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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.

Resilient Modulus and Dynamic Poisson's Ratio of Asphaltic Concrete Mixes

Lee, Michael A. 12 1900 (has links)
<p>Increased interest in rational approaches to flexible pavement design, rather than the usual empirical methods, has brought about an urgent need for a better understanding of the material properties involved. In this study, laboratory equipment capable of providing reliable measurements of the material properties for asphaltic concrete mixes, under variable stress and temperature conditions has been developed. The basic material properties obtained from these measurements are the resilient modulus (MR) and dynamic Poisson's ratio (v), which are the required inputs for the elastic analysis of flexible pavement structures.</p> <p>Tests have indicated that temperature is the main parameter affecting the resilient modulus of asphaltic concrete mixes, with deviator stress and confining pressure secondary in effect. Based on tests performed on a few samples, the dynamic Poisson's ratio was found to increase with temperature from about 0.24 at 10ºC (50ºF) to approximately 0.46 at 42ºC (108ºF). Confining pressure was found to have little or no effect on the dynamic v.</p> <p>Analysis using a linear elastic flexible pavement computer programme has indicated a significant reduction in...a mix with a higher MR value. This demonstrates the advantage of utilizing the structural analysis approach to flexible pavement design for more efficient use of materials.</p> / Master of Engineering (ME)


Hamelin, Jamie 08 1900 (has links)
<p>In recent years, the use of tuned liquid dampers (TLD) as dynamic vibration absorbers has increased in popularity due to their low cost and ease of installation. A TLD is a partially fluid filled tank (commonly water) that has a fundamental sloshing frequency close to the natural frequency of the structure in the vibration mode to be suppressed. Typically, water alone is insufficient to achieve the required level of optimal damping. One approach that is used to increase the damping of the TLD is to install flow damping devices (screens) into the tank. In this study horizontal slat screens are selected for investigation. For a given target response acceleration an optimal level of damping can be achieved. However, as the structural response deviates from this target value the efficiency of the structure-TLD system is significantly reduced. To increase the efficiency, an investigation into the applicability of slat screens with a varying loss coefficient is undertaken in this study.</p> <p>A TLD equipped with slat screens bf different slat heights, edge geometries, and solidities is experimentally investigated. The TLD is subjected to shake-table tests under sinusoidal excitation for a range of amplitudes that correspond to a practical range of peak hourly horizontal structural accelerations. The variation in screen losses (C<sub>L</sub>) is correlated with the Keulegan-Carpenter (<em>KC</em>) number.</p> <p>An equivalent mechanical model is utilized by analyzing the TLD as an equivalent tuned mass damper (TMD). In addition, a nonlinear numerical model based on shallow water theory is investigated. The influence of slat height on the free surface response, base shear forces, and energy dissipation is assessed.</p> <p>A TLD equipped with various screen geometries is mathematically modelled in a hypothetical structure-TLD system. This system demonstrates the ability of slat screens with a varying loss coefficient to maintain a near optimum level of damping over a wide range of structural accelerations.</p> / Master of Applied Science (MASc)


Lewis, Julia M. 09 1900 (has links)
<p>Tuned-liquid dampers (TLDs) can be used as vibration absorbers for tall buildings. The ability of TLDs to decrease a building's motions is highly dependent on them being tuned to the building's natural frequency. In the present study natural frequency and damping estimates are determined for a 187 m tall building equipped with TLDs. A properly tuned structure-TLD system acts as a coupled two-degree-of-freedom (2DOF) system. In this study several MATLAB (2009) programs were developed in order to determine the dynamic properties of both single-degree-of-freedom (SDOF) and 2DOF systems. These programs Were based on the statistical maximum likelihood (ML) and least squares (LS) methods. The ML programs are based on earlier work by Montpellier (1997) and the LS programs were developed independently. All of the programs were verified using spectral and time-history data with known dynamic properties. The results of the programs were also compared to results generated by the well-known half-power bandwidth and random decrement methods: The ML and LS programs were found to produce results that were superior to the half-power bandwidth method and comparable to the random decrement program for SDOF systems. The ML and LS programs are superior to the half-power bandwidth and random decrement programs for analyzing coupled 2DOF systems as they are able to determine distinct property estimates for each mass. The natural frequency of the building studied for this project was found to be significantly higher than predicted at the time of its design. Thus the TLDs were not optimally tuned to the building's actual natural frequency and as a result the studied building was behaving as a SDOF system. Therefore the dynamic properties estimated in this study are those of a SDOF system. However, the methods developed herein could be applied to a 2DOF system in the future.</p> / Master of Applied Science (MASc)


