Theses (Civil Engineering)

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    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.
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    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.
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    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.
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    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.
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    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.
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    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
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    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.
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    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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    Experimental Study of Shear Resistance and Failure Behavior of Reinforced and Un-reinforced Notched Cross-Laminated Timber Plates
    (2023-10-06) Goodarzi, Azadeh; Malek, Sardar; Tannert, Thomas
    This thesis presents a comprehensive experimental investigation aimed at gaining a deeper understanding of the shear resistance and failure modes of un-reinforced and reinforced notched Cross-Laminated Timber (CLT) plates. It addresses the limited availability of experimental data on notched CLT by exploring the structural behavior of notched CLT plates with and without reinforcement. A total of 174 CLT plates with various notches and reinforcement using self-tapping screws (STS) were tested in bending in both major and minor strength directions. Un-notched CLT beams under bending primarily failed in rolling shear in the transverse layers. Notches influenced not only the failure mode but also shear resistance and crack propagation. STS effectively increased the shear resistance of notched plates, with inclined screws showing slightly higher resistance compared to vertical screws. By reinforcing the notches located within the lowest transverse layer in CLTs oriented in minor strength direction, shear resistance of the corresponding un-notched plates could be attained. However, for notch ratios above 35% in those CLTs, only approximately half of the un-notched plates' shear resistance could be achieved by reinforcement. The findings offer insights for engineers involved in designing notched and reinforced CLT plates and can contribute towards developing future design guidelines for notched CLT plates.
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    Assessing Point of Use Water Treatment Technologies under Real-Use Conditions: The Field Challenge Test Technique
    (2023-09-28) Zimmer, Camille; Dorea, Caetano
    Point of use water treatment (POUWT) technologies can be the final and sometimes only barrier against waterborne illness in contexts where there is insufficient access to a safely managed on-premises water supply. Microbiological effectiveness of POUWT devices is currently evaluated under controlled laboratory conditions using water spiked with virus, bacteria, and/or protozoa or their surrogates to measure log10 reduction values or LRVs, in a process called challenge testing. However, laboratory-based POUWT challenge tests do not adequately assess microbe reduction under real-use conditions, thus omitting variations relative to factors such as user behaviours and water quality. The overall aim of this work was to develop a method with which POUWT technologies can be evaluated under real-use conditions, which we refer to as the field challenge test technique. To this end, we validated the use of probiotic Escherichia coli (E. coli Nissle, EcN) and S. cerevisiae (baker’s yeast) as field-appropriate, food-safe surrogates for pathogenic bacteria and protozoans, respectively. We implemented the innovative field challenge test technique using validated EcN and S. cerevisiae surrogates. In summer 2021, 144 one-on-one surveys were conducted of backcountry campers in the Juan de Fuca provincial park in British Columbia, Canada. The field challenge test consisted of spiking a 1 L sample of water with EcN and S. cerevisiae and requesting participants to treat the spiked water as they normally would, using their own POUWT device. Post-treatment water samples were enumerated in comparison to the original spike to calculate LRVs. Using field challenge testing, we were able to ascertain the performance of POUWT methods under real-use conditions. Our field-based LRVs were generally lower than claimed by POUWT device manufacturers for the bacterial microbe class, but for the protozoan microbe class, LRVs were similar to those claimed by manufacturers. Using the framework of quantitative microbial risk assessment (QMRA), we quantified and compared health risk estimates when using laboratory-gathered vs field-gathered LRVs of POUWT devices. Health risks attributable to the bacterial pathogen class were higher based on field-gathered LRVs (i.e., obtained by field challenge testing) in comparison to corresponding manufacturer-claimed LRVs.For the protozoan pathogen class, calculated health risks were similar due to homogeneity between field-obtained and manufacturer-claimed LRVs. The field challenge technique and corresponding QMRA analysis have numerous implications, including validation of POUWT sanitary inspection criteria, quantifying health impacts of contextual factors, or to inform technology selection.
