Theses (Civil Engineering)

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Experimental and numerical investigation of human-induced vibration performance in mass timber office buildings
(2025) Cheraghi Shirazi, Najmeh; Malek, Sardar
Timber floors are susceptible to vibration due to their low mass and bending stiffness. Utilizing mass timber products in long-span scenarios, such as in office buildings, makes vibration an important design driver for structural engineers. The performance of long-span office floors is studied both experimentally and numerically in this thesis. First, a testing campaign conducted on two mass timber office buildings is presented. The dynamic characteristics of the floors were initially measured using hammer and heel drop tests. A series of human walking tests were also performed to assess the impact of various parameters, such as walking paths, pace rates, and walker weights, on the floor’s vibration behavior. To better understand and explain the findings in the experimental campaign, a numerical framework has been developed as a part of this research. The developed framework has been used to numerically simulate the response of a timber-concrete composite floor under human walking forces at a selected bay. The developed framework captures floor’s fundamental frequency and floor acceleration due to walking. The accuracy of the modelling framework is examined by comparing the modelling predictions with test data. It is demonstrated how the developed framework could be used as a tool to assess the impact of various boundary/connection conditions and material input parameters suggested in various design guides. In particular, the effect of parameters such as the dynamic modulus of concrete, shear stiffness of the glulam beam-to-CLT and CLT-to-concrete connectors, and the stiffness of the beam-to-beam connections (whether fixed or pinned) are investigated quantitatively. The study highlights the importance of including columns, adjacent bays, and connections between glulam beams, CLT, and concrete in the model. It is found that fixed beam-to-beam connections inaccurately predicted acceleration and overestimated stiffness and frequency, recommending pinned connections for mass timber composite floors. Additionally, the increase in stiffness from fixed connections could not be offset by reducing the stiffness of glulam beam-to-CLT and CLT-to-concrete connections. The findings from this study offer valuable insights into performance of mass timber composite floors and efficient modelling of floor vibration with complex boundary condition and connections used in practice.
Understanding and accelerating the model-based design of multi-source energy systems
(2025) Lédée, François; Evins, Ralph; Crawford, Curran
The transition towards sustainable energy system requires innovative tools and methodologies to efficiently address the design of resilient and cost-effective multi-energy systems (MES). The energy hub concept emerges as a powerful approach, capable to address optimal design and operation of energy systems while best exploiting potential synergies between technologies. Its scalability, limited by significant computational demands, is necessary to help capture the multi-scale nature of energy systems and support a harmonized transition across all levels. This thesis investigates two key strategies to leverage this limitation. The first is the use of representative days to reduce the temporal complexity of the core application. The second is the development of surrogate models to rapidly estimate optimal designs. These strategies are examined across diverse contexts and system design problems through four independent but complementary studies. Each study led to a publication in international scientific journal or conference proceedings. The first study evaluates the robustness of selection methods for the use of representative days. The study highlights their sensitivity to context and the need for validation across multiple case studies. The second study examines the impact of shorter time horizons on the MES design. It emphasizes the strong influence on the system design, particularly on the design of storage. It also offers new insights into the design decision mechanisms. The third study compares district heating and cooling technologies. It demonstrates the superiority of the 5th generation network through diverse scenarios, emphasizing sensitivity to the topology and spatial demand distribution. The fourth study develops a novel surrogate modeling framework leveraging the use of machine-learning to address system design problems. The robustness of the framework is validated across diverse scenarios. Overall, this work emphasizes the importance of context-specific validations and sensitivity analyses. These aim to improve the understanding of design decision processes of energy hub applications, necessary to develop robust and effective complexity reduction methodologies. These contributions provide a foundation to improve the scalability and accessibility of MES design methods and, eventually, support the energy transition.
Influence of soil structure and fluid physicochemical properties on surface erosion of cohesive soils
(2024) Lin, Yunjie; Lin, Cheng
Surface erosion is a process of removing soils and rocks from the ground surface, riverbeds, and seabeds by flows and currents, which pose significant threats to the safety of infrastructure and human well-being. This issue is exacerbated by global warming, resulting in increasing precipitation, rising sea levels, and the growing frequency of floods, storm surges, and hurricanes. While internal erosion has been extensively by the geotechnical community, particularly in the context of dam safety, surface erosion has een generally overlooked. In particular, a considerable gap exists in understanding surface erosion from a geotechnical perspective, especially for cohesive soils. This study aims to assess the influence of soil structure and fluid physicochemical properties on the surface erosion of cohesive soils. A custom-built Rotating Surface Erosion Apparatus (RSEA) was developed at the University of Victoria in the absence of a relevant ASTM testing standard. Extensive element-scale experiments were conducted using the RSEA to examine the erodibility of cohesive soils with varying fine contents, water contents, and stress conditions. The effects of fluid physicochemical properties on soil erosion were also evaluated. In the end, a surface erosion erodibility model for cohesive soils was proposed based on the conservation of energy. The findings of this research indicate that soil erodibility was influenced by both soil structure and fluid physicochemical conditions. An increase in the void index resulted in higher soil erosion resistance, whereas the unloading process increased soil erosion susceptibility. An inverse proportional relationship was observed between soil erodibility and the over-consolidation ratio (OCR). This relationship became insignificant once the OCR exceeded 4. Under identical hydraulic conditions, the erosion rate of natural soil was found to be 38% lower than that of laboratory-reconstituted soil. Additionally, fluid temperature was shown to primarily affect soil erodibility through physical processes, independently of pH and salt concentrations. Under low salt concentration conditions, soil erosion rates rose by up to ninefold as pH increased from 3 to 11. However, under high salt concentration conditions, erosion rates showed minimal variation with pH changes. Finally, the proposed erosion model was validated against the experimental data obtained from the RSEA, showing reasonable agreement.