Ahmed, Sadik 09 1900 (has links)
<p>p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.5px Times}</p> <p>The objective of this thesis is to investigate the potential of ensemble</p> <p>meteorological forecasts (15 members for each day) in improving ensemble flow</p> <p>prediction up to 14 days ahead. Large scale ensemble meteorological forecasts generated</p> <p>by the National Centers for Environmental Prediction's (NCEP) Global Forecast System</p> <p>(GFS) are used. The hydrologic model used in watershed analysis of the study area is</p> <p>Hydrologiska Byrâns Vattenbalan-avdelning (HBV). The study area is located in the</p> <p>Saguenay-Lac-Saint Jean watershed in northeastern Canada and comprises the Serpent</p> <p>River and Chute-du-Diable basins and a reservoir in Chute-du-Diable.</p> <p>The NCEP ensemble meteorological forecast data is initially used as input in the p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.5px Times} span.s1 {font: 7.5px Helvetica}</p> <p>hydrological model HBV to simulate ensemble reservoir inflows and the Serpent River</p> <p>flows for 5 to 14 days ahead. The ensemble inflow and flow forecasts are compared with</p> <p>the case where only observed historical data are used. The study results show that there is</p> <p>a significant improvement in the model forecast performance when NCEP forecast data</p> <p>are used. The improvement for 5 to 14 day forecasts is revealed by an approximately 20%</p> <p>decrease in root mean square error (RMSE) for both reservoir inflow and river flow. A</p> <p>decrease in the Brier score (BS) and rank probability score (RPS) indicates considerable</p> <p>improvement and an increase in the correlation coefficient (r) and the Nash and Sutcliffe</p> <p>coefficient (R²) is shown for reservoir inflow and the Serpent River flow respectively,</p> <p>indicating the advantage of using NCEP data. This improvement is also revealed by the p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.5px Times}</p> <p>visual inspection of scatter plots, hydrographs of ensemble mean and ensemble members.</p> <p>The hydrologic forecasts are also assessed on a seasonal basis indicating an improvement</p> <p>in forecasting indicated by a 30% decrease in RMSE during the spring season, and a</p> <p>decrease in BS and RPS values. For other seasons, specifically autumn and summer, the</p> <p>use of the ensemble meteorological forecasts do not provide significant improvement</p> <p>because of the poor skill of predicted precipitation. More accurate predictions of reservoir</p> <p>inflow and river flow with adequate lead time will assist in improving relevant issues in</p> <p>water resources management and planning.</p> / Master of Applied Science (MASc)


Khosravi, Fard Ehsan 10 1900 (has links)
<p>The behavior of subgrade soils with different water contents under freeze-thaw conditions is a significant factor to be considered in pavement engineering, since freeze-thaw cycles substantially affect deformation of subgrade under cyclic loading, which in turn influence the performance of pavements.<br /> In this study, the resilient modulus tests were performed on unfrozen silty clay before and after the first freeze-thaw cycle. Resilient modulus tests were carried out at various water contents including 5%, 8%, 10%, 12% and 15%. The behavior and response of the samples were monitored and recorded, and are compared through this report. In addition to resilient modulus tests, the accumulative deformation of the samples under cyclic loading was investigated. The results reveal that freeze-thaw cycles have the potential to have significant impact on permanent deformation of silty-clay under cyclic load.</p> / Master of Engineering (ME)

Behaviour of Partially Grouted Nominally Reinforced Masonry Shear Walls under Dynamic Loading

