Recently, numerous flexible structures have been employed in various fields of industry. Loading conditions sustained by these flexible structures are often not described well enough for engineering analyses even though these conditions are important. Here, a flexible tent with an interior Collective Protection System, which is subjected to an explosion, is analyzed. The tent protects personnel from biological and chemical agents with a pressurized liner inside the tent as an environmental barrier. Field tests showed unexpected damage to the liner, and most of the damage occurred on tent's leeward side. To solve this problem, various tests and analyses have been performed, involving material characteristics of the liner, canvas, and zip seals, modeling of the blast loading over the tent and inside the tent, and structural response of the tent to the blast loading as collaborative research works with others. It was found that the blast loading and the structural response can not be analyzed separately due to the interaction between the flexible structure and the dynamic pressure loading. In this dissertation, the dynamic loadings imposed on both the interior and the exterior sides of the tent structure due to the airblasts and the resulting dynamic responses were studied. First, the blast loadings were obtained by a newly proposed theoretical method of analytical/empirical models which was developed into a FORTRAN program. Then, a numerical method of an iterative Fluid-Structure Interaction using Computational Fluid Dynamics and Computational Structural Dynamics was employed to simulate the blast wave propagation inside and outside the flexible structure and to calculate the dynamic loads on it. All the results were compared with the field test data conducted by the Air Force Research Laboratory. The experimental pressure data were gathered from pressure gauges attached to the tent surfaces at different locations. The comparison showed that the proposed methods can be a good design tool to analyze the loading conditions for rigid or flexible structures under explosive loads. In particular, the causes of the failure of the liner on the leeward were explained. Also, the results showed that the effect of fluid-structure interaction should be considered in the pressure load calculation on the structure where the structural deflection rate can influence the solution of the flow field surrounding the structure. / Ph. D.

The response of submerged structures subject to loading by underwater blast waves is governed by complex interactions between the moving or deforming structure and the surrounding fluid and these phenomena need to be thoroughly understood in order to design structural components against underwater blast. This thesis has addressed the response of simple structural systems to blast loading in shallow or deep water environment. Analytical models have been developed to examine the one-dimensional response of both water-backed and air-backed submerged rigid plates, supported by linear springs and loaded by underwater shock waves. Cavitation phenomena as well as the effect of initial static fluid pressure are explicitly included in the models and their predictions were found in excellent agreement with detailed FE simulations. Then, a novel experimental apparatus has been developed, to reproduce controlled blast loading in initially pressurised liquids. It consists of a transparent water shock tube and allows observing the structural response as well as the propagation of cavitation fronts initiated by fluid-structure interaction in a blast event. This experimental technique was then employed to explore the one-dimensional response of monolithic plates, sandwich panels and double-walled structures subject to loading by underwater shock waves. The performed experiments provide great visual insight into the cavitation process and the experimental measurements were found to be in good agreement with analytical predictions and dynamic FE results. Finally, underwater blast loading of circular elastic plates has been investigated by theoretically modelling the main phenomena of dynamic plate deformation and fluid-structure interaction. In addition, underwater shock experiments have been performed on circular composite plates and the obtained measurements were found in good correlation with the corresponding analytical predictions. The validated analytical models were then used to determine the optimal designs of circular elastic plates which maximise the resistance to underwater blast.

With the increased frequency of accidental and deliberate explosions, the response of civil infrastructure systems to blast loading has become a research topic of great interest. However, with the high cost and complex safety and logistical issues associated with live explosives testing, North American blast resistant construction standards (e.g. ASCE 59-11 & CSA S850-12) recommend the use of shock tubes to simulate blast loads and evaluate relevant structural response. This study aims first at developing a 2D axisymmetric shock tube model, implemented in ANSYS Fluent, a computational fluid dynamics (CFD) software, and then validating the model using the classical Sod’s shock tube problem solution, as well as available shock tube experimental test results. Subsequently, the developed model is compared to a more complex 3D model in terms of the pressure, velocity and gas density. The analysis results show that there is negligible difference between the two models for axisymmetric shock tube performance simulation. However, the 3D model is necessary to simulate non-axisymmetric shock tubes. The design of a shock tube depends on the intended application. As such, extensive analyses are performed in this study, using the developed 2D axisymmetric model, to evaluate the relationships between the blast wave characteristics and the shock tube design parameters. More specifically, the blast wave characteristics (e.g. peak reflected pressure, positive phase duration and the reflected impulse), were compared to the shock tube design parameters (e.g. the driver section pressure and length, the driven v section length, and perforation diameter and their locations). The results show that the peak reflected pressure increases as the driver pressure increases, while a decrease of the driven length increases the peak reflected pressure. In addition, the positive phase duration increases as both the driver length and driven length are increased. Finally, although shock tubes generally generate long positive phase durations, perforations located along the expansion section showed promising results in this study to generate short positive durations. Finally, the developed 2D axisymmetric model is used to optimize the dimensions of a proposed large-scale conical shock tube system developed for civil infrastructure blast response evaluation applications. The capabilities of this proposed shock tube system are further investigated by correlating its design parameters to a range of explosion threats identified by different hemispherical TNT charge weight and distance scenarios. / Thesis / Master of Applied Science (MASc)

