Monitoring of Dynamic Bridge Behaviour Using Digital Image Correlation

Bridges are a critical part of North America’s transportation network that need to be assessed frequently to inform bridge management decision making. Visual inspections are usually implemented for this purpose, during which inspectors must observe and report any excess displacements or vibrations. Unfortunately, these visual inspections are subjective and often highly variable and so a monitoring technology that can provide quantitative measurements to supplement inspections is needed. Digital Image Correlation (DIC) is a novel monitoring technology that uses digital images to measure displacement fields without any contact with the bridge. In this research, DIC and accelerometers were used to investigate the dynamic response of a railway bridge reported to experience large lateral displacements. Displacements were estimated using accelerometer measurements and were compared to DIC measurements. It was shown that accelerometers can provide reasonable estimates of displacement for zero-mean lateral displacements. By comparing measurements in the girder and in the piers, it was shown that for the bridge monitored, the large lateral displacements originated in the steel casting bearings positioned above the piers, and not in the piers themselves. The use of DIC for evaluating the effectiveness of rehabilitation of the LaSalle Causeway lift bridge in Kingston, Ontario was also investigated. Vertical displacements were measured at midspan and at the lifting end of the bridge during a static test and under dynamic live loading. The bridge displacements were well within the operating limits, however a gap at the lifting end of the bridge was identified. Rehabilitation of the bridge was conducted and by comparing measurements before and after rehabilitation, it was shown that the gap was successfully closed. Finally, DIC was used to monitor the midspan vertical and lateral displacements in a monitoring campaign of five steel rail bridges. DIC was also used to evaluate the effectiveness of structural rehabilitation of the lateral bracing of a bridge. Simple finite element models are developed using DIC measurements of displacement. Several lessons learned throughout this monitoring campaign are discussed in the hope of aiding future researchers.

DIGITAL HISTORY: DESIGNING VIRTUAL ENVIRONMENTS THAT SUPPORT CRITICAL THINKING AND IDEA EXCHANGE, MOTIVATE AND ENGAGE USERS

In my thesis I argue for the use of system designs that: a) open access to a variety of users and allow for collaboration and idea exchange, while at the same time, b) are designed to motivate and engage users. To exemplify my proposed systems design, I created an interactive and open digital history project focused on Romanian culture and identity during Communism, from 1947, when the Communist Party took power by forcing the King to abdicate, until the revolution in 1989, which marked the end of Communism in Romania (Gilberg, 1990, Boia, 2014). In my project, I present the possibility to recreate Habermas’ notion of public sphere and “the unforced force of the better argument” (Habermas, 1989) and Dewey’s (2004) understanding of democracy as a mode of associated living imbued of the spirit of inquiry within contemporary digital history projects. Second, I outline system designs that motivate and engage users, by satisfying the basic psychological needs outlined in Ryan and Deci’s (2000) self-determination theory: autonomy, competence, and relatedness. Two more concepts are included to complete the proposed digital history project design: presence (Ryan, Rigby, & Przybylski, 2006) and learner hero (Rigby & Przybylski, 2009).

Digital geometric-sequence control technique for bidirectional dual active bridge DC-DC converters used in future electric vehicles

Bidirectional DC-DC converters are widely used in different applications such as energy storage systems, Electric Vehicles (EVs), UPS, etc. In particular, future EVs require bidirectional power flow in order to integrate energy storage units into smart grids. These bidirectional power converters provide Grid to Vehicle (V2G)/ Vehicle to Grid (G2V) power flow capability for future EVs. Generally, there are two control loops used for bidirectional DC-DC converters: The inner current loop and The outer loop. The control of DAB converters used in EVs are proved to be challenging due to the wide range of operating conditions and non-linear behavior of the converter. In this thesis, the precise mathematical model of the converter is derived and non-linear control schemes are proposed for the control system of bidirectional DC-DC converters based on the derived model. The proposed inner current control technique is developed based on a novel Geometric-Sequence Control (GSC) approach. The proposed control technique offers significantly improved performance as compared to one for conventional control approaches. The proposed technique utilizes a simple control algorithm which saves on the computational resources. Therefore, it has higher reliability, which is essential in this application. Although, the proposed control technique is based on the mathematical model of the converter, its robustness against parameter uncertainties is proven. Three different control modes for charging the traction batteries in EVs are investigated in this thesis: the voltage mode control, the current mode control, and the power mode control. The outer loop control is determined by each of the three control modes. The structure of the outer control loop provides the current reference for the inner current loop. Comprehensive computer simulations have been conducted in order to evaluate the performance of the proposed control methods. In addition, the proposed control have been verified on a 3.3 kW experimental prototype. Simulation and experimental results show the superior performance of the proposed control techniques over the conventional ones.

Disability in the Digital Age: Reconfiguring Access, Inclusion and Equality

There is an abundance of research that examines disability and technology in the context of computers and the Internet, however few have examined disability and mobile devices. Also largely absent from existing literature are the voices of disabled people themselves. This dissertation draws upon science and technology studies (STS) and disability studies to address these gaps by conducting in-depth qualitative research that examines disabled people’s experiences using smartphones and tablets. At its core, this dissertation aims to provide insight on the following: 1) an understanding of how disability is perceived in the digital age and the subjective meanings of access, inclusion and equality; 2) the ways in which mobile devices impact the lived experience of disability; and 3) how perspectives in disability studies and STS can be applied to understand the relationship between the body, disability and technology. The empirical contribution of this research draws from participant diaries and interviews with disabled people, as well as from open-ended questionnaires completed by mobile app developers. The concept of ‘subjectivities of disability’ is introduced to refer to the uniquely personal and individual experience of disability. Findings reveal that mobile device use amongst disabled people redefines their subjectivities of disability through socio-technical interactions whereby disabled people use their devices in ways that are integrated into their everyday lives and positively shapes how they view themselves in relation to their experience of disability. The responses from app developers reveal that there is a place for disability in the mobile market and that disabled people play a key role in making apps accessible. The data suggests that mobile devices facilitate access, inclusion and equality by integrating the body in ways that recognize and accommodate diversity. The results furthermore make it clear that the interaction between disabled people and mobile devices takes on an embodied and social characteristic. This research concludes that both on an individual level and collectively, disabled people are engaging with digital artifacts in ways that promote agency and independence as well as reshaping how disability is experienced and perceived in the digital age.

Governing Big Data: The Political Economy of Power, Knowledge and Consumer Finance in the Digital Age

This dissertation offers a critical international political economy (IPE) analysis of the ways in which consumer information has been governed throughout the formal history of consumer finance (1840 – present). Drawing primarily on the United States, this project problematizes the notion of consumer financial big data as a ‘new era’ by tracing its roots historically from late nineteenth century through to the present. Using a qualitative case study approach, this project applies a unique theoretical framework to three instances of governance in consumer credit big data. Throughout, the historically specific means used to govern consumer credit data are rooted in dominant ideas, institutions and material factors.