Kasparik, Tomas January 2009 (has links)
<p>The current Canadian masonry standard CSA S304.1 (2004) deals with the design of unreinforced and reinforced concrete masonry shear walls. The use of one or the other type of wall construction is limited to a particular seismic activity zone based on the seismic hazard index. The code does not provide any provisions for partially grouted shear walls in regions with moderate seismic demand. The experimental program described in the thesis focuses on the dynamic performance of partially grouted nominally reinforced concrete masonry shear walls having less steel and larger spacing than specified by the Canadian masonry standard for the minimum seismic requirements.</p> <p>A total of six reduced scale shear walls were designed and constructed to fail in flexure. A constant axial load was present throughout the test, which represented a single story building. The walls were grouped into three categories, Type I, II and III. Type I and III walls had reinforcement present only at the ends of the wall with vertical reinforcement ratios of 0.12% and 0.20%, respectively. Type II walls had an additional reinforcement located mid-length of the wall with a reinforcement ratio of 0.17%. Two identical walls were tested for each type with the exception of the Type III, where only one wall was tested. The walls were subject to dynamic loading of a scaled 1940 EI-Centro earthquake N-S component. The experimental results were evaluated and discussed pertaining to behaviour, lateral load capacity, stiffness, period, displacement ductility and load reduction factors.</p> <p>The general behaviour of the tested shear walls was dominated by rocking motion where a full length mortar joint crack developed, along with the yielding of reinforcement. The rocking motion was able to dissipate energy instead of the more common diagonal cracking and crushing of masonry. Type I and II walls had yields close the predicted values, while Type III wall had a lower yield point than predicted. All walls had similar trends of stiffuess degradation. The period increased by a factor of 2 or more during the course of testing. An idealized bilinear envelope was used to calculate the displacement ductility. It was found to be greater than 2 with load reduction factors ranging from 1.9 to 2.6.</p> <p>It was concluded that nominally reinforced partially grouted walls are potentially viable to be used in seismic zones where the seismic hazard index exceeds 0.35.</p> / Master of Applied Science (MASc)

Behaviour of Reduced-Scale Reinforced Concrete Masonry Shear Walls and Components

Hughes, Kevin J. January 2010 (has links)
<p>Reduced-scale models have become an attractive alternative to full-scale experimental laboratory testing due to both physical and fmandal restrictions. In order to have confidence in the ability of a reduced-scale model to replicate fullscale prototype behaviour, test data from reduced-scale research must be correlated and compared to test results of full-scale, prototype, materials. The overall goal of the following thesis is to provide a detailed comparison between third-scale models and full-scale prototype masonry materials, assemblages and wall components. The study includes a total of three phases of experimental testing. The first phase focuses on the individual elements that make up a reinforced concrete masonry shear wall. Elements examined include: third-scale model concrete blocks, mortar, grout and reinforcing steel. The second phase of the reseflrch project focuses on testing different configurations of masonry assemblages in an attempt to combine individual third-scale model elements into a composite assemblage to correlate behaviour to that ofpreviously tested full-scale<br />assemblages. The third and final phase of research compares two third-scale reinforced masonry shear walls to full-scale walls testing previously at McMaster University. In general, the third-scale model specimens showed good relation to full-scale prototypes for both the individual components and shear walls.</p> / Master of Applied Science (MASc)

Effects of Waste Glass and Polymer Addition on the Performance of Concrete Masonry Blocks

Mihaljevic, Nicole Sylvia 10 1900 (has links)
<p>Concrete masonry blocks are widely used in North America and the world; however, production poses some environmental implications, specifically the depletion of natural resources and contribution to the release of carbon dioxide into the atmosphere. Accordingly, methods to improve the sustainability of the industry need to be developed. The replacement of cement with post -consumer waste glass powder and/or the replacement of fine aggregate with post-consumer waste polymer in the production of concrete blocks are proposed as potential options to reduce the environmental impact of block production while maintaining adequate block performance.<br /> The effect of using glass powder and polymers on the block and prism properties has been analyzed to determine the most effective implementation of these post-consumer waste materials. Physical properties, mechanical properties and alkali-silica reaction of the blocks and the mechanical properties of the prisms were tested. From the experimental program, it was determined that replacing Portland cement with waste glass powder up to 25% had no detrimental effect on the block and prism properties. Replacing the sand with polymer aggregate was found to have a detrimental impact on the strength of the block. The effect of adding up to 6% polymer aggregate as sand replacement on the prism mechanical properties was found to be minimal. The reduction in block compressive strength when polymer aggregates are used is attributed to the increase in the material's porosity.</p> / Master of Applied Science (MASc)

Strengthening of Reinforced Concrete Beams using Anchored Near Surface Mounted Bars

