Master of Science / Department of Civil Engineering / Robert Peterman / A flowable hybrid concrete mix with a spread of 17 to 20 inches was created with a superplasticizer to be used in post-tension haunch-slab (PTHS) bridges where rebar congestion is heaviest. The mix would allow for proper concrete consolidation. A conventional concrete mix with a slump of three to four inches was also created to be placed on top of the hybrid mix. The conventional mix would be used to create a sloping surface on the top of the concrete. The two mixes could be combined in the PTHS bridge deck and act as one monolithic specimen. Standard concrete tests such as compressive strength, tensile strength, modulus of elasticity, permeability, freeze/thaw resistance, and coefficient of thermal expansion were determined for the mixes and compared. Core blocks were cast using both mixes and composite cores were drilled. The cores were tested and their composite split-tensile strengths were compared to the split-tensile strengths of cylinders made from the respective mixes. A third concrete mix was made by increasing the superplasticizer dosage in the hybrid concrete mix to create a self-consolidating concrete (SCC) mix with a 24-inch spread. The SCC mix was created as a worst-case scenario and used in the determination of shear friction. Eighty-four push-off shear friction specimens were cast using the SCC mix. Joint conditions for the specimens included uncracked, pre-cracked, and cold-joints. Uncracked and pre-cracked specimens used both epoxy- and non-epoxy-coated shear stirrups. Cold-joint specimens used both the SCC mix and the conventional concrete mix. Joint-conditions of the cold-joint specimens included a one-hour cast time, a seven-day joint with a clean shear interface, and a seven-day joint with an oiled shear interface. The shear friction specimens were tested using a pure shear method and their results were compared to the current American Concrete Institute code equation.

Master of Science / Department of Civil Engineering / Sunanda Dissanayake / In order to improve safety of the overall surface transportation system, each of the critical areas needs to be addressed separately with more focused attention. Statistics clearly show that large-truck crashes contribute significantly to an increased percentage of high-severity crashes. It is therefore important for the highway safety community to identify characteristics and contributory causes related to large-truck crashes. During the first phase of this study, fatal crash data from the Fatality Analysis Reporting System (FARS) database were studied to achieve that objective. In this second phase, truck-crashes of all severity levels were analyzed with the intention of understanding characteristics and contributory causes, and identifying factors contributing to increased severity of truck-crashes, which could not be achieved by analyzing fatal crashes alone. Various statistical methodologies such as cross-classification analysis and severity models were developed using Kansas crash data. Various driver-, road-, environment- and vehicle- related characteristics were identified and contributory causes were analyzed. From the cross-classification analysis, severity of truck-crashes was found to be related with variables such as road surface (type, character and condition), accident class, collision type, driver- and environment-related contributory causes, traffic-control type, truck-maneuver, crash location, speed limit, light and weather conditions, time of day, functional class, lane class, and Average Annual Daily Traffic (AADT). Other variables such as age of truck driver, day of the week, gender of truck-driver, pedestrian- and truck-related contributory causes were found to have no relationship with crash severity of large trucks. Furthermore, driver-related contributory causes were found to be more common than any other type of contributory cause for the occurrence of truck-crashes. Failing to give time and attention, being too fast for existing conditions, and failing to yield right of way were the most dominant truck-driver-related contributory causes, among many others. Through the severity modeling, factors such as truck-driver-related contributory cause, accident class, manner of collision, truck-driver under the influence of alcohol, truck maneuver, traffic control device, surface condition, truck-driver being too fast for existing conditions, truck-driver being trapped, damage to the truck, light conditions, etc. were found to be significantly related with increased severity of truck-crashes. Truck-driver being trapped had the highest odds of contributing to a more severe crash with a value of 82.81 followed by the collision resulting in damage to the truck, which had 3.05 times higher odds of increasing the severity of truck-crashes. Truck-driver under the influence of alcohol had 2.66 times higher odds of contributing to a more severe crash. Besides traditional practices like providing adequate traffic signs, ensuring proper lane markings, provision of rumble strips and elevated medians, use of technology to develop and implement intelligent countermeasures were recommended. These include Automated Truck Rollover Warning System to mitigate truck-crashes involving rollovers, Lane Drift Warning Systems (LDWS) to prevent run-off-road collisions, Speed Limiters (SLs) to control the speed of the truck, connecting vehicle technologies like Vehicle-to-Vehicle (V2V) integration system to prevent head-on collisions etc., among many others. Proper development and implementation of these countermeasures in a cost effective manner will help mitigate the number and severity of truck-crashes, thereby improving the overall safety of the transportation system.