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    Building Demand Response and the Electric Grid: Development and Application of an Operational Cross-Sectoral Model of Building-Side Electrification and Supply-Side Renewable Energy Integration
    (2023-09-22) Stanislaw, Lauren; McPherson, Madeleine
    Towards the goal of a decarbonized future, electrification of building heating systems provides both a challenge and an opportunity. Meeting additional electricity demand without increasing the associated emissions requires additional renewable capacity, but sources such as wind and solar are weather-reliant and unpredictable, making it difficult to ensure that sufficient generation is available at every instant. However, through demand response, during which buildings are subject to utility control through technology such as smart meters, building thermal mass can be used as a form of energy storage, and building demand curves can be influenced to better match the timing of variable renewable generation. In this thesis, the tension between these two aspects of building electrification is explored through the development of a novel linked model framework in which operational building and electricity system models transfer information back and forth during model setup and parameter specification steps, allowing exploration of how building system electrification impacts electricity system variable renewable expansion, and vice versa. Demand response is represented through two iterations of model development, first by changing building temperatures based on the presence of renewable curtailment (excess generation), and then by quantifying the amount of energy able to be stored in the building system during demand response events, ultimately allowing building demand response to be scheduled within the electricity system model at times that are optimal for the electric grid. This methodology is an important contribution to the literature because of its ability to represent both the supply (electric grid) and demand (building stock) sectors in operational detail, in contrast to many existing models which tend to focus only on a single sector. As well, this thesis’ case studies into residential demand response are particularly insightful given the lack of residential demand response policies in Canada today. Important results of this work indicate that increased efficiency of envelopes and heating systems can effectively limit electricity demand increases associated with increased penetration of electric heating technology, and that building demand response can effectively help cities reach their decarbonization goals.
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    (2023-08-14) Birdsell, Blair; Evins, Ralph
    This work spans multiple disciplines to focus on innovation in data-driven decision-making in building performance, utilizing machine learning algorithms. It provides performance benchmarks and analysis that can guide industry best-practice in building design and operations. Specific outcomes from this work have broad application such as the optimization of building energy efficiency, bettering occupant comfort, potential energy saving retrofits, and improving overall building performance. Data-driven decisions are made by evaluating and comparing data from various sources, including building simulations, historical records, and sensor measurements. Through the application of machine learning tools, this data is transformed into a foundation for effective decision-making by building designers and operators or incorporated into intelligent building management systems. Gradient Boosted Trees when applied to building energy performance demonstrated robust prediction characteristics across different data types and problem configurations as well as being highly accurate and computationally efficient. In predicting building performance time series, the research documents neural network architectures containing convolutional layers as having the ability to forecast short-term high-frequency variations in airflow and predict monthly minimal and maximum airflow values with high accuracy. These results support their inclusion and application in building management systems for high-performance smart buildings.
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    Seismic assessment of a hybrid light wood-frame structure connected to a balloon-type CLT core
    (2023-08-01) Eini, Ariya; Zhou, Lina; Ni, Chun
    Light wood-frame structures are the most common type of construction for residential and low-rise buildings in North America. The 2015 edition of the National Building Code of Canada has increased the height limit for light wood-frame construction from 4 to 6 stories. With the increase in building height, the design of light wood-frame structures may be more likely governed by inter-story drift under wind and seismic loads. To reduce the inter-story drift, a hybrid system, consisting of CLT cores and light wood-frame structures, is proposed in this study. Given the lack of design guidelines on the performance of hybrid wood structures under seismic loads, it is imperative to gain a comprehensive understanding of their performance under earthquake load that includes the hybrid performance, as well as performance of individual sub-structure and inter-structure connections. The first part of this study focuses on assessing the influence of energy dissipation due to different pinching levels on the seismic performance of individual sub-structure, i.e., a light wood-frame shear wall system, over a wide range of fundamental periods. The study revealed that structures with periods less 0.7 s are more susceptible to the effects of hysteresis loop pinching than long-period structures. The residual strength of pinching loops has a greater influence on the seismic performance