Advances in reverse osmosis membrane engineering and alginate recycling: Covalent surface modifications for membrane performance and analysis of molecular changes and calcium crosslinker removal for alginate sustainable practices
(2024) Rahmati, Negar; Buckley, Heather; Basu, Onita
The increasing demand for potable water and the environmental impact of conventional plastics present significant global challenges that require innovative solutions. Addressing these issues effectively involves advancements in both water purification technologies and material sustainability. This thesis explores these challenges through two complementary projects: enhancing reverse osmosis (RO) membrane technology and improving the sustainability of alginate-based bioplastics. Reverse osmosis is a critical water purification technology used to produce fresh water from diverse sources, including seawater and brackish water. Central to this technology are RO membranes, which are predominantly made of polyamide. Despite their effectiveness, these membranes face performance limitations due to biofouling and chemical degradation. Biofouling, caused by microorganisms forming biofilms on the membrane surface, reduces water flux, increases operational pressure, and raises energy consumption. Chemical degradation affects membrane longevity and performance, leading to frequent cleaning and replacement. These issues contribute to significant economic costs and environmental waste. Chapter 1 explores the attachment of PEI-diazirine onto PET surfaces, with the hypothesis that successful cross-linking in these trials could also be applied to polyamide-based RO due to the reactivity between polyamides and carbenes. The objective was to develop a method for covalent modification of RO membranes using diazirine moieties, which could serve as a foundation for further functionalization. Covalent bonding offers advantages such as improved stability, durability, and compatibility, making it a favorable approach for RO membrane surface modification. In conclusion, the study introduced an innovative approach to enhancing the surface properties of RO polyamide-based membranes by incorporating covalently bonded diazirine-containing molecules. While direct evidence of covalent attachment was not confirmed, indirect observations—such as results from dye and water angle tests, DSC, and FTIR—support the presence of activated diazirine on the surface. These tests disproved the idea that diazirine molecules react exclusively with each other rather than with the surface. This groundwork sets the stage for future functionalization processes to impart foul-release properties to RO membranes. Chapter 2 focuses on advancing the sustainability of alginate-based bioplastics, particularly those derived from kelp. The study investigates the recycling potential of alginate, aiming to enhance sustainable practices. Recycling alginate helps preserve resources by reintegrating used materials into the production cycle, reducing the need for fresh raw materials. Additionally, recycling alginate-based products reduces waste volume, supports waste reduction goals, and minimizes the environmental impact of landfill disposal. The research in Chapter 2 builds on optimized sodium alginate extraction methods and evaluates the recycling potential of alginate films produced by these methods. It proposes and assesses a recycling protocol for its effectiveness in terms of yield and purity, focusing on calcium crosslinker removal and structural changes in alginate films. This study provides valuable insights into sustainable alginate recycling, promoting a circular economy by extending the life cycle of materials and reducing waste generation. Although each chapter addresses different material types and applications, they share a common theme: enhancing material performance while mitigating environmental impact. Improving RO membrane fouling resistance and chemical stability directly contributes to reducing waste and energy consumption in water treatment. For alginate bioplastics, optimizing recycling processes ensures effective material reuse, decreasing plastic waste and the demand for new raw materials. These projects reflect a broader commitment to sustainability by tackling critical issues in material performance and environmental responsibility. The outcomes from these chapters offer practical solutions that align with global efforts to conserve resources and minimize ecological footprints. Through the development of advanced membrane technologies and sustainable bioplastics, this thesis contributes to a more sustainable future, demonstrating that innovation in material science can drive significant improvements in both industrial applications and environmental stewardship. In conclusion, this thesis bridges the gap between technological advancement and environmental sustainability. By addressing the challenges of water purification and plastic waste management, it provides valuable insights and practical solutions that enhance material performance and promote a more sustainable approach to resource use.
Numerical study of the structural performance of strong wood light-frame shear walls under large lateral loads
(2024) Ghazinader, Dina; Malek, Sardar; Sun, Min
The motivation for this study comes from the increasing demand for safe, affordable wood-frame buildings in Canada over the past decade, primarily due to their low cost, high ductility, and ease of construction. In such buildings, wood-frame shear walls are commonly utilized as the main lateral load-resisting system to resist seismic loads. Wood-frame shear walls are typically comprised of timber framing members, sheathing panels such as plywood or oriented strand board (OSB), and fasteners like nails and bolts. The best performance of such walls is achieved when most of the energy is dissipated through shear deformation in the sheathing-to-framing connectors (i.e. nails) while the framing and anchorage systems remain in their elastic regime. This study presents the results of extensive numerical and analytical investigations into the behavior of "strong" wood-frame walls subjected to large monotonic and cyclic loads. A detailed 3D finite element (FE) model in ABAQUS software was employed for an in-depth analysis of shear wall components and to examine the impact of various parameters on their performance. The accuracy of the FE model for both the nail connectors and the wall assembly is validated by comparing its results with experimental data from the literature. Further analyses showed that the Canadian Standards Association (CSA), and the Special Design Provisions for Wind and Seismic (SDPWS) guidelines slightly overestimate the initial wall stiffness, with the discrepancy increasing at larger displacements. The numerical analyses conducted on strong shear walls with different hold-down systems show that discrete hold-down system can overstress the end studs, increasing the risk of wood crushing and brittle failure in the framing members. In contrast, continuous steel rods maintain stresses within safe limits and shift the failure mode (nail yielding) from the end studs to the center of the wall, thereby enhancing the overall structural performance. The numerical results further indicate that, although the diameter of continuous rod hold-downs does not significantly affect the wall’s strength, it plays a critical role in delaying yielding in the anchorage system, thereby improving the overall wall performance and energy dissipation under lateral loads. Numerical results also show that thicker OSB sheathing panels or materials with a higher modulus of elasticity (MOE) improves energy dissipation while ensuring the frame members and anchorage system remain within their elastic range. Thicker panels help prevent edge tear-out and nail head pull-through by reducing the crushing of wood strands in the OSB, allowing the nails to deform more before ultimately withdrawing. This suggests that optimizing the mechanical properties of sheathing panels may improve shear wall performance and energy dissipation while minimizing the need for additional nails, providing a balanced approach to enhancing both strength and ductility in the design leading to more resilient shear walls under strong earthquakes.