Doctor of Philosophy / Department of Civil Engineering / Kyle A. Riding / ASTM recently adopted the Standard Test Method for Evaluating Bond of Seven-Wire Steel Prestressing Strand as ASTM A1081, a pull-out test procedure developed for verifying the ability of steel strands to bond to cementitious materials prior to their use as tensile reinforcement in prestressed concrete sections. The required by ASTM International precision and bias statement has not been developed for this test method. In addition, a minimum threshold value that will ensure only adequately bonding strand sources will be accepted has not yet been applied to ASTM A1081. The test method was developed after findings that prestressing steel strand sources of identical type and grade vary significantly as far as their bonding capacity. Bond is a crucial aspect of the prestressing force being transferred into the concrete, and insufficient bonding action can result in the prestressed concrete section lacking in capacity to sustain the loads that it was designed for. After an initial survey of the pull-out strength of North American Strand in mortar, three strands of differing pull-out strengths were selected for inclusion in further testing. A precision and bias statement for ASTM A1081 was developed by first performing ruggedness testing to determine how the results are affected by allowable variations in methods and materials, and followed by an inter-laboratory study to determine the reproducibility of the test method. Once the precision and bias statement for the standard test method was developed, the same strand sources were tested for their performance in concrete beams. Statistical analysis of the flexural beam testing data and correlation with the prestressing strand sources’ ASTM A1081 test results was performed, and the industry was provided with minimum acceptance criteria for prestressing strand tested by ASTM A1081, along with recommendations regarding the standard test method and aspects of prestressed concrete design.

Current analysis procedures for new reinforced concrete structures are typically based on linear-elastic principles. However, under certain conditions, it may be necessary to analyze a structure to more accurately predict its structural behaviour. Such an analysis can be performed using nonlinear analysis procedures which typically require specialized software. This type of software is limited in number and most available programs do not adequately capture shear-related influences, potentially severely overestimating strength and ductility in shear-critical structures. The purpose of this study is to develop and verify an analytical procedure for the nonlinear analysis of frame structures with the aim of capturing shear-related mechanisms as well as flexural and axial effects. A previously developed analysis program, VecTor5, is further developed for this purpose. Originally formulated in the early 1980s at the University of Toronto, VecTor5 is based on the Modified Compression Field Theory (MCFT) and is capable of performing nonlinear frame analyses under temperature and monotonic loading conditions. Although providing generally satisfactory simulations, there are a number of deficiencies present in its computational algorithms. This study consists of three major parts: improvement of the original analysis procedure for monotonic loading conditions, expansion of the procedure for general loading conditions including the special cases of cyclic and reversed-cyclic loading, and further development of the procedure for dynamic loading conditions including time-varying base accelerations, impulse, impact and blast forces, initial mass velocities, and constant mass accelerations. Each part is supported by verification studies performed on a large number and variety of previously tested structures available in the literature. In addition, considerations in nonlinear modelling are discussed with the aim of providing guidelines for general modelling applications. Analyses of 63 previously tested structures, half of which are shear-critical, demonstrate that the developed analytical procedure is highly successful in simulating the experimental responses in terms of load-deflection response, reinforcement strains, crack widths, failure mode, failure displacement, total energy dissipation, displacement ductility ratio, and post-peak vibrational characteristics.