than the stiffness of the pinching loops. Hysteretic energy dissipation derived from standard reversed-cyclic tests can provide a better understanding on the seismic resistance of timber structures. However, the hysteretic energy under a seismic event at near-collapse stage neither agrees with quasistatic cyclic test’s energy dissipation nor is well correlated to the maximum seismic capacity of the structure. In the second part of this study, monotonic and reversed-cyclic tests were conducted on the connections between the two subsystems in the proposed hybrid building. The CLT core and light wood-frame structures were connected on the floor level with self-tapping screws (STSs) inserted at 45°, 90°, and mixed angles (45° and 90°). Results show that 45° STSs connections had high stiffness but low energy dissipation, while 90° STS connections had high energy dissipation but low stiffness. Mixed-angle Connections had significantly higher ductility and energy dissipation compared to connections with STSs only inserted at 45° or 90°. The final part of this study investigated the effect of STS connection ductility on the seismic performance of a hybrid building consisting of light wood-frame shear walls and a balloon-type CLT core. The National Building Code of Canada requires the lowest seismic force modification factors (RdRo) of the subsystems be used for the design of a hybrid building if the subsystems are rigidly connected, which may be conservative if a ductile connection is used. Therefore, a numerical study was conducted to determine the possibility of utilizing higher RdRo values for the design of the proposed hybrid structures. Hybrid models were developed where the two subsystems were connected using STS inserted at 45°, 90°, and mixed angles (45° + 90°). Pure light wood-frame structures and pure CLT structures were also analyzed as reference cases. One-, four- and six-storey archetypes were designed with trial RdRo factors. The OpenSees software was used to develop a 2D numerical model for each archetype. The RdRo of the five analyzed cases was evaluated following the Canadian Construction Materials Centre guideline and using the 22 FEMA P695 far-field ground motions. The results show that Rd = 2 and Ro = 1.5 are acceptable for cases of pure CLT structures, and hybrid structures connected using STS inserted at 45° and 90°. The hybrid buildings connected using STS inserted at mixed angles (45° + 90°) can be assigned with Rd = 2.5 and Ro = 1.5. The archetypes designed with Rd = 3 and Ro = 1.7 are deemed satisfactory for pure light wood-frame structures.
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    Advancing risk assessment of climate change and the resiliency of cities
    (2023-07-20) Viseh, Hiva; Bristow, David N.
    Climate change is widely acknowledged to have significant impacts on socio-ecological systems, affecting different regions to varying extents through shocks and stresses related to extreme weather events, sea level rise, and other climate-related changes. This highlights the critical role of adaptation measures in reducing the imposed cost of climate change by increasing urban resilience under a variety of likely climate change-induced scenarios while capitalising on the opportunities presented by a changing climate. The initial step in comprehending the importance of investing in adaptation measures, and subsequently implementing effective strategies in urban areas, is to disseminate information regarding the risks posed by climate change and cultivate awareness and understanding of these risks. While the magnitude of climate change impacts and their resulting socioeconomic consequences still remain uncertain, the increasing complexity and interconnection of diverse social and environmental systems have dramatically impacted our ability to foresee future-imposed threats from climate change. This PhD thesis aims to foster advances in risk perceptions of climate change by progressing risk assessment of potential hazards and changes imposed by climate change on urban areas, as well as by proposing new methods to assess the vulnerability and reliability of complex systems and networks that cities rely on under stresses and shocks, while using all available data and sources, and communicating the complex and multifaceted aspects of climate change in such a way that the data can be used practically in resilience planning and resource allocation. The proposed new methods are: using Euclidean distance in conjunction with the modified Mann-Kendall test to capture both the direction and magnitude of changes in climate data derived from a large number of models; using the Epps-Singleton test to compare climate change in neighbouring cities to see the degree to which it may be possible for adaptation plans to be similar; combining damage functions and probability bound analysis to estimate potential flood damage caused by different climate change-driven flood scenarios at a regional scale by measuring a fraction of the buildings while addressing often-missing uncertainty quantification in damage estimates; and estimating time to failure and repair time of complex systems and networks when dealing with uncertainty in input parameters as well as indeterminant functional dependency using imprecise probability analysis in a probability box approach. In addition, the introduced methods were used to assess the potential variations in diverse climate variables across Canadian cities; to estimate the impact of climate change on flood damage to residential buildings in Metro Vancouver, Canada; to quantify time to failure and repair time of power, water, and wastewater networks, and to calculate the time to failure that an average utility customer of a two-story office building may experience for different types of internal and external functional dependencies.
