Mental health struggles and suicide rates in athletic populations have been on the rise for the past two decades, with an even bigger increase since the pandemic. Disorders such as stress, depression, and anxiety have been the main causes for these struggles and fatalities. The growing rates of mental health disorders and suicide within this population indicate that athletes do not have the adequate resources to restore and improve their mental health. In some instances of presenting their troubles to coaches, staff, or teammates, their only advice is to seek help with on-campus resources or resources at home. Although this can be sound advice in some cases, this can also create the sense that there is no escape from what may be the cause of these mental obstacles. The purpose of this thesis is to create a mental health retreat for collegiate, professional, olympic, and retired athletes. Tucked away at the edge of Rock Creek Park in Washington, D.C., in between existing amenities such as the Carter Barron Amphitheatre and the William Fitzgerald Tennis Center, the retreat allows for the continual use of existing amenities along with other resources and practices provided on-site. This retreat aims to provide spaces and resources at a location that teams or individuals can visit to allow for healing and education about these mental health disorders. This serene space in the middle of a chaotic big city will provide space for resting, performing, healing, and overall restoring which begins to break the barriers between what can be overcome in the feelings that may seem indomitable. / Master of Architecture / Mental health struggles and rising suicide rates among athletes have become increasingly concerning over the past two decades, with a significant spike since the pandemic. Stress, depression, and anxiety are the primary issues affecting this population, and current resources appear inadequate to address their needs. Often, athletes are advised to seek help from on-campus or home resources, which may not always be effective and can sometimes exacerbate feelings of entrapment. This thesis proposes the creation of a mental health retreat for collegiate, professional, Olympic, and retired athletes. Located at the edge of Rock Creek Park in Washington, D.C., near amenities like the Carter Barron Amphitheatre and the William Fitzgerald Tennis Center, this retreat offers a peaceful environment for healing and education. By utilizing existing amenities and providing additional on-site resources and practices, the retreat aims to support athletes in their mental health journeys. This serene space in the heart of a bustling city will offer opportunities for rest, performance, healing, and overall restoration, helping athletes overcome mental health challenges.

This qualitative research study was designed to follow-up with ten participants in a relapse prevention program at an inpatient psychiatric unit with a diagnosis of major depression for the purpose of determining their experiences post-discharge in practicing relapse prevention and in pursuing and maintaining wellness in their mental health. It relied upon narrative theory, theories of self-efficacy, and theories of depression to guide the research process as well as the field of knowledge about rehospitalization, relapse prevention, depression, and self-efficacy. Participants described depression associated with loss, feeling helpless, powerless, overwhelmed and suicidal. They increased in their confidence of depression management as their depression got better and they actively managed it. During the interviews participants expressed themes of connection, with participants feeling disconnected from themselves and others, wanting to be listened to, but feeling unheard or hiding their own voice, a loss of self with healing occurring through use of self, learning cognitively and experientially to manage their depression using specific self-efficacy skills and identifying the things that interfered with depression management. A relational theory of depression management, based on attachment theory is proposed and several suggestions for research and treatment are made. / Ph. D.

The strength and behavior of composite slabs are governed by the shear interaction between the concrete and the steel deck. The interaction property depends on several factors and it is not possible to express the relationship from a purely analytical basis. As such, analysis and design methods available today use the interaction property derived from full scale performance tests. In numerical modeling, the interaction property is obtained from a variety of elemental push off tests which, for the most part, do not represent actual slab bending. This research comprises experimental, analytical and numerical investigations of composite slabs. The central objective of the experimental work is to develop a new small scale test method for evaluating the performance and behavior of composite slabs and also for determining the shear interaction property for use in numerical analysis. The characteristics of the new test specimen are simple, easy and economical to conduct, as well as comparable in performance and behavior with the more common full slab test. The analytical study was conducted to determine whether data from small scale tests can be used in the present analytical methods to predict the strength of the actual slabs, to use the same test data for input in the numerical analysis, and to improve the present Partial Shear Connection (PSC) design procedure. A model that relates the shear bond stress to slab slenderness, which can be used to estimate the shear interaction property for slabs with any slenderness, was developed. Finally, a finite element study was conducted to develop a simple modeling method that is suitable for analyzing composite slabs with variable slenderness. Parametric analyses to determine the effect of slenderness on the performance and behavior of composite slabs, and on the accuracy of the present design methods were also conducted. The results of this investigation demonstrate that the small scale test is feasible as a replacement for the full scale test. Data from the small scale test can be used not only in the analytical methods but also in the numerical analysis, thus eliminating the need for separate push off type tests. / Ph. D.