Experimental evaluation of the wicking and reinforcement functions of wicking nonwoven geotextile-geogrid composite in roads
(2024) Liu, Minghao; Lin, Cheng
Road performance is significantly enhanced by incorporating geosynthetics through their reinforcement and drainage functions. This study introduces a new geosynthetic that integrates all these functions. It is made of biaxial polypropylene geogrids heat-bonded to wicking nonwoven geotextiles (WNWGs). Unlike the wicking woven geotextiles comprising deep-grooved fibers, WNWGs are chemically treated to be hydrophilic and thus possess rapid wetting and wicking properties while preserving the large lateral drainage functionality of conventional nonwoven geotextiles. To assess the wicking behavior of the geotextile, a series of wicking tests were conducted in water alone and saturated soils under controlled temperature and relative humidity. Additionally, contact angle measurements and microscopic analyses with Scanning Electron Microscopy (SEM) were conducted to elucidate the underlying wicking mechanisms. To assess the combined reinforcement and wicking performance of the new composite, a series of model tests including rainfall simulation and plate loading tests were performed on the WNWG-geogrid composite reinforced bases over weak subgrade using a customized model test apparatus. The results confirmed that the inclusion of WNWG-geogrid composite significantly enhanced drainage, stiffness, and bearing capacity of road bases. The findings from this study demonstrate the promising performance of this new composite and provides valuable reference for full-scale tests and applications in roads.
Nonlinear dynamic assessment of mid-rise light-frame wood shear walls under horizontal and vertical ground motions
(2024) Mohammadi, Hadiseh; Malek, Sardar; Sun, Min
This research complements recent studies on light-frame wood shear walls for mid-rise buildings by comparing the dynamic performance of multi-story shear walls constructed with discrete and continuous rod hold-down systems. For this purpose, a numerical model has been developed and series of comprehensive nonlinear time-history analyses are conducted in SAP2000 software. Maximum inter-story drifts are estimated and compared under different earthquake records. According to the numerical results, using continuous steel rod hold-down could reduce the maximum drift in the multi-story strong wall by over 40%. The maximum drift in the strong shear wall with discrete hold-down is 2.3%, while this value is 1.3% in the wall with continuous rod hold-down. The results show the better performance of continuous steel rod leading to lower inter-story drifts in all stories in both multi-story conventional and strong wall. Estimates of deflection and drift of a six-story strong wood shear wall using CSA O86:19, SDPWS 2021, are also compared with numerical modelling results. The estimates from CSA O86:19 is found to be conservative, with deflections 10% to 55% higher than the FE model, while SDPWS 2021 generally predicts lower deflections in upper floors compared to FE and CSA O86. It should be noted that while the results indicate that the deflection predictions from CSA O86:19 may be conservative in some stories, the drift predictions might not be. According to parametric studies conducted using the development numerical model, higher aspect ratios could lead to increased axial forces in studs and hold-downs as expected, with a notable rise in tension for walls with an aspect ratio of 1.50 compared to those with 0.72. Numerical results in the walls with different numbers of stories (one, three, five and six stories) illustrate how demands are distributed vertically across different stories during an earthquake event, with the maximum force in the studs concentrated at lower story levels. Numerical results show that including vertical component of earthquake slightly increases lateral deflections and axial forces, with continuous rod systems showing smaller increases compared to discrete hold-downs. In terms of diaphragm effect, a significant reduction in lateral deflection of considered shear walls under monotonic load are noted due to out-of-plane stiffness effect of diaphragms especially at higher stories.
Communicating net-zero climate policy and energy modeling results via an interactive visualization dashboard
(2024) Attard, Erica; McPherson, Madeleine
The Canadian Government has pledged to achieve net-zero greenhouse gas emissions by 2050. To achieve this target, energy modeling is required to evaluate different decarbonization pathways and possible policy options, however, its impact is currently stunted due to a communication gap between energy modelers and stakeholders. This thesis presents the development and testing of the Integrated Dashboard for Energy transition Analysis (IDEA), an open-sourced tool used to address the communication gap and promote evidence-based decision making. IDEA enables policy makers to evaluate decarbonization pathways and complex policy decisions through the use of visualizations and an interactive dashboard. A Human Centered Design process was implemented to develop a prototype dashboard and evaluate its functionality and applications. Key stakeholders including Environment and Climate Change Canada, Natural Resources Canada, the David Suzuki Foundation, Clean Energy Canada, BC’s Ministry of Energy, Mines and Low Carbon Innovation and BC’s Climate Action Secretariate were involved in the development and evaluations. An output of this thesis is a fully tested visualization dashboard that is adaptable to multiple models and visualization types. The major contributions of this thesis include insights and guidelines surrounding the needs of stakeholders, a detailed discussion on the current and future applications of IDEA, and a call for further communication tools that can advance data-driven decision making. IDEA successfully operates as a results analysis tool, enabling modeling teams and stakeholders to evaluate complex policy decisions. Future applications include expanding IDEA to a key insights tool, supporting decision makers with the most pertinent information, and a modeling tool, allowing stakeholders to implement their own assumptions and model formulations to conduct independent evaluations. Future work includes implementing the discovered improvements to strengthen IDEA as a results analysis tool and further investigating the feasibility and impact of the other tools uncovered.
A novel approach to life cycle assessment for early-stage design of low-carbon buildings
(2024) Torabi, Mahsa S.; Evins, Ralph; Bristow, David
Building design processes are dynamic and complex. The context of a building project is manifold and depends on the context, climatic conditions and personal design preferences. Many stakeholders may be involved in deciding between a number of possible designs defined by a set of influential design parameters. Building LCA is the state-of-the-art way to provide estimates of the building carbon content and environmental performance of various design alternatives. However, setting up a simulation model can be labour intensive and evaluating it can be computationally unfeasible. As a result, building simulations often occur at the end of the design process instead of being an influential factor in making early design decisions. Given this, the growing availability of machine learning algorithms as a potential method of exploring analytical problems has lead to the development of surrogate models in recent years. The idea of surrogate models is to learn from physics-based models, here a building LCA model, by emulating the simulation outputs given the simulation inputs. The key advantage is their computational efficiency in terms of accuracy and time. They can produce performance estimates for any desired building design within seconds, while in physics based modeling hours maybe needed to run the analysis. This shows the great potential of surrogate modelling to innovate the field. Instead of only being able to assess a few specific designs, entire regions of the design space can be explored, or instant feedback on the sustainability metrics of building can be given to architects during design sessions. This PhD thesis aims to advance the young field of building LCA surrogate models. It contributes by: (a) developing a parametric model capable of whole design space exploration, to solve the issue of lack of building LCA data and (b) deriving surrogate models that can process dataset of building carbon results and estimate the associated impact on building performance. The result of this study can assist architects, engineers, researchers and policy makers both by provided results and also the proposed methodology to integrated LCA in strategic and early-stage decision making in the design process.