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    Stress concentration factors for truss-end hollow structural section connections
    (2023-06-14) Ziaeinejad, Ali; Sun, Min
    Design of end connections in a welded hollow structural section (HSS) truss has been a practical problem encountered by structural engineers since current design standards do not include definitive recommendations. For fatigue design, formulae in current design guidelines [for calculation of stress concentration factors (SCFs)] cater to: (i) unreinforced connections, with (ii) sufficient chord continuity beyond the connection on both sides. Existing formulae in CIDECT Design Guide 8 (DG8) for regular connections were shown to be inaccurate for calculation of SCFs for truss-end HSS T- and X-connections. In Chapter 1, a numerical finite element (FE) investigation to determine SCFs for circular hollow section (CHS)-to-CHS X-connections near an open chord end under branch axial loading is presented. Previous large-scale experiments were used to validate FE models, and a parametric study was performed. The parametric study consists of 240 models with variations in chord slenderness (2γ), branch-to-chord diameter ratio (β), branch-to-chord thickness ratio (τ), and chord end distance (e) on one side of the of the connection. Extrapolating existing formulae to predict “end-distance effects” on SCFs at these locations in CHS-to-CHS X-connections, from CIDECT Design Guide 8, were shown to be inaccurate. In Chapter 2, by reinforcing the previous 240 CHS models using a chord-end cap plate and repeating the numerical FE analysis, the SCFs for CHS-to-CHS X-connections near an open chord end was examined. Existing SCF formulae in CIDECT Design Guide 8 were shown to be inaccurate if applied to cap plate-reinforced end connections. Chapter 3 and 4 is a continuation of development of design formulae for truss-end rectangular hollow section (RHS)-to-RHS and CHS-to-CHS connections under in plane bending loading, respectively. Upon validation using the experimental data from previous chapters, a comprehensive parametric study was performed. For this purpose, a total of 448 finite element RHS models including 336 stepped T-connections and 112 matched T-connections (Chapter 3), and 1120 finite element CHS models including 896 stepped T- and X-connections and 224 matched T- and X-connections were created (Chapter 4). Similar to the previous chapters, it was shown that existing formulae in CIDECT Design Guide 8 were unsuitable for the calculation of SCFs for truss-end RHS-to-RHS and CHS-to-CHS moment connections. Finally, SCF correction coefficients (ψ) and parametric formulae to estimate ψ were derived for each chapters.
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    Quantifying the downstream impacts of dams with hydrologic signatures and a large-scale hydrologic model
    (2023-06-02) Liu, Yiran; Troy, Tara
    Rivers are regulated worldwide and are segmented by dams, primarily built in the last century. The impact of dams on flow immediately downstream has been studied for decades. However, the downstream propagation of the hydrologic impacts in a river network still needs to be better quantified, particularly in humid regions. This study aims to test a method of investigating the impacts of large reservoirs by using different hydraulic signatures, determining how the signatures propagate downstream of the dams, and exploring the potential to utilize a hydrologic model to determine dam impacts. By solely analyzing streamflow observations in the Delaware River Basin, hydrologic signatures can detect the dams’ impacts immediately downstream of the New York City reservoirs and are able to show the length scale at which hydrologic signatures return to unimpacted values within the Delaware River basin. Results show that the streamflow downstream was influenced by the large reservoirs but with a propagation distance of approximately 35 kilometers, after which the signatures are likely to be consistent with gauges upstream of the reservoirs. Unlike the western U.S., the streamflow below large dams shows the potential to recover via streamflow contributions from the tributaries in a humid watershed, resulting in a less vulnerable river regime; however, the flashier streamflow and the change in timing locally downstream of the dams may result in ecological degradation. This method developed for the Delaware basin to compare hydrologic signatures in time and space is transferable to other river basins. Another potential approach is to use a hydrologic model to simulate unregulated streamflow which can serve as a proxy for naturalized hydrologic signatures. The Variable Infiltration Capacity (VIC) model was selected to explore the possibility of expanding the observation-based method. Due to the poor streamflow performance in an initial simulation, especially for the baseflow, the second chapter of this thesis focuses on better understanding the VIC baseflow generation and its sensitivity to model parameters. To do this, seven calibration parameters with three different values each are selected for a sensitivity analysis. The results suggest that the infiltration parameter (infil), the exponent in the equation for hydraulic conductivity (exp), and the parameter that specifies the maximum baseflow (dsmax) play important roles in determining the baseflow simulation and also influence the baseflow sensitivity of other parameters. This emphasizes the importance of precipitation partitioning and the vertical drainage process in baseflow simulation, in addition to the actual baseflow curve for the bottom soil layer. Based on the results of the sensitivity analysis, VIC is expected to be able to correctly simulate baseflow and total streamflow after calibration but this modeling exercise revealed significant challenges and limitations. Typical calibration methods that rely on monthly streamflow need to be improved, while calibrating to daily streamflow is important because of the need to capture the hydrograph characteristics, like the correct recession curve. Spatial heterogeneity needs to be considered, and the calibration parameters may not be transferable between gauges, even at a relatively small distance. If VIC can represent the naturalized streamflow regime, there is a potential to do a similar tracing downstream as in Chapter 2. Both methods could then be applied to other basins.