Master of Science / Department of Architectural Engineering and Construction Science / Kimberly W. Kramer / Reinforced concrete is a common building material used for blast resistant design. Adding fibers to reinforced concrete enhances the durability and ductility of concrete. This report examines how adding steel fibers to reinforced concrete for blast resistant design is advantageous. An overview of the behavior of blasts and goals of blast resistant design, and advantages of reinforced concrete in blast-resistant design, which include mass and the flexibility in detailing, are included in the blast resistant design section. The common uses for fiber-reinforced concrete, fiber types, and properties of fiber reinforced concrete varying with fiber type and length, and concrete strength are discussed in the fiber-reinforced concrete section. Two studies, Very High-Strength Concrete for Use in Blast-and-Penetration Resistant Structures and Blast Testing of Ultra-High Performance Fiber and FRP-Retrofitted Concrete Slabs, are reviewed. Lastly, the cost, mixing and corrosion limitations of using steel fiber-reinforced concrete are discussed. Reinforced concrete has been shown to be a desirable material choice for blast resistant design. The first step to designing a blast resistant reinforced concrete structure is to implement proper detailing to ensure that structural failures will be contained in a way that preserves as many lives as possible. To design for the preservation of lives, a list of priorities must be met. Preventing the building from collapse is the first of these priorities. Adding steel fibers to concrete has been shown to enhance the concrete’s post-crack behavior, which correlates to this priority. The second priority is reducing flying debris from a blast. Studies have shown that the failure mechanisms of steel fiber reinforced concrete aid in reducing flying debris when compared to conventional reinforced concrete exposed to blast loading. The major design considerations in designing steel fiber reinforced concrete for blast resistant design include: the strength level of the concrete with fiber addition, fiber volume, and fiber shape. As research on this topic progresses, the understanding of these factors and how they affect the strength characteristics of the concrete will increase, and acceptance into the structural design industry through model building codes may be possible.

<p>The main objectives of this study were to investigate (i) anovel wetland treatment technology and (ii) selected bed filtermedia for the removal of contaminants from landfill leachate. Areview of the literature concerning experiences of the use ofconstructed wetlands (CW) for the removal of nitrogen fromlandfill leachate, showed that at least three groups oftreatment systems are in practice: sub-surface flow wetlands,hybrid systems (a combination of vertical and horizontal flowwetlands) and, compact constructed wetland (CCW). Most of thesetypeswere generally effective in reducing nitrogen (N,<i>e.g.</i>NH₄-N, dominant N species in leachate) down toeffluent concentrations of about 10 mg L^-1. Unfortunately, very little evidence ofresponsible mechanisms for the removal of N was presented,although some data indicated denitrification. The treatmentperformance of a compact constructed wetland (CCW) applied atthe Tveta Landfill, Södertälje, Sweden, wasevaluated. Chemically purified leachate and untreated leachatewere applied in periods of 7 day submergence and 7 day drainageto different sections of the CCW. The removal efficiency variedbetween 40 and 82%, and a mass removal rate of up to 5.1 g m²d^-1was achieved. The chemical pre-treatment had adecisive role for the highest removal efficiencies obtained andit was unclear whether that treatment enhanced the efficiencybecause of lower toxicity and/or content of fewer competingcations. The possible combination of bed filter media and CCWas an ecotechnological treatment method for landfill leachatewas investigated by bench-scale laboratory column experiments.Reactive filter media (sorbents) was selected from their knownor suggested capacities for removal of heavy metals, nitrogenand phosphorus. Quartz sand or natural sand from an esker wasused as reference medium. Peat was used as an additionalcomponent in mixtures with the reactive media Polonite^®(product from the bedrock opoka) and blastfurnace slag (BFS). A small column study also involved zeolite.Phosphorus was efficiently removed by Polonite^®and NH₄-N to some extent. Concerning metal removal, thebest performance was found as well for Polonite^®, especially for Mn, Fe, Zn and Cu. The BFSshowed good removal efficiency for Cu, Ni and Mo. The removalof different elements was suggested to be a combination ofseveral factors,<i>e.g.</i>precipitation, ion exchange and adsorption. Priorto full-scale application of reactive filters at a landfillsite, matrix selection, filter design and operationalprocedures must be developed.</p><p><b>Keywords:</b>Blast furnace slag; Compact constructedwetland; Metals; Nitrogen; Polonite; Sorbents</p>