The electric power system is undergoing a paradigm change on how electric energy is generated, transmitted, and delivered. Power electronics systems which can provide medium-voltage (MV) to high-voltage (HV) output (>13.8 kV ac, > 20 kV dc) with much faster dynamic response (> 10 kHz bandwidth) or high switching-frequency will enable new electronic energy network architectures, like MVDC power delivery, underground solid-state power substation (SSPS), and high-density power electronics building block (PEBB); help drive the levelized cost of electricity (LCOE) of renewable energy on par with conventional power generation; deliver precise and clean power to loads like high-speed electric motors; push the future power system toward 100% renewable energy and energy storage supplied. In the MV to HV area, the power conversion solution is dominated by silicon devices, like SCR, IGCT, and IGBT, which are slow in nature, posing significant switching losses and bulky auxiliary components like turn-on snubbers. Devices in series are required to reach higher voltage. High-frequency HV converter in two-level or three-level bridges running 20 kHz or higher in many emerging applications, like MVDC networks with high-frequency transformers and energy storage integration is hard to be built by silicon solutions. The emerging HV wide-bandgap (WBG) power semiconductors, e.g., 10 kV SiC MOSFETs offer higher blocking capability, faster and more efficient switching performances. This makes the high-frequency power conversion technology feasible for the MV area. To build a MV high-frequency power converter with high-power density, 10 kV SiC MOSFETs in series are required to reach >10 kV operation dc voltage as the single device rating is still limited by the semiconductor process and packaging capability. However, the knowledge of dynamic voltage sharing of high-speed HV SiC devices under high dv/dt rate and effective balancing methods are not fully explored. Both the voltage imbalance and the robust device voltage balancing control are not studied clearly in the existing literature. This dissertation evaluates the voltage imbalance of series-connected 10 kV SiC MOSFETs thoroughly. The parasitic capacitors connected with device terminals are found to be a unique factor for the voltage imbalance of series-connected SiC MOSFETs, which have a significant impact on the dv/dt of different devices based on the detailed analysis. The unbalanced dv/dt and the gate signal mismatch together result in the voltage imbalance of series-connected SiC MOSFETs and a set of new voltage balancing control methods are proposed. Passive capacitor compensation and closed-loop short pulse gate signal control are proposed to solve the voltage imbalance caused by the unbalanced dv/dt. Closed-loop gate delay time control is proposed to solve the voltage imbalance caused by the gate signal mismatch. Two gate driver prototypes are designed and verified for the proposed voltage balancing control methods. As the number of devices increases, the voltage balancing methods under the device-level will be complex and risky to coordinate. Therefore, the converter-level device voltage balancing methods are desired when over three devices are in stack. Therefore, this dissertation proposes to use the 3-level (3L) neutral-point-clamped (NPC) converter structure as a converter-level approach to simplify the voltage balancing control of series-connected SiC MOSFETs. A new modulation strategy is proposed to control the loss of clamping diodes, so compact MV SiC Schottky diodes can be selected to reduce the impact of extra components on the power density. Compared to the phase-leg with direct series-connected SiC MOSFETs, the phase-leg designed with the converter-level approach achieves similar power density, easier voltage balancing control, and better efficiency, which is attractive for both two and four devices in series connection. Finally, this dissertation studies the impact of series-connected 10 kV SiC MOSFETs on MV phase-leg volume reduction with the example of multi-level flying capacitor (FC) converters. The relation between the capacitances of FCs and the device voltage is studied and a new design procedure for FCs is developed to achieve minimum FC energy and regulate the maximum device voltage. With the design procedure, the total FC volumes of a 22 kV 5-level FC converter and a 22 kV 3-level FC converter with series-connected 10 kV SiC MOSFETs are calculated and compared. Series-connected 10 kV SiC MOSFETs are found to help significantly reduce the total FC volume (> 85 %). In summary, this dissertation demonstrates that the direct series connection of 10 kV SiC MOSFETs is a reliable solution for the MV converter design, and the converter-level approach is a better voltage balancing control method. This dissertation also presents a quantitative analysis of the volume reduction enabled by the series-connected 10 kV SiC MOSFETs in MV converter phase-leg design. / Doctor of Philosophy / Emerging industrial applications require medium voltage (MV) power converters. For existing MV converter solutions with Si IGBT, complex system structures are usually required, which affects the efficiency, power density, and cost of the system. For the design of MV converter, the recent 10 kV SiC MOSFET has the promising potential to improve efficiency and power density by adopting a simpler topology and fewer conversion stages. New design challenges also emerge with the new 10 kV SiC MOSFETs and one of them is the device voltage control during the operation. This dissertation mainly focuses on the voltage balancing control of series-connected 10 SiC MOSFETs, which is an attractive solution to build the MV converter phase-leg in a simple structure. Several voltage balance control methods are proposed and compared in this dissertation, which helps justify that the series-connected SiC MOSFET is a reliable approach for the MV converter design. In addition, this dissertation also analyzes the volume reduction enabled by the series-connected SiC MOSFETs with the example of a multi-level flying capacitor converter in dc-ac applications.