Traffic tracking and air quality: A holistic approach to predicting traffic-related air pollution
(2024) Deveer, Laura Ahinee; Minet, Laura
On-road transportation has long been a significant contributor to air pollution in cities. Over the past few decades, the transportation sector, which has been targeted by major regulations, has undergone substantial changes. These changes include a shift in vehicle fleet composition and both natural and artificial alterations to traffic patterns. Despite the importance of on-road transportation for urban mobility, it remains a major source of air pollution and a public health challenge. Therefore, it is essential to accurately measure and model the temporal and spatial distribution of traffic-related air pollution. In that way, targeted implementations can be made to combat the adverse health effects associated to the exposure to these pollutants. In this thesis, we investigate the potential of low-cost methods to accurately estimate air pollutant concentrations. To this end, we employed modern traffic tracking technologies with low-cost sensors and machine learning techniques. The research addresses the effectiveness of leveraging these technologies to understand the factors and interactions that influence air quality. Chapter 2 predicts real-time air pollutant concentrations with high accuracy across pollutants using traffic videos and machine learning algorithms. The results reveal the superior performance of non-linear models over linear models. In addition, the Shapley additive explanation plots employed in this study effectively captured the intricate relationships between pollutants and their predictors. Chapter 3 examines the influences of traffic, particularly from cruise ship activities, on local air quality in James Bay, Victoria, BC. Results indicate that both emissions from traffic and cruise ship activities affected air quality. The integration of low-cost sensors with these traffic tracking technologies proves crucial for accurate air quality analysis and allows for context-specific and real-time assessments, providing valuable insights for policy makers and urban planners.
Load tests and numerical modeling of CFA and driven piles in marl in Savannah, Georgia
(2024) Zhou, Zhihao; Lin, Cheng
Marl along the southeast coast of the US, especially in South Carolina and Georgia, is a stiff, calcium carbonate-rich, over-consolidated fine-grained soil commonly used as a bearing layer for pile foundations. However, two significant engineering challenges arise: unreliable CPT-based estimations of pile resistance and strain-softening behavior complicating the prediction of pile capacity, deformation, and load-transfer mechanisms under axial load. Comprehensive pile load tests conducted in Savannah, Georgia, were used to improve CPT-based pile resistance estimations and develop a numerical model using load-transfer (t-z and Q-z) method for driven and Continuous Flight Auger (CFA) piles. For CPT-based pile resistance estimations, the accuracy of the original LCPC and Eslami and Fellenius methods was first evaluated. Pile load test results were then used to back-calculate the coefficients of these methods for improvement, which were subsequently verified with additional pile load test data. The main strength parameters of the load-transfer (t-z and Q-z) method model were correlated with the improved CPT methods coefficients. After calibration, the numerical model was verified using additional pile load test data. Moreover, a 3D continuum finite element method (FEM) simulation using the ‘OC Clay’ model in Plaxis 3D was conducted to capture strain-softening behavior and examine load-transfer mechanisms. The 3D continuum FEM model was calibrated and validated against separate pile load test data, and a parametric study was conducted to investigate how soil strength parameter, pile dimensions, and embedment depth into marl influence pile performance.
Seismic evaluation of high-capacity shear walls used in mid-rise light wood frame buildings
(2024) Shameli Derakhshan, Shervin; Zhou, Lina; Ni, Chun
The primary construction method for single-family homes and low-rise multi-family residences in North America is characterized by the prevalent use of light wood framing. The increasing urban population and the imperative to achieve sustainability goals demand permitting taller structures in regions previously marked by low-rise building practices. Since 2009, the Building Code of British Columbia has raised the storey limit of residential light wood frame buildings to 6 storeys. Adopting the same approach, in 2015, the National Building Code Canada (NBCC) also allowed the design and construction of wood-framed buildings up to 6 storeys. The increase in height leads to more flexible structures, potentially necessitating a more robust shear load-resisting system. While light wood frame structures have, by and large, performed well during earthquakes, the evolution in construction practices creates additional demand on the lateral load-resisting system. This calls for innovative designs that boost the lateral resistance of light wood frame shear walls, especially for buildings located in high seismic zones. The seismic force-resisting system of light wood frame buildings consists of studs, sheathing panels and fasteners, which are usually nails. This system is commonly known as light wood frame shear walls. In order to enhance the seismic performance of light wood frame buildings, modifications need to be made to the conventional shear wall system. This dissertation explores the implications of a novel light wood frame shear wall named High-Capacity Shear Wall (HCSW). The introduced HCSW has two rows of fasteners along sheathing edges. Through comprehensive analyses, this research adopts a testable approach to the investigation of HCSWs under seismic loads. This research program consists of three parts. The first part of the study addressed the effect of the loading protocol (namely ISO, CUREE, and SPD) and loading rate on the characteristics of timber nail joints. Since nail joints are one of the key components that control the lateral performance of light wood frame shear walls, it is of paramount importance to determine how different loading rates and protocols can influence the mechanical properties of the system. Accordingly, 96 nail joint samples were tested under monotonic and reversed-cyclic loading. The findings of this part of the research laid the foundation for the reversed-cyclic loading testing program of HCSWs, which is the second part of the study. The second part of this research study delved into evaluating the seismic performance of HCSWs through conducting full-scale experiments. The experimental program consisted of 10 full-scale shear walls (9 HCSWs and 1 standard shear wall), and the test matrix included specimens with different sheathing thicknesses, nail diameters, and nail spacing. Test results showed that HCSW had 1.8–2.0 times the lateral load resistance of a standard shear wall (also known as the regular shear wall) with the same sheathing thickness, nail diameter, and nail spacing. The initial stiffness and ultimate displacement of the HCSWs were also greater than those of the comparable standard shear wall. Based on seismic equivalency criteria, shear walls with two rows of nails (i.e. HCSWs) could be assigned a design value of the comparable standard shear wall multiplied by a factor of 1.7. In the last part of the study, the seismic performance of light wood frame buildings with HCSWs was investigated. The full-scale reversed-cyclic loading test results revealed that the ductility ratio of some HCSWs could be lower than that of the regular wall based on the ASTM D7989 method. This method is in fact a simplified and straightforward method for assessing the behaviour of light wood frame shear walls. Thus, a more comprehensive seismic evaluation can employ the time-history analysis of buildings following available guidelines. Consequently, the seismic performance of 1-storey and 6-storey light wood frame buildings under 12 archetypes undergoing 22 ground motions suggested by FEMA P695 was evaluated. Incremental Dynamic Analysis (IDA) was performed to evaluate the collapse capacity of archetypes. Also, the effect of initial stiffness on collapse margin ratios (CMRs) and maximum inter-storey drifts (MISD) at the design level was studied. The results showed that utilizing HCSWs improved the collapse capacity of both low-rise and mid-rise buildings. Models with HCSWs demonstrated larger CMRs (with a maximum of 2.47). Additionally, it was observed that the increase in initial stiffness could reduce the MISD at the design level as low as 0.42%. The findings of this study prove that the use of HCSWs enhances the seismic capacity of light wood frame buildings (using the same R_d and R_o factors of regular shear walls) in regions of high seismicity.