Approved for public release; distribution is unlimited. / During World War II many surface combatants were damaged or severely crippled by close-proximity underwater explosions from ordnance that had actually missed their target. Since this time all new classes of combatants have been required to conduct shock trial tests on the lead ship of the class in order to test the survivability of mission essential equipment in a severe shock environment. While these tests are extremely important in determining the vulnerabilities of a surface ship, they require an extensive amount of preparation, manhours, and money. Furthermore, these tests present an obvious danger to the crew on board, the ship itself, and any marine life in the vicinity. Creating a virtual shock environment by use of a computer to model the ship structure and the surrounding fluid presents a valuable design tool and an attractive alternative to these tests. This thesis examines the accuracy of shock simulation using the shock trials conducted on USS WINSTON S. CHURCHILL (DDG 81) in 2001. Specifically, all three explosions that DDG 81 was subjected to are simulated and the resulting predictions compared with the actual shock trial data. The effects of fluid volume size, mesh density, mesh quality, and shot location are investigated. / Lieutenant, United States Navy

Os cimentos de escória apresentam boas possibilidades de mercado, especialmente em aplicações em que o cimento Portland não possa ser utilizado ou onde o seu uso provoque uma elevação dos custos. A confecção de matrizes para fibras sensíveis aos álcalis e a produção de cimentos com baixo calor de hidratação são exemplos. Neste trabalho, a escória foi ativada com silicato de sódio e cal hidratada. O ativador foi formulado de maneira a proporcionar teores de Na2O de 2,5% e 5%, SiO2 de 0% a 14,8% e Ca(OH)2 de 0%, 2,5% e 5%. O aumento dos teores de Na2O e de SiO2, dentro de determinados limites, propicia um notável crescimento da resistência à compressão. Este crescimento da resistência está associado a uma diminuição da porosidade, para um mesmo fator/água aglomerante. Certamente a diminuição da porosidade é devida a um menor grau de organização cristalina dos produtos hidratados, decorrente do aumento da velocidade de precipitação de hidratados e de gel de N-C-S-H. A adição de Ca(OH)2 diminui a velocidade de perda da trabalhabilidade. Os cimentos de escória ativada com silicatos de sódio podem apresentar resistência à compressão de até 100 MPa, superior à dos cimentos Portland, com calor de hidratação da mesma ordem de grandeza. A velocidade de carbonatação destes cimentos é equivalente a dos cimentos Portland de mesma resistência. No entanto, estes cimentos apresentam maior retração hidráulica. / Binders based on ground granulated blast furnace slag (BFS) are suitable for the building industry, mainly if the use of Portland cement is expensive or may cause problems, such as: alkali sensitive fibre-reinforced cement and concretes and low heat-hydration concretes. BFS is activated by sodium silicates and hydrated lime. The compound\'s proportions are: Na2O - 2.5 and 5.0%; SiO2 from 0 to 14.8%; CaOH2 - 0, 2.5 and 5%. The increase of Na2O and SiO2 amounts allows a considerable improvement of binder strength, with values up to 100 MPa. This increase of the strength is related to the decrease of the porosity for a constant water-binder ratio. The porosity is affected certainly by the reduction of the degree of cristalynity of the hydrated compounds, due to the increase of the speed of precipitation of the hydrates or the N-C-S-H gel. It is possible to obtain BFS binders stronger than the Portland cement, with similar hydration heat. The carbonation rate of these new binders is equivalent to those of Portland cement specimens with similar strength. However these BFS binders have higher drying shrinkage.