An innovative approach to possible construction or rehabilitation of bridge decks can be found in a bridge construction system called the Sandwich Plate System (SPS). The technology developed and patented by Intelligent Engineering Canada Limited in conjunction with an industry partner, Elastogran GmbH, a member of BASF, may be an effective alternative to traditional bridge rehabilitation techniques. Although the system's behavior has been studied the connection of the SPS deck to the supporting girders has not been investigated. Two types of connection are presented in this research. The use of a bent plate welded to the SPS deck and subsequently bolted to the supporting girder utilizing slip-critical connections has been utilized in the construction of a SPS bridge. A proposed SPS bridge system utilizes the top flange of the supporting girder welded directly to the SPS deck as the deck-to-girder connection. The fatigue performance of a deck-to-girder connection utilizing a bent plate welded to the deck and bolted to the supporting girder using slip-critical connections was tested in the Virginia Tech Materials and Structures Laboratory. The testing concluded that the fatigue performance of the welded and bolted bent plate connection was limited by the weld details and no slip occurred in the slip-critical connections. Finite element modeling of the two types of deck-to-girder connections was also used to determine influence of the connections on the local and global behavior of a SPS bridge system. A comparison of the different connection details showed that the connection utilizing the flange welded directly to the SPS deck significantly reduces the stresses at location of the welds in the connections, but the connection type has a limited influence on the global behavior of a SPS bridge. / Master of Science

The phenomenon of news avoidance receives increasing scholarly attention as small but growing parts of society decrease or terminate their news intake. This development is particularly visible among younger generations, correlating with an increasing wish to disconnect digitally. The severity of news avoidance for society depends on the chosen democratic model. Following Habermas’ understanding of deliberative democracy theory, citizens are expected to be informed and willing to connect to the public. However, there are considerations for a change in citizenship ideals that reflect the implications of the digitalized world in which news consumption is situated. Consequently, there is a shift away from the normative expectation of always being informed, and even alternative ways of public connection have emerged. To explore the tension between news avoidance, the normative expectations of public connection, and the call for a more realistic view of today’s citizenship, this study explores news avoidance among young Swedish citizens. In ten in-depth interviews with young news avoiders, motivations for their low levels of news consumption were explored, leading to three categories: mental health, relevancy, and structural factors. Repeatedly mentioned were the personal considerations that news consumption decreased mental well-being and that free time was preferably used for personal interests. Additionally, the wish to disconnect from digital devices either directly or indirectly influenced news consumption. Moreover, understandings of citizenship were examined, showing various views ranging from cultural belonging to obligations. Regarding civic duties, the findings were ambivalent, showing both an understanding and a questioning of news consumption as a duty for citizens. Alternative ways of public connection, such as TV shows or social media consumption, seemed insufficient. Concluding, from the standpoint of deliberative democracy, the findings on news avoidance and participants’ understanding of citizenship pose a challenge for democratic societies that hampers public connection.

