hour per lane of the actual mean. Also the Simplified Work Zone User Delay Analysis model, developed in Phase 1, was refined to investigate the resulting queues.
173

Assessing Organizational Competency in Infrastructure Asset Management: The Case of Water and Wastewater in Ontario Municipalities

Esmaili, Daryush 22 November 2012 (has links)
As infrastructure networks grow more complex, regulatory requirements become greater, populations grow, budgets become more limited, and the expectations of customers increase, municipalities are progressively being required to provide more for less. This is presenting some particular challenges to the long-term sustainability of buried water and wastewater infrastructure in Ontario. In response, municipalities are increasingly seeking to improve their business processes and asset management capabilities as a path to optimize the lifecycle of their infrastructure assets and ensure public safety, community development, and financial sustainability. This thesis presents an organizational performance measurement framework for municipal infrastructure asset management which was validated through interviews and surveys with international discipline experts. The resultant framework provides a high-level outline and suggestions for implementation of key objectives, 11 core critical success factors, and 135 quantitative performance indicators for municipal water and wastewater asset management organizations.
174

Beyond the Work Trip: Teen Travel in the Greater Toronto Area (GTA) and Policy Implications

Marzoughi, Reihane 16 March 2011 (has links)
Conventional transportation demand management approaches have had limited success in reducing automobile dependency. As a result, it has become increasingly important to understand the decision-making processes involved in determining travel behaviour. The purpose of this dissertation is to extend research on urban form and travel behaviour beyond adult travel by examining teen travelers aged 13-19 in the Greater Toronto Area. Data from the Transportation Tomorrow Survey (TTS) survey are used to study four main research questions: 1) How has teen mode choice changed from 1986 to 2006? 2) How do these choices vary as teens transition from the 13-15 age group to being of driving age (16-19)? 3) How do these choices vary across the different urban and suburban regions of the GTA? 4) What are some of the differences between teen travel and adult travel? The issue is further probed through the collection of quantitative and qualitative travel data from first year students at the University of Toronto, and a series of focus groups held in locations in the GTA. The first year survey explores attitudes towards different modes in relation to the locational attributes of the respondent‘s hometown neighbourhood. The focus group sessions involve interviews with 26 teen and a take-home parental questionnaire. Results show that across the GTA, active transportation has decreased while auto passenger mode shares have increased. Younger teens walk more and older teens take transit more for both school and discretionary travel. Jurisdictions with better transit supply and orientation have higher transit mode shares for school trips, but discretionary trips have low transit mode shares. Walk mode shares for both school and discretionary travel are similar across all jurisdictions, regardless of whether they are urban or suburban. Additionally, the survey participants' narratives illustrate that the desire to travel actively and independently is strong. However, the reality of the final travel choice is determined by the presence of supportive infrastructure that facilitates active mode choices while shaping perceptions and attitudes formed as a result of daily travel experiences. Findings illustrate the relevance of qualitative work in advancing transportation research--particularly in understanding human travel decisions.
175

Sulfate Resistance and Properties of Portland-limestone Cements

Ramezanianpour, Amir Mohammad 04 September 2012 (has links)
Portland-limestone cements (PLC) have been used in practice for a considerable period of time in several countries. In 2008, the CSA A3000 cements committee approved the addition of a new class of cement with up to 15% interground limestone. The CSA A23.1 concrete committee also approved the use of PLC in concrete in 2009. However, to date, due to uncertainty about the performance of Portland-limestone cements in sulfate environments, their use has not been allowed in sulfate exposures. In this study, the sulfate resistance of five different Portland-limestone cements and their combinations with various amounts of supplementary cementitious materials (SCMs) were examined. Besides the standard tests performed at 23 °C, a modified version of the ASTM C1012 test was developed in this study (adopted in 2010 as CSA A3004-B) and used to investigate the possibility of thaumasite form of sulfate attack at 5 °C. It was found for tests conducted at 23 °C that while 100% cement mixes deteriorated in sulfate exposure due to conventional sulfate attack, partially replacing the Portland cements and Portland-limestone cements with 30% or 50% slag was effective in making the mixes highly sulfate-resistant. In sulfate exposure at 5 °C, all of the 100% cement mortar bars failed the test and had completely disintegrated due to the formation of thaumasite. Partially replacing cement with 30% slag was effective in controlling the deterioration at 5 °C only for Portland cements and not Portland-limestone cements. However, all the combinations of the cements with 50% slag were resistant to the thaumasite form of sulfate attack. In a parallel study, the hydration of Portland-limestone cements and the relationship between strength and porosity of mortar samples were examined. The results of hydration studies revealed that the limestone portion of Portland-limestone cements reacts with the alumina phases and produces carboaluminates, which contributes to the strength. As the limestone content of the cement increased, the shift in the optimum level of SCM providing maximum strength and minimum porosity was attributed to the availability of more alumina, which allowed more limestone to participate in the hydration reactions, forming additional carboaluminate hydrates.
176

Seismic Performance of Steel Moment-resisting Frames with Nonlinear Replaceable Links

Shen, Yunlu 14 July 2009 (has links)
This thesis presents the development and the seismic performance evaluation of steel MRFs with nonlinear replaceable links. Although existing MRFs can provide life safety during a design level earthquake, they are expected to sustain significant damage at the locations of flexural yielding fuses in the beams. The design of the fuse is also interlinked with the design of the beam, often resulting in over-design. These drawbacks can be mitigated by introducing replaceable links at the locations of expected inelastic action. Four full-scale beam-to-column subassemblages with two link types were tested under cyclic loading: i) double channels with bolted web connections, ii) W-sections with bolted end plate connections. The experiments demonstrated that MRFs with replaceable links can provide strength and ductility equivalent to existing MRFs. Finite element models were then developed to capture the observed experimental responses, including local buckling, bolt slipping, and bolt bearing. Finally, preliminary design guidelines were proposed.
177