Petrina, Antony David 06 1900 (has links)
<p>To delay the onset of delamination and to ensure the CFRP continues to supply strength after initial delamination of reinforced concrete beams strengthened with near surface mounted CFRP bars, a new mechanical anchoring system was developed and tested in this investigation. The anchors were integrally connected to the CFRP bars and extracted from a proprietary product commonly known as NEFMAC. The anchored bars were installed by cutting grooves into the concrete cover, boring holes at anchor locations and using epoxy to bond the strengthening bars to the groove surfaces.<br /> <br /> A total of seven simply-supported reinforced concrete beams were tested in fourpoint bending to study the effectiveness of the proposed anchoring system. One beam served as a control specimen, two beams were strengthened with unanchored near surface mounted bars and the remaining four beams were strengthened with the anchored bars. As an exploratory study two of the four anchored beams were also strengthened with anchored near surface mounted CFRP transverse bars to determine if the system is an acceptable substitute for internal steel stirrups.<br /> <br /> Results of this study reveal that the anchors can delay delamination and after initial delamination, the anchored beams continued to carry the applied load whereas the unanchored beams lost strength immediately following concrete cover delamination. Although there was not a significant gain in flexural capacity in the anchored beams relative to the unanchored beams, the improved ductility provided by the new system shows promise. Further investigation is needed to determine the number of anchors needed, depth of penetration, size and location of such anchors to achieve composite behaviour between the strengthening bars and the reinforced concrete section.</p> / Master of Applied Science (MASc)

Comparison of Downscaled RCM and GCM data for Hydrologic Impact Assessment

Sharma, Manu 06 1900 (has links)
<p>From observations of increases in global average air and oceanic temperatures, melting of polar ice and significant increases in net anthropogenic radiative forcing, it is clear our global climate system is undergoing substantial warming (IPCC, 2007). A key area of concern for hydrologists and engineers alike is to determine how this warming will affect various hydrologic processes. To date, climate change impact studies have generally involved the downscaling of large-scale atmospheric predictors with the result then being input into a hydrological model to see how flow in a river/basin will change under various future climate change scenarios. Although many studies have been completed using large scale global climate model (GCM) data, few studies have shown the strength of regional climate models (RCM). In this work, a comparison between the effectiveness of using CRCM4.2 vs. CGCM3.1 data in a climate change impact study (climate forcing under the SRES A2 climate scenario) is considered. The study area is the Chute-du-Diable sub-basin located within the Saguenay-Lac-Saint-Jean Watershed in Quebec, Canada. Downscaled results are compared with observed meteorological data for the years 1961-1990 at the Chute-des-Passes (CDP) and Chute-du-Diable (CD D) weather stations; and flow is simulated in the Mistassibi River and the Chute-du-Diable reservoir. A regression technique (SDSM) and a dynamic artificial neural network model (Time lagged feed-forward neural network (TLFN)) are used for downscaling the CRCM4.2 and CGCM3.1 data, and the HBV2005 hydrological modeling system is used for simulating flows in the watershed. For the current period (1961-1990), downscaling results reveal that downscaled CRCM4.2 is closer to observed meteorological data at both CDD and CDP stations than downscaled CGCM3.1 is. The Wilcoxon Rank-Sum test and Levene test reveal that regardless of the climate model, both TLFN and SDSM are capable of capturing the monthly means and variance of precipitation and temperature. Statistical results reveal that TLFN is best for downscaling temperature and SDSM is best for downscaling precipitation. With respect to the future climate scenario, regardless of the climate model or the downscaling method, a 1 to 3 ° C increase in annual mean maximum temperature and a 1 to 4°C increase in annual mean minimum temperature are predicted for the 2050s future period. In the case for precipitation, the CRCM4.2 model shows increases in annual precipitation will vary from 1 to 7% in the 2050s regardless of the downscaling method used. The CGCM3.1 model on the other hand, shows increases in annual precipitation ranging from 15 to 23% regardless of the downscaling method employed. Additionally, simulations of river flows and reservoir inflows reveals significant changes in mean flow will occur as a result of the warming trend. Simulations show that for both SDSM and TLFN, CRCM4.2 and CGCM3.1 show an increase in river flow and reservoir flows throughout all seasons except for the summer where reduction of flow is observed. Annually, at the Chute-du-Diable reservoir mean flow changes vary from a 16-28% increase in the 2050s and at the Mistassibi River annual mean flow changes vary from a 12-62% increase. In all cases CGCM3.1 model shows a larger increasing trend than the CRCM4.2 model.</p> / Master of Applied Science (MASc)

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