Concrete technology has been in changeful evolution since the Roman Empire time. It is remarkable that the technological progress became of higher magnitude from the second part of the XX Century. Advances in the development of new cements, the appearance of the fibers as a reinforcement for structural applications, and specially the grand progress in the field of the water reducing admixtures enabled the emergence of several types of special concretes. One of the lasts is the Ultra High Performance Fiber Reinforced Concrete (UHPFRC), which incorporates advances of the Self-Compacting Concrete (SCC), Fiber-Reinforced Concrete (FRC) and Ultra High Strength Concrete (UHSC) technology. This exclusive material requires a detailed analysis of the components compatibility and a high control of the materials and processes. Mainly patented products have been used for the few structural elements carried out so far today, but the costs makes doubtful the development of many other potential applications. In accordance with the previously explained, a simplification of the UHPFRC components and processes is needed. This becomes the first main goal of this Ph.D. thesis, which emphasizes in the use of local available components and simpler mixing processes. Moreover, the singular properties of this material, between ordinary concrete and steel, allow not only the realization of slenderer structures, but also the viability of new concepts unthinkable with ordinary concrete. In this field is focused the second part of the Ph.D. thesis, which develops a bolted connection system between UHPFRC elements. This research summarizes, first of all, the subfamilies belonging to the HPC-UHPC materials. Afterwards, it is provided a detailed comparison between the dosage and properties of more than a hundred of mixtures proposed by several authors in the last ten years of technology. This becomes a useful tool to recognize correlations between dosages and properties and validate or no preconceived ideas about this material. Based on this state of art analysis was performed the later development of mixtures, on Chapter 4, which analized the effect of use of simpler components and processes on the UHPFRC. The main idea was use local components available in the Spanish market, identifying the combinations that provide the best rheological and mechanical properties. Steam curing use was avoided since a process simplification is intended. Diferent dosages were developed to be adapted to various levels of performance, and always trying to be as economical as possible. The concretes designed were selfcompacting and mainly combined two fiber types (hybrid), as the flexural performance was of greater relevance. The compressive strength obtained varied in the range between 100 and 170 MPa (cube L=100 mm), and the flexural strength between 15 and 45 MPa (prism 100 x 100 x 500 mm). Some of the components introduced are very rarely used in UHPFRC, as limestone coarse aggregate or FC3R, a white active residue from the petrol industry. As a result of the research, some simple and practical tips are provided for designers of UHPFRC dosage. At the end of this chapter, five dosages are characterized as examples of useful concretes for different requirement applications. In a second part, the idea of a bolted joint connection between UHPFRC elements was proposed. The connection system would be especially useful for struts and ties elements, as truss structures. The possible UHPFRC failure modes were introduced and two different types of tests were designed and performed to evaluate the joint capacity. The geometry of the UHPFRC elements was modified in order to correlate it with the failure mode and maximum load reached. Also a linear finite element analysis was performed to analyze the UHPFRC elements connection. This supported the results of the experimental tests to deduce formulations that predict the maximum load for each failure mode. Finally, a real size truss structure was assembled with bolted joints and tested to verify the good structural behavior of these connections. To conclude, some applications designed and developed at the Universitat Politècnica de València with the methods and knowledge acquired on UHPFRC are abstracted. In many of them the material was mixed and poured in a traditional precast concrete company, providing adequate rheological and mechanical results. This showed the viability of simpler UHPFRC technology enabling some of the first applications in Spain with this material. / Camacho Torregrosa, EE. (2013). Dosage optimization and bolted connections for UHPFRC ties [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34790

no abstract provided by author / Master of Architecture

The adjacent box beam bridges (ABBB) are considered as an ideal solution for short to medium span bridges and for routes with low to medium traffic volumes. The ABBB system has been utilized and is popular in several states in the United States. However, this bridge system has long term durability issues caused by shear key failure and reflective cracking in the topping. The means and methods to alleviate the problems in connections between members of the ABBB were researched and the development of new connection details was pursued. Diagnostic tests to study the in-service behavior of ABBBs was performed. Two bridges with varying magnitude of joint deterioration were investigated. Both bridges were instrumented extensively and were subjected to known loads in the form of tandem trucks. The response of these bridges was studied and conclusions were made about the state of the bridges and the behavior after shear key failure. A finite element (FE) model of one of the tested bridges was developed to study the response of an ABBB with sound joints. The results of the finite element analysis (FEA) were compared with the results of the bridge diagnostic test. Conclusions about the FE model were made on the basis of this comparison. Another FE model, referred as the full scale bridge (FSB) was developed. The FSB model was used to simulate the behavior of an ABBB with the proposed connection details. This FSB model was subjected to design truck loads and the response was studied. The behavior of FSB model was replicated through a three beam sub-assembly that was supported on elastic supports. The stiffness of the elastic supports was calibrated such that the state of stress in the joints and the relative displacements between adjacent box beams in the sub-assemblage matched those in the FSB. The three beam sub-assembly was constructed with the proposed connection details. Two new connection details were proposed in this research. A Kevlar and epoxy connection and a spliced connection with fiber reinforced self-consolidating concrete are proposed. A total of six specimens, with different connection details, were constructed and tested for strength and durability in the laboratory. The behavior of the proposed connections and the connection materials were studied in detail. Additional FEA was performed to study the effect of shrinkage and temperature on the proposed connection details. / Ph. D.

No / In steel¿concrete composite beams, the longitudinal shear force is transferred across the steel flange/concrete slab interface by the mechanical action of the shear connectors. The ability of the shear connectors to transfer these longitudinal shear forces depends on their strength, and also on the resistance of the concrete slab against longitudinal cracking induced by the high concentration of shear force. Most of the research in composite construction has concentrated on the more traditional reinforced concrete and metal deck construction, and little information is given on shear capacity of the headed studs in precast hollowcore slabs. In this paper, a standard push test procedure for use with composite beams with precast hollowcore slabs is proposed. Seven exploratory push tests were carried out on headed studs in solid RC slabs to validate the testing procedures, and the results showed that the new test is compatible with the results specified in the codes of practice for solid RC slabs. Once a standard procedure is established, 72 full-scale push tests on headed studs in hollowcore slabs were performed to determine the capacities of the headed stud connectors in precast hollowcore slabs and the results of the experimental study are analysed and findings on the effect of all the parameters on connectors¿ strength and ductility are presented. Newly proposed design equations for calculating the shear connectors¿ capacity for this form of composite construction are also be given.