Comparisons between MATSim and EMME/2 on the Greater Toronto and Hamilton Area Network

Gao, Wenli 07 August 2009 (has links)
The agent-based micro-simulation modelling technique for transportation planning is rapidly developing and is being applied to practice in recent years. In contrast to conventional four-step modelling with static assignment theory, this emerging technique employs a dynamic assignment principle. Based on summary of various types of traffic assignment models and algorithms, the thesis elucidates in detail the theories of two models, MATSim and EMME/2, which represent two genres of traffic assignment, i.e., dynamic stochastic stationary state assignment and static deterministic user equilibrium assignment. In the study, the two models are compared and validated to reflect both spatial and temporal variation of the traffic flow pattern. The comparison results indicate that numerical outputs produced by MATSim are not only compatible to those by EMME/2 but more realistic from a temporal point of view. Therefore, agent-based micro-simulation models reflect a promising direction of next generation of transportation planning models.
178

Dynamic Testing of Soft and Ultra-soft Materials

Huang, Sheng 20 January 2010 (has links)
A modified Split Hopkinson Pressure Bar (SHPB) system is used to determine the mechanical properties of soft and ultra-soft materials. An aluminum bar is introduced to reduce the impedance mismatch between the test system and sample. The small signal of the forces was measured by a quartz crystal gauge system. The high precision Laser gap gauge (LGG) system was used to measure the deformation of samples. The compressive tests of Cemented Paste Backfill (CPB), fresh CPB and Polymethylmethacrylate (PMMA) and the fracture toughness tests of PMMA were conducted to approve the legitimacy of our modified SHPB system. From these experiments, the efficiency and economy of the modified SHPB system were attested.
179

Beyond the Work Trip: Teen Travel in the Greater Toronto Area (GTA) and Policy Implications

Marzoughi, Reihane 16 March 2011 (has links)
Conventional transportation demand management approaches have had limited success in reducing automobile dependency. As a result, it has become increasingly important to understand the decision-making processes involved in determining travel behaviour. The purpose of this dissertation is to extend research on urban form and travel behaviour beyond adult travel by examining teen travelers aged 13-19 in the Greater Toronto Area. Data from the Transportation Tomorrow Survey (TTS) survey are used to study four main research questions: 1) How has teen mode choice changed from 1986 to 2006? 2) How do these choices vary as teens transition from the 13-15 age group to being of driving age (16-19)? 3) How do these choices vary across the different urban and suburban regions of the GTA? 4) What are some of the differences between teen travel and adult travel? The issue is further probed through the collection of quantitative and qualitative travel data from first year students at the University of Toronto, and a series of focus groups held in locations in the GTA. The first year survey explores attitudes towards different modes in relation to the locational attributes of the respondent‘s hometown neighbourhood. The focus group sessions involve interviews with 26 teen and a take-home parental questionnaire. Results show that across the GTA, active transportation has decreased while auto passenger mode shares have increased. Younger teens walk more and older teens take transit more for both school and discretionary travel. Jurisdictions with better transit supply and orientation have higher transit mode shares for school trips, but discretionary trips have low transit mode shares. Walk mode shares for both school and discretionary travel are similar across all jurisdictions, regardless of whether they are urban or suburban. Additionally, the survey participants' narratives illustrate that the desire to travel actively and independently is strong. However, the reality of the final travel choice is determined by the presence of supportive infrastructure that facilitates active mode choices while shaping perceptions and attitudes formed as a result of daily travel experiences. Findings illustrate the relevance of qualitative work in advancing transportation research--particularly in understanding human travel decisions.
180

Freight Market Interactions Simulation (FREMIS): An Agent-based Modelling Framework

Cavalcante, Rinaldo 19 March 2013 (has links)
Freight transport is the output of an economic market, which converts commodity flows into vehicle flows. Interactions in this market influence vehicle flows and since freight market characteristics (product differentiation and economies of scale/scope) violate perfect competition conditions, the output of this market cannot be predicted directly, unless these interactions are represented in the forecasting models. Traditional freight modelling frameworks do not consider these interactions and consequently they may provide inaccurate freight flow forecasts. In this dissertation, a freight modelling framework is proposed using simulation of freight agent interactions in the economic market to forecast freight flows. The framework is named FREMIS (FREight Market Interactions Simulation). The FREMIS framework consists of two demand models to represent shipper decisions (bundling of shipments and carrier selection) in the market and functions based on profit maximizing behaviour to simulate carrier proposals for contracts. Besides that, learning models are proposed to simulate agent learning processes based on their interactions. The framework was developed aiming to create a realistic representation of freight markets using feasible data collection methods. To illustrate the feasibility of the data collection, a customized web survey was implemented with shippers and carriers in a freight market. Two probabilistic models were developed using the data. The first model, a shipment bundling model was proposed combining a probabilistic model and a vehicle routing algorithm. The results of the probabilistic model are presented in this dissertation, where the locations of shipments (origin and destination) influence the probability of bundling them. Second, three carrier selection models were developed aiming to analyse the nonresponse bias and non-attendance problem in the survey. All of these models assumed heteroskedasticity (different scale or variance) in shipper behaviour. In all models, the hypothesis of agents’ heteroskedasticity cannot be rejected. Besides that, nonresponse bias and non-attendance problem were identified in the survey. In conclusion, the models obtained from the survey were consistent with their behavioural assumptions and therefore they can be adopted during FREMIS implementation.

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