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    Flexibility assessment of Canada’s electricity system for deep decarbonization
    (2023-05-25) Saffari, Mohammadali; McPherson, Madeleine
    In accordance with the Paris Climate Agreement, Canada has committed to reaching net-zero greenhouse gas (GHG) emissions by 2050, necessitating decarbonization across various sectors, including the electrical grid. The widespread deployment of variable renewable energy (VRE) sources holds the potential for a carbon-free electrical grid. However, the variable nature of VRE can result in technical challenges such as network frequency fluctuations, requiring a highly flexible power network to address these issues. Both the demand side and generation side can contribute to network flexibility. Generation-side flexibility can be provided by high ramping generators, such as hydro units, while demand response programs can incentivize customers to adjust their consumption patterns, offering demand-side flexibility. This PhD dissertation seeks to investigate the decarbonization of Canada's electricity system through VRE integration, with a focus on flexibility assessment on both the generation and demand sides. The investigation of VRE integration in this study centers on employing the operation (optimal dispatch) model. The present study undertakes an examination of Canada's existing electrical system with a view to exploring its capability for the integration of VRE. The study commences by evaluating the generation-side flexibility and transmission network adequacy of the system. Thereafter, it examines two strategies aimed at enhancing the integration of VRE. The first strategy considers integrated operation of neighboring networks to leverage flexibility and enhance VRE integration in less flexible networks. The second strategy assesses the impact of demand-side flexibility in enhancing VRE integration. The findings demonstrate that Canada's hydro-dominated electrical network possesses significant potential for integrating VRE, which leads to a significant reduction in GHG emissions. Nonetheless, the current potential falls short of achieving net zero emissions, implying the need for further actions to reach this goal. The integration of neighboring electrical networks through integrated operation can enhance flexibility and VRE integration in networks that are less flexible. However, high flexible networks in Canada, dominated by hydropower, may have their flexibility provision capacity impacted by climate change. This implies that a range of flexibility resources must be taken into consideration to ensure secure and reliable VRE integration. Demand side flexibility can aid in facilitating VRE integration, however, its efficacy is contingent on consumer behavior and preferences, as well as incentives offered by the system operator. Additionally, the findings indicate that the transmission network holds a crucial role in achieving maximum flexibility on both the generation and demand sides. An inadequate transmission capacity can serve as a hindrance to achieving maximum VRE integration.
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    Design of Fillet and PJP Welds in CHS-to-CHS Moment T-Connections: Finite Element Investigation
    (2023-04-26) Zhang, Chengcheng; Sun, Min
    This paper presents a study to evaluate the effective geometric property approach in AISC 360-22 for design of welds in circular hollow section (CHS)-to-CHS moment T-connections under in-plane bending. Experimental data from previous full-sized connection tests is used to verify a finite element (FE) modelling approach for weld-critical connections. A subsequent FE parametric study, including 137 fillet and partial-joint-penetration groove welded CHS-to-CHS connection models, is performed to cover wide ranges of nondimensional design parameters: branch-to-chord diameter ratio (0.4 to 1.0), branch-to-chord thickness ratio (0.2 to 1.0), and chord slenderness ratio (10 to 50). New formulae in recent research for calculation of the weld effective elastic section modulus for in-plane bending are evaluated, and modifications are proposed. The proposed modifications provide more accurate predictions of weld strength yet still achieve sufficient safety margins.