The population and economic growth experienced by Canadian metropolitan areas in the past twenty years, has been associated with increased levels of car ownership and vehicle kilometres travelled leading to a deterioration of air quality and public health and an increase in greenhouse gas emissions. The need to modify urban growth patterns has motivated planning agencies in Canada to develop a broad range of policies aiming at achieving a more sustainable transportation sector. The challenge however, remains in the ability to test the effectiveness of proposed policy measures. This situation has led to a renewed interest in integrated land-use and transport models to support transport policy appraisal. This research is motivated by the need to improve transport policy appraisal through the use of integrated land-use and transport models linked with a range of sub-models that can reflect transport externalities. This research starts with an exploration of the transport policy environment in Canada through a questionnaire-based survey conducted with planners and policy-makers. The survey results highlight the need for tools reflecting the sustainability impacts of proposed policies. While the second part of this research explores sustainability indicators and recommends a set of social, economic, and environmental measures, linked with integrated land-use and transport models; effort is dedicated to estimate the environmental indicators as part of this thesis. As such, the third part of this research involves the development of an emission-dispersion-exposure modelling framework. The framework includes a suite of sub-models including an activity-based travel demand model (TASHA), an emission factor model (Mobile6.2C), a meteorological model (CALMET), and a dispersion model (CALPUFF). The framework is used to estimate link-based emissions of light-duty vehicles in the Greater Toronto Area under a base scenario for 2001. Dispersion of emissions is then conducted and linked with population in order to estimate exposure to air pollution.

The goal of this research is to develop a robust, continuum-based approach for a three-dimensional, Finite Element Method (FEM) simulation of layered geomaterials. There are two main approaches to the numerical modeling of layered geomaterials; discrete or discontinuous techniques and an equivalent continuum concept. In the discontinuous methodology, joints are explicitly simulated. Naturally, discrete techniques provide a more accurate description of discontinuous materials. However, they are complex and necessitate care in modeling of the interface. Also, in many applications, the definition of the input model becomes impractical as the number of joints becomes large. In order to overcome the difficulties associated with discrete techniques, a continuum-based approach has become popular in some application areas. When using a continuum model, a discrete material is replaced by a homogenized continuous material, also known as an 'equivalent continuum'. This leads to a discretization that is independent of both the orientation and spacing of layer boundaries. However, if the layer thickness (i.e., internal length scale of the problem) is large, the classical continuum approach which neglects the effect of internal characteristic length can introduce large errors into the solution. In this research, a full 3D FEM formulation for the elasto-plastic modeling of layered geomaterials is proposed within the framework of Cosserat theory. The effect of the bending stiffness of the layers is incorporated in the matrix of elastic properties. Also, a multi-surface plasticity model, which allows for plastic deformation of both the interfaces between the layers and intact material, is introduced. The model is verified against analytical solutions, discrete numerical models, and experimental data. It is shown that the FEM Cosserat formulation can achieve the same level of accuracy as discontinuous models in predicting the displacements of a layered material with a periodic microstructure. Furthermore, the method is capable of reproducing the strength behaviour of materials with one or more sets of joints. Finally, due to the incorporation of layer thickness into the constitutive model, the FEM Cosserat formulation is capable of capturing complicated failure mechanisms such as the buckling of individual layers of material which occur in stratified media.

The characteristics of cement kiln dusts (CKDs) and their effects as partial replacement of Portland Cement (PC) were studied in this research program. The materials used in this study were two different types of PC (normal and moderate sulfate resistant) and seven CKDs. The CKDs used in this study were selected to provide a representation of those available in North America from the three major types of cement manufacturing processes: wet, long-dry, and preheater/precalciner. Two fillers (limestone powder and quartz powder) were also used to compare their effects to that of CKDs at an equivalent replacement of PC. It was found that CKDs can contain significant amounts of amorphous material (>30%) and clinker compounds (>20%) and small amounts of slag and/or flyash (<5%) and calcium langbeinite (<5%). The study found that CKDs from preheater/precalciner kilns have different effects on workability and heat evolution than CKDs from wet and long-dry kilns due to the presence of very reactive and high free lime contents (>20%). The blends with the two CKDs from preheater/precalciner plants had higher paste water demand, lower mortar flows, and higher heat generation during initial hydrolysis in comparison to all other CKD-PC blends and control cements. The hardened properties of CKD as a partial substitute of PC appear to be governed by the sulfate content of the CKD-PC blend (the form of the CKD sulfate is not significant). According to analysis of the ASTM expansion in limewater test results, the CKD-PC blend sulfate content should be less than ~0.40% above the optimum sulfate content of the PC. It was also found that the sulfate contribution of CKD behaves similar to gypsum. Therefore, CKD-PC blends could be optimized for sulfate content by using CKD as a partial substitute of gypsum during the grinding process to control the early hydration of C3A. The wet and long-dry kiln CKDs contain significant amounts of calcium carbonate (>20%) which could also be used as partial replacement of limestone filler in PC.