Examining the performance change of inverse surrogate models with building energy model time series data
(2024) Jowett-Lockwood, Liam; Evins, Ralph
A building Surrogate Model (SM) is a Machine Learning (ML) model trained to reproduce the outputs of a building energy model at a much smaller computational cost. While a SM will traditionally accept Building Energy Modelling (BEM) parameters for its inputs to predict BEM outputs, a building Inverse Surrogate Model (ISM) suggests doing the opposite. Inverse modelling provides potential in determining unknown building thermal characteristics of existing structures. The task of deriving inputs from outputs is more difficult as multiple input combinations can result in the same output, thereby necessitating the need for comprehensive outputs allowing for more information to be extracted. With the rise of deep learning models and methods, ML practitioners have a greater array of tools available to handle increasingly complex tasks. This has enabled ISMs with a stronger opportunity to excel in parameter prediction. The papers in this thesis focus on the ability of the ISMs to accurately predict parameter values. The first paper (Chaper 2) examines prediction performance of an ISM with synthetic data from a BEM model based on a single-family home. Performance changes were investigated when data was decreased by reducing the amount of time series provided, the duration of time series, or both. The second paper (Chapter 3) primarily focused on the generalizability of ISMs to be applied for multiple projects without having to retrain on new data each time. Several different ISM models were tested with predicting parameters for different BEM building shapes with varied geometry in addition to multiple locations. The key finding of this research is that there is potential for ISMs to be used with building data. While all data used in this thesis was synthetic data generated from BEM simulation runs, ISMs were shown to not only successfully predict some parameters, but also hold solid degree of generalizability depending on the ML model used. If ISMs can successfully predict characteristics of an actual building, then it allows for new approaches for applications such as retrofit planning.
Canada’s power system toward zero-emission targets, planning, operation, and flexibility options
(2024-01-10) Miri, Mohammad; McPherson, Madeleine
Canada has targeted to reduce carbon emissions in the power system by 30% until 2030 compared to 2005 levels. Zero-emission is also targeted for 2050. Many transition pathways can be followed to achieve these targets and are being followed by various regulations. One of the main paths is to incorporate variable renewable energy resources as high wind and solar irradiation potentials are proved Canada-wide. At the same time, other sectors are targeting similar targets which are mainly followed through electrification. Variability inherited from large wind and solar capacities and demand growth and change through electrification burdens power systems from both supply and demand sides. Flexibility is a requirement for the power sector to operate reliably to match variable wind and solar capacities with fluctuation and growing demand. Therefore, flexibility should be considered by policymakers when analyzing the transition toward a decarbonized power system. This thesis proposes linked frameworks to analyze flexibility issues in the outlined generation portfolios and to study a variety of power system flexibility options on the supply and demand sides. Two different frameworks are developed to interlink the power system capacity expansion planning model, production costs model, and building sector energy simulation model. These frameworks are also applied to analyze effectiveness and impact of the different flexibility options impacting various components of the power system, supply side, network, and the demand side. In the first iteration, flexibility issues stemming from the transmission system and shortage of storage systems are analyzed in an iterative interlinked model. In response, transmission expansion as costs and supply-side storage capacities as minimum constraints are fed to the expansion planning model. Results show that there are several flexibility issues uncovered by the technically detailed operational model. These issues are resolved by adding transmission and storage capacities to the system, posing the system extra expansion costs to reach a certain level of flexibility. The overestimation of the wind capacities is corrected when accounting for the transmission requirements. In the second iteration, the generation portfolio is outlined by various scenario inputs for electrified and non-electrified demand, and for zero-emission and non-capped emission scenarios. The outputs are analyzed in the operational model using a one-way linked data transfer for flexibility issues. Impacts from demand-side flexibility options, i.e., demand response, are analyzed using an iterative linked loop between the building sector energy simulation model and the operational model. The results show that the demand response programs have a significant impact on flexibility concluding to integrating more generation from wind and solar capacities. It is shown that a realistic representation of the impacts of demand response on the demand curve can cause some limitations in implementing demand response programs. Compared to supply-side options, demand response is discussed to require lower investment requirements to be implemented and even reduce the need for capital-intensive options on the supply side, like transmission and storage. In the last iteration, the integration of power systems is considered a flexibility option and assessed through the one-way linked framework of expansion planning and operational model. Input scenarios for transmission cap for systems’ integration and electrification in the demand are considered to be the most impactful variables in this study. The results show significant savings in costs and electricity prices by integrating the two selected power systems of Alberta and British Columbia. It is also shown that with the better overall flexibility of the integrated systems, more wind and solar generation can be integrated into the generated output. As hydro is discussed to improve flexibility, the analysis shows that climate change effects on the must-run requirements can impact the efficiency of the delivered flexibility. Investigating various variables in the transition pathways and their impact on the power system during this thesis shows that there are requirements that should be met in the system in order to maintain the reliability and efficiency of the projected paths. Three different flexibility options is analyzed that fulfill these requirements which showed different impacts on expansion planning and operation of the system in terms of costs and their effectiveness to integrate VRE integration. While supply-side options like storage and transmission expansion options impose additional investment costs, power systems can benefit from lower costs of demand-side options as well as reducing supply-side requirements. Integration as the third option has also proved to have a substantial impact on the enacted costs of transition pathways as well as delivering flexibility. These options ranked in terms of implicated costs and their effectiveness as a high-level conclusion as: power systems integration, supply-side options, and demand side options.