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    Holistic Post-Occupancy Evaluation of The Harmless Home
    (2023-04-05) Costa Sousa, Rafael Wildson; Froese, Thomas M.
    Post-occupancy evaluation (POE) is a method that can provide feedback throughout a building's lifecycle from the initial concept to the occupation. From this feedback, it is possible to help stakeholders, designers, and policymakers with recommendations for future projects from the lessons learned in the previously evaluated building. Having that said, the research objective is to assess the performance of the Harmless Home and Just BioFiber holistically in order to help stakeholders, designers, and policymakers to have more options to achieve the carbon net-zero building requirement. A POE of the Harmless Home was conducted using the International Initiative for a Sustainable Built Environment (iiSBE) protocol to investigate and analyze the results. Four critical key performance indicators (KPIs) were analyzed in this paper: energy and emissions, water, indoor environmental quality (IEQ), and cost. Several lessons were taken for this, but the most significant one is for the energy and emissions, showing that the exterior wall had a higher R-value than predicted in the building energy modelling (BEM), resulting in less energy consumption. Furthermore, the solar panels were able to produce more energy than required in the house, enabling them to return energy to the grid and consequently saving CO2. More specifically, about the JBF, two evaluations were done regarding its performance: (1) hygrothermal performance analysis and (2) life cycle assessment. Hygrothermal performance analysis of the modified hempcrete used in the Harmless Home from Just BioFiber (JBF) in different Canadian climate zones and with different geographic orientations and exterior finishing to analyze where it would be possible to use the block without any additional vapour retarder. In order to analyze the hygrothermal performance, two main criteria were considered, the moisture content over time in different layers of the wall assembly and the improved model to predict mould growth revised and adopted by ASHRAE standard 160-2016. From the Canadian zones analyzed, climate zone 6 with a wind-driven oriented accumulated moisture over time, and climate zone 5 (both standard and wind-driven oriented) and 6 (non-wind-driven oriented) should have additional attention like the mould growth index (MGI). And last but not least, the environmental impact assessment of the Harmless Home and JBF LCA was conducted to analyze the embodied and operational carbon emissions. Two different construction methods were compared in the whole building life cycle assessment: (1) modified hempcrete block (JBF) for the exterior walls and insulated concrete forms (ICF) for the foundation compared to (2) the traditional construction method used in Canada with wood-frame for the exterior walls and reinforced concrete for the foundation in a whole-building LCA using One Click LCA as an LCA platform. Regarding the embodied carbon emissions, case (1) released 14% less greenhouse gas emissions than case (2), also having the ability to sequester 13 tons of CO2e. Regarding the operational carbon, both cases could save 11 tons of CO2e due to solar panels' energy production higher than the necessary usage of the house in 60 years. Thus, the main conclusion is that building material selection should be considered concerning the urgent need to mitigate global climate change impacts. CO2e. From the overall results across all the performances, the Harmless Home and JBF performed well regarding the POE, hygrothermal performance and LCA, which, based on the results, can contribute to minimizing environmental impacts and mitigating climate change.
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    Multi-infrastructure restoration modeling to support regional planning for recovery following earthquakes
    (2023-03-20) Deelstra, Andrew; Bristow, David
    The complexity and interconnected nature of critical infrastructure systems across metropolitan regions presents a unique challenge for communities to understand how they may respond and recover in the face of a major disruption. Disaster recovery modeling facilitates coordination and planning among stakeholders, but detailed system models are often complex and require significant technical skill to construct and interpret. The first part of this work presents the development and assessment of a simplified seismic recovery model for water, wastewater, and power systems in the Metro Vancouver region of British Columbia, Canada. The model considers important geospatial and interdependent characteristics of multi-infrastructure systems without requiring access to complete operational models. The model is expanded in the second part of this work to consider the effectiveness of disaster risk reduction measures on infrastructure service recovery to the population after the earthquake. Finally, a detailed hydraulic water system analysis is compared to the simplified modeling approach for a seismic hazard scenario to consider how results from each compare given various restoration strategies. Results from the three sections of this work demonstrate the utility of a simplified multi-infrastructure modeling approach for assessing recovery at a regional scale, the potential benefits of investing in disaster risk reduction measures to improve recovery outcomes for residents, and aspects of modeling approaches that provide an understanding of their use and benefits for disaster management purposes.
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