The mechanical response of geomaterials is highly influenced by geometrical and material heterogeneity. To date, most modelling practices consider heterogeneity qualitatively and the choice of input parameters can be subjective. In this study, a novel approach to combine detailed micro-scale characterization with modelling of heterogeneous geomaterials is presented. The influence of micro-scale heterogeneity and microcracks on the mechanical response and brittle fracture of a crystalline rock was studied using numerical and experimental tools. An existing Combined Finite-Discrete element (FEM/DEM) code was extended to suit heterogeneous, discontinuous, brittle rocks. By conducting grid micro-indentation and micro-scratch tests, the Young's modulus and fracture toughness of the constituent phases of the rock were obtained and used as accurate input parameters for the numerical models. The models incorporated the exact phase mapping obtained from a MicroCT-scanned specimen and the existing microcrack density obtained from thin section analysis. The results illustrated that by incorporating accurate micromechanical input parameters and the intrinsic rock geometric features, the numerical simulations could more accurately predict the mechanical response of the specimen, including the fracture patterns and tensile strength. The numerical simulations illustrated that microstructural flaws such as microcracks should be included in the models to more accurately reproduce the rock strength. In addition, the differential elastic deformations caused by rock heterogeneity altered the stress distribution in the specimen, creating zones of local tensile stresses, in particular, on the boundaries between different mineral phases. As a result, heterogeneous models exhibited rougher fracture surfaces. MicroCT observations emphasized the influence of heterogeneity and, in particular, biotite grains on the fracture trajectories in the specimens. Favourably oriented biotite flakes and cleavage splitting significantly deviated the cracks. The interaction of the main crack with perpendicular cleavage planes of biotite caused strong crack deviation and termination. Considering heterogeneity and the strength degradation caused by microcracks, the simulations captured reasonably accurate mechanical responses and failure mechanisms for the rock, namely, the nonlinear stress-strain relationships. The insights presented in this study improve the understanding of the role of heterogeneity and microstructure on damage and mechanical behaviour of brittle rock.

Minimum impact construction for bridge building is a growing demand in modern urban environments. Pre-cast segmental construction is one solution that offers low-impact, economical, and aesthetically pleasing bridges. The standardization of pre-cast concrete sections and segments has facilitated an improved level of economy in pre-cast construction. Through the development of high performance materials such as high strength fibre-reinforced concrete (FRC), further economy in pre-cast segmental construction may be realized. The design of pre-cast bridges using high-strength FRC and external unbonded tendons for cantilever construction may provide an economical, low-impact alternative to overpass bridge design. This thesis investigates the feasibility and possible savings that can be realized for a single cell box girder bridge with thin concrete sections post-tensioned exclusively with external unbonded tendons in the longitudinal direction. A cantilever-constructed single cell box girder with a curtailed arrangement of external unbonded tendons is examined.

Infiltration facilities are source control mechanisms that are implemented in urban developments with reduced natural permeable surfaces. Despite the development of design criteria for infiltration facilities, these systems continue to fail due to headloss development, overflow, or chemical breakthrough. The limited research on the long-term performance of these systems has emphasized the role of physical filtration mechanisms within porous media filters to address concerns surrounding system failure, namely filter clogging. A continuous macroscopic depth filtration model was developed to investigate the clogging potential of the underlying sand filter. This continuous model furthers the understanding of temporal and spatial changes in system performance for the development of more appropriate design criteria and more suitable maintenance regimes. The characterization of long-term system performance by defining three different failure modes and a probabilistic approach comprises a comprehensive methodology by considering several performance criteria rather than assuming that one criterion dictates the overall system performance.