Novel method for electrically tuning the resonant frequency of Piezoelectric Vibration Energy Harvester (PVEH) by using low power actuation
(2024-01-10) Raghavan, Sreekumari; Gupta, Rishi
Advancements in electronics and MEMS (Micro Electro Mechanical Systems) technology have enabled the deployment of a large number of sensors and signal transmitters on structures at critical locations to extract vital data and avoid catastrophic failures. This approach leads to condition- based maintenance of structures. In this scenario, the critical requirement is an autonomous power source that can power the system. In most cases, wired connections to a central power unit are not feasible, resulting in the use of batteries to power the sensors and transmitters. In recent years a great deal of research has been focused on harvesting from solar, thermal, kinetic, and RF (Radio Frequency) energy available in the environment. Of all these ambient conditions, kinetic energy in the form of vibrations is more prevalent in many structures and machinery. This has resulted in an increased focus on effectively converting vibration energy to electrical energy. Among many methods adopted, the application of piezoelectric materials has led to promising results. A piezoelectric energy harvester in a cantilever design can generate high power output, only at its resonant frequency and much research has been focused on methods of tuning the harvester to match the ambient frequency of vibrations. This dissertation details an active tuning methodology and design of a device, which has resulted in achieving a net power gain. The concept is to utilize a low power actuation mechanism integrated with the harvester to enable active tuning of the resonant frequency of the device. The approach was to make use of Ionic Polymer Metal Composites (IPMC) for the required actuation. IPMC is a smart material, whose actuation can be altered by varying the input voltage to the device. The IPMC used here is perfluorinated Nafion films with noble metal coated on both sides as electrodes. When subjected to an applied voltage, the free cations in the membrane, tagged to the water molecules, move to the negative electrode. This phenomenon creates bending of the film. This is the actuation process associated with IPMC. The actuator unit of two strips of IPMC, attached at the tips was powered by a very low voltage ranging from 1 to 4 V. The various levels of actuation generate corresponding block forces and functions as equivalent to tunable stiffness stoppers. This dissertation provides details of experiments carried out, theoretical analyses, and the applications of this novel device.
A Novel Methodology to Predict the Long-Term Performance of Vacuum Insulation Panels (VIPs) Using Climate Data
(2024-01-05) Van Es, Jonathan; Mukhopadhyaya, Phalguni
Vacuum insulation panels (VIPs) have been a common insulating technology used in refrigeration and can help limit energy use in buildings by providing up to 10 times more insulation than typical insulation materials, all while using less wall space. This is specifically useful in places like Canada, where climates are cooler. Knowledge gaps around aging have currently prevented VIPs from being used in building envelope constructions. One of the remaining gaps of knowledge is that there is no methodology that has been created and linked to climate data to predict the actual performance of VIPs. This paper starts with discussions on various factors which influence the thermal conductivity of a VIP, relates it to the climate data of Victoria, British Columbia, Canada from 1997-2021, and proposes a methodology that can predict the long-term performance of VIPs in different climates. The proposed methodology was created in a piecewise approach, starting from constant conditions of 23 ֯C and 75%RH, moving to dynamic conditions based on climate data, and then adding the presence of a getter and desiccant. The resultant methodology produced a simplistic approach that has the potential to predict the performance of VIPs in various climate conditions. The proposed methodology shows that the thermal conductivity of VIPs remained relatively constant until either the getter or desiccant reached capacity. From there, the thermal conductivity began to increase over time. This methodology was then applied across four other (total of five) Canadian cities (Victoria, BC; Edmonton, AB; Yellowknife, NT; Ottawa, ON; Quebec City, QC), which all showed similar aging trends except for Victoria, British Columbia when reviewing ageing due to moisture content and Yellowknife, NT due to air pressure. The outputs from this methodology were also compared to the results obtained from accelerated ageing tests conducted in the laboratory, to estimate VIP parameters such as air and water vapour transmission rates, desiccant quantity, and sorption characteristics of the core material. The refined methodology can be converted into a standard method that has the potential to accurately predict VIP ageing in different climatic conditions.
The balancing act of renewable transitions: Modelling demand response programs to facilitate variable renewable energy integration at the city-scale
(2023-12-22) Seatle, Madeleine; McPherson, Madeleine
Evolving technologies and ambitious decarbonization policies require a shift away from carbon intensive fuels and, if the electricity grid is decarbonized, the path forward is heavily reliant on electrification. Besides the effectiveness in emission reduction, electrification offers opportunities to increase grid flexibility through programs such as demand response (DR). Despite being widely seen in literature that DR programs are beneficial to the grid, there are limited, if any, DR programs available. As DR programs span sectors, building and transportation demand models are linked with an electricity system model for the purpose of determining the viability of city-scale decarbonization policies, in which DR programs play a role. Further, this work outlines two approaches to modelling DR programs, iterative and non-iterative. The iterative approach is found to be a viable option for situations where scenario feasibility is being assessed, though the solution may end up being non-optimal. In contrast, the non-iterative approach is found to be effective at assessing the value of DR to the grid and to the consumer as the optimal solution for the scenario is determined. Key insights from this research extend further than the Canadian context; as decarbonization is an urgent goal at the global scale, these modelling approaches can be applied to any international jurisdictions considering leveraging the advantages of DR programs.
Multiphase Characteristics of Carbon Fiber-Reinforced Cementitious Materials Under Static and Freeze-Thaw Cyclic Loading Conditions
(2023-11-24) Monazami, Maryam; Gupta, Rishi
Aging concrete infrastructure, particularly in colder climates like Canada, demands urgent maintenance and renewal due to the severe temperature variations. These conditions lead to issues such as cracking, spalling, and overall deterioration. To ensure the longevity and functionality of infrastructures, it is crucial to use durable and high-performance materials. Adding fibers to the concrete mix can improve its toughness and resistance to cracking. Fiber-reinforced concrete (FRC) can withstand higher tensile stresses and distribute loads more effectively, increasing the overall durability. Among various types of fibers, carbon fibers (CFs) have gained significant popularity due to their unique ability to confer self-deicing properties to cementitious materials. This characteristic holds particular importance in colder climates, where maintaining safe and accessible infrastructure, during harsh winter conditions is paramount. Carbon fiber-reinforced concrete (CFRC) has various advantages over normal concrete, including self-deicing, high strength, durability, and corrosion resistance. CFRC's self-deicing capability is achieved through the electrical conductivity of CFs, which allows an electric current to be applied to generate heat and melt ice or snow. This feature improves safety by preventing icy surface conditions and lowers maintenance costs for snow removal and deicing chemicals. CFRC is also highly durable and strong, making it suitable for infrastructure and architectural construction. Additionally, its resistance to corrosion ensures long lasting performance and extends the lifespan of CFRC structures. Integrating self-deicing CF reinforcement within concrete bus pads offers a practical approach to leverage their inherent self-deicing property, resulting in heightened passenger safety and convenience throughout the winter season. With CFs generating heat to melt accumulated ice and snow, the bus pads retain a snow-free surface, thereby mitigating the potential for slips and accidents among passengers and pedestrians. This endeavor directly fosters a transit environment that is safer and more accessible. While numerous studies have studied self-deicing characteristics of CFRC in colder climates, a notable research gap exists in examining how CFRC responds to the rigorous challenges of freezing and thawing (FT) cycles. Despite the extensive exploration of CFRC's ability to melt ice and snow, the absence of investigations into its deterioration behavior under cyclic freezing and thawing conditions is a critical oversight. This dissertation aims to fill the existing knowledge gap and challenges related to the performance assessment of CFRC under cyclic freezing and thawing loading conditions, as well as introducing an optimized mix design for concrete suitable for colder climates. The research methodology involves a comprehensive investigation that incorporates both destructive and non-destructive testing techniques. It is clear that a multitude of pertinent factors, encompassing factors such as fiber and aggregate type, fiber length, cement paste composition, and different admixture can have significant impacts on the performance of cementitious composites. Within the context of this dissertation, however, the study has meticulously centered its investigative on carbon fiber's physical properties and its concentration. In the pursuit of refining the mix design to attain optimal outcomes, the research engaged in an array of destructive analyses, including compressive strength tests, splitting tensile strength tests, and flexural strength tests. These tests provide insights into the strength and structural behavior of CFRC under FT conditions, allowing for an evaluation of its performance. In conjunction with conventional destructive tests, this research integrated non-destructive testing (NDT) methodologies to appraise the structural integrity and quality of the CFRC specimens. Employing advanced techniques including ultrasonic testing, rebound hammer analysis, and ground-penetrating radar, a comprehensive evaluation was systematically conducted on CFRC samples subjected to an extensive and rigorous regimen of 300 FT cycles. Throughout this demanding exposure, the samples underwent the complete array of non-destructive assessments at regular 30-cycle intervals. This approach was undertaken to meticulously discern and analyze the cumulative deteriorative effects that emanated from the repetitive FT cycles. These insights yielded a profound understanding of the durability performance of CFRC under the persistent challenge of FT conditions. The synergistic integration of both destructive and non-destructive testing methodologies yields a holistic and nuanced comprehension of CFRC performance in areas with colder climate such as Canada. This assimilated knowledge stands as a pivotal cornerstone for the formulation of an intricately optimized mix design, one fortified to effectively withstand the challenges imposed by cyclic FT cycles. The research outcomes have the potential to contribute to the advancement of CFRC technology, enabling its effective use in regions with colder climates and facilitating the construction of durable and resilient infrastructure in such areas. The dissertation is divided into three milestones, each with its own set of objectives and tasks, to systematically address the research questions and challenges related to CFRC. Milestone 1 encompassed a comprehensive evaluation of mechanical properties and physical properties in different carbon fiber types, emphasizing a comparative analysis on commonly used CFs. The research extended to a novel bitumen-based carbon fiber (BBCF) from Alberta, seeking to understand its microstructure and potential for market adaptability. Techniques such as scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy, along with mechanical and electrical tests, were incorporated to assess the behavior of different types of CFs. Milestone 1 also presented a novel method using a supplementary cementitious materials (SCM) fiber coating technology. This breakthrough improved the interfacial transition zone (ITZ) between fibers and the cement matrix, resulting in improved composite performance. The goal of this milestone was to meticulously compare and establish correlations between the diverse properties exhibited by various fiber types. This systematic investigation attempted to identify the best fiber choice for incorporation into cementitious materials, thereby improving the cementitious composite's overall performance. Milestone 2 shifted the focus to investigating the mechanical and fracture behavior of carbon fiber-reinforced cementitious composite (CFRCC) and the interrelationship between materials properties and mechanical performance. A systematic approach for Laboratory testing and structural analysis has been presented in this milestone. Uniaxial tension tests were performed on dog bone-shaped Carbon Fiber Reinforced Mortar (CFRM) to analyze the behavior of samples subjected to axial tensile forces. Flexural characteristic of CFRC samples is key parameter that involves composite behavior under bending loads. While flexural testing often employs beams, it may not effectively represent the performance of fiber reinforced concrete due to considerable differences in cracking behavior of FRC with normal concrete. This discrepancy is particularly noticeable in slab and pavement applications, owing to the substantial variability in flexural behavior observed in Fiber-Reinforced Concrete (FRC) beams. Additionally, the smaller fracture area resulting from a lower count of fibers further compounds this distinction. During this milestone, a thorough and comprehensive analysis was conducted, focusing on the flexural strength of both round panels and beams. The flexural failure observed in round panels closely emulated the behavior seen in structural slabs, aligning with the principles of the yield line theory. The characterization of flexural behavior involved toughness indices and key flexural strength parameters, including bending strength and modulus of elasticity. This analysis process ultimately led to the identification of an optimal mix design. This finding underscores the significance of fiber content in influencing the overall behavior and performance of CFRC composites. Furthermore, to compare the experimental results of CFRC beam and panel flexure behavior, an analysis of variance was conducted. This statistical examination unveiled a notable 41% discrepancy in flexural properties between the two distinct sample geometries. This observation highlights the importance of considering sample geometry when assessing the flexural behavior of CFRC materials. Milestone 2 also involved a meticulous investigation into the FT behavior of the CFRC samples, evaluating their durability under the stress of 300 FT cycles. By studying the FT performance of the CFRC samples, the research aims to gain insights into the durability and resistance of CFRC to the effects of FT cycles, which can include cracking, spalling, and degradation. This information is valuable for assessing the suitability and long-term performance of CFRC in colder climates, where FT cycles are a significant concern. In Milestone 3, a case study was conducted to evaluate the durability of an electrically conductive CFRC bus pad. The case study involved integrating sensors within the bus pad to monitor factors such as strain, temperature, and moisture content. The goal was to assess the performance and behavior of the CFRC bus pad in real-world conditions. The research project aimed to gain insights into the structural integrity and durability of the CFRC bus pad by continuously monitoring its performance using embedded sensors. These sensors provided data on factors such as strain, temperature variations, and moisture content, allowing assessment the material's response to environmental influences. The study also focused on understanding how the CFRC bus pad performed under different operating conditions and evaluate its ability to withstand environmental factors. The primary objective of the research project in this milestone was to conduct a comprehensive performance assessment of CFRC bus pads, encompassing both short-term and long-term evaluations. Through this assessment, the study sought to gain profound insights into the behavior and durability of CFRC bus pads. The findings derived from this significant milestone played an important role in enhancing the design and performance of CFRC materials, ensuring their suitability for practical applications such as bus pads. Moreover, these findings hold the potential to inform and shape future advancements in electrically conductive CFRC materials for various other purposes
Evaluation of subchronic chemical exposure and risks related to regulated disinfection by-products in drinking water distribution systems
(2023-11-24) Carabin, Anne; Dorea, Caetano; Rodriguez, Manuel
The practice of disinfecting potable water is widely accepted as a way of reducing the risk of waterborne infections. This practice, however, may also result in the formation of numerous compounds known as disinfection by-products (DBPs). Among the DBPs produced by chlorination of organic matter, trihalomethanes (THM4) and haloacetic acids (HAA5) are the most prevalent families in terms of occurrence and concentration. Toxicological and epidemiological studies, reviews and meta-analysis have investigated associations between those DBPs levels/exposure and carcinogenic effects and adverse reproductive effects with different findings. The occurrence of THM4 and HAA5 is determined based on regulatory quarterly sampling for many utilities where DBPs levels fluctuate along the year and more specifically during warmer months. Hence, there is a need to investigate how this variability during warmer months can impact DBPs subchronic exposure and the associated risks. To answer to this knowledge gap, this dissertation aims to highlight the importance of taking higher seasonal concentrations into account in regulatory frameworks. It also seeks to investigate subchronic exposure and risks, as well as evaluating alternative techniques for preventing the emergence of such peaks in the warm summer months. The dissertation begins with a literature overview of DBPs health effects and a perspective paper that recommends re-examining some critical aspects of DBP risk assessment mostly related to subchronic exposure. Secondly, using an extensive dataset covering those warmer months of high variability, spatial and temporal variability of regulated DBPs were investigated in a middle-sized municipality. In order to assist stakeholders in limiting concentration peaks in the network, a model as well as an alternative technique, known as incremental differential UV-VIS, were evaluated for the first time throughout a distribution network. Furthermore, investigations were conducted to determine how this variability would affect exposure estimates and TCM subchronic risks when sampling is performed on a weekly or monthly basis. Disinfecting water is an essential public health measure, and since many people are exposed to DBPs, there is a strong need for the intra-seasonally spatial and temporal variability to be incorporated into DBP risk assessments, even if some relative health risks are small.
Climate Change Adaptation: Scenario Modelling and Insights into the Energy-Water-Land Nexus
(2023-11-06) Awais, Muhammad; McPherson, Madeleine
Climate change involves complex interactions with various sectors, such as energy, water, land, and socio-economic systems. To achieve the global warming target of "well below 2°C," the international community must address Sustainable Development Goals (SDGs) such as clean energy, water and sanitation systems, and food security. A multi-sector perspective is crucial for developing sustainable policies. Integrated Assessment Models (IAMs) are essential for analyzing long-term consequences of diverse socio-economic trajectories and climate change scenarios. However, IAMs may not fully capture the intricacies of adaptations at the local or national level. Understanding adaptation and its interaction with mitigation strategies is crucial for developing successful climate strategies. Quantitative assessments of adaptation are crucial for understanding vulnerability and providing an incomplete picture of the overall climate challenge. Using the MESSAGEix Integrated Assessment Framework, this thesis explores the capability of the IAM to address adaptation using the Indus River Basin as an example and the adaptation of the river under socio-economic, energy, water, and land resource constraints. It allows us to understand the challenges associated with formulating scenarios addressing climate impacts and adaptation. The thesis then builds upon this foundation by introducing a novel framework developed at a global level, the MESSAGEix Nexus. This framework integrates the water sector with existing energy and land systems at high spatial resolution. In addition, it includes biophysical climate impacts throughout the Energy-Water-Land (EWL) nexus using the outputs from Climate Impact Models. This framework is designed to be scalable and open-source and has already been applied at the country scale for Zambian EWL nexus analysis. In a multi-model comparative analysis, the common scenarios from the MESSAGEix-Nexus model and the IMAGE IAM are compared to look more closely at how adaptation and mitigation work together and against each other. This analysis also presents the concept of a "Climate Resilient development scenario," which, while recognizing the effects of climate change, emphasizes adaptive capacities in the context of sustainable development objectives and highlights the central role of the water system in climate change assessments.

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