Os cimentos de escória apresentam boas possibilidades de mercado, especialmente em aplicações em que o cimento Portland não possa ser utilizado ou onde o seu uso provoque uma elevação dos custos. A confecção de matrizes para fibras sensíveis aos álcalis e a produção de cimentos com baixo calor de hidratação são exemplos. Neste trabalho, a escória foi ativada com silicato de sódio e cal hidratada. O ativador foi formulado de maneira a proporcionar teores de Na2O de 2,5% e 5%, SiO2 de 0% a 14,8% e Ca(OH)2 de 0%, 2,5% e 5%. O aumento dos teores de Na2O e de SiO2, dentro de determinados limites, propicia um notável crescimento da resistência à compressão. Este crescimento da resistência está associado a uma diminuição da porosidade, para um mesmo fator/água aglomerante. Certamente a diminuição da porosidade é devida a um menor grau de organização cristalina dos produtos hidratados, decorrente do aumento da velocidade de precipitação de hidratados e de gel de N-C-S-H. A adição de Ca(OH)2 diminui a velocidade de perda da trabalhabilidade. Os cimentos de escória ativada com silicatos de sódio podem apresentar resistência à compressão de até 100 MPa, superior à dos cimentos Portland, com calor de hidratação da mesma ordem de grandeza. A velocidade de carbonatação destes cimentos é equivalente a dos cimentos Portland de mesma resistência. No entanto, estes cimentos apresentam maior retração hidráulica. / Binders based on ground granulated blast furnace slag (BFS) are suitable for the building industry, mainly if the use of Portland cement is expensive or may cause problems, such as: alkali sensitive fibre-reinforced cement and concretes and low heat-hydration concretes. BFS is activated by sodium silicates and hydrated lime. The compound\'s proportions are: Na2O - 2.5 and 5.0%; SiO2 from 0 to 14.8%; CaOH2 - 0, 2.5 and 5%. The increase of Na2O and SiO2 amounts allows a considerable improvement of binder strength, with values up to 100 MPa. This increase of the strength is related to the decrease of the porosity for a constant water-binder ratio. The porosity is affected certainly by the reduction of the degree of cristalynity of the hydrated compounds, due to the increase of the speed of precipitation of the hydrates or the N-C-S-H gel. It is possible to obtain BFS binders stronger than the Portland cement, with similar hydration heat. The carbonation rate of these new binders is equivalent to those of Portland cement specimens with similar strength. However these BFS binders have higher drying shrinkage.

A hipersensibilidade dentinária (HD) é descrita na literatura como uma dor aguda, de curta duração, provocada por estímulos térmico, tátil, osmótico, químico ou evaporativo em região de exposição dentinária, não sendo atribuída à dor causada pela presença de defeito ou doença de origem dentária. Esse tipo de acometimento tem sido cada vez mais reportado pelos pacientes, em vista disso, o objetivo desse estudo foi avaliar a extensão e gravidade de HD, bem como sua associação com indicadores periodontais [índice de placa (IP), índice gengival (IG) e recessão gengival (RG)] em uma amostra composta por 132 indivíduos com HD diagnosticada por meio de estímulo térmico/evaporativo (jato de ar) associada à escala Schiff. Análises descritivas foram feitas e as porcentagens médias de IP e IG foram estimadas considerando 6 sítios por dente e também 3 sítios das faces vestibulares. Além disso, os dados foram analisados através de modelos uni e multivariados utilizando análises de regressão linear. A média de idade foi de 30.66±10.33, sendo o sexo feminino mais afetado pela HD (83.3%). Foi possível observar que a HD esteve associada à recessão gengival. A prevalência de dentes com recessão gengival foi de 17.17%, enquanto que a prevalência de recessão em dentes com HD foi de 77.1% e a média de recessão vestibular foi de 1.58±0.87. Quando considerada a média de dentes com 1 ou mais milímetros de recessão, observou-se que, em média, 4.48 dos dentes apresentaram esta condição. Um maior número médio de dentes com recessão e menores escores médios de IP nos sítios vestibulares apresentaram-se signicativamente associados ao número médio de dentes com HD. A gravidade da HD nos pacientes foi significativamente influenciada por maior média de recessão gengival e foi maior nos pacientes do sexo feminino. Dentes que possuíam maiores médias de recessão e maiores escores médios de IP e menores de IG nos sítios vestibulares apresentaram maiores valores na escala Schiff (p<0.05). Frente aos achados, é possível observar que portadores de HD têm um grande número de dentes afetados por esta condição e que estes apresentam recessão. Além disto, nos dentes que apresentam HD, a gravidade desta está associada a presença de mais placa e melhor condição gengival, além da extensão da recessão. / Dentin hypersensitivity (DH) is described in the literature as an acute short-term pain caused by thermal, tactile, osmotic, chemical or evaporative stimuli in the region of dentin exposure and not attributed to pain caused by the presence of defect or disease of dental origin. Therefore, the aim of this study was to evaluate the extent and severity of DH, as well as its correlation with periodontal indicators [plaque index (PI), gingival index (GI) and gingival recession (GR)] in 132 individuals with DH diagnosed by thermal/evaporative (air blast) stimulation associated with the Schiff scale. Descriptive analyzes were made and the mean percentages of PI and GI were estimated considering 6 sites per tooth and also 3 buccal sites. In addition, the data were analyzed using univariate and multivariate models using linear regression analysis. The mean age was 30.66 ± 10.33, female sex being more affected by DH (83.3%). It was possible to observe that DH was associated to gingival recession. The prevalence of teeth with gingival recession was 17.17%, while the prevalence of recession in teeth with DH was 77.1%. The mean of vestibular recession was 1.58 ± 0.87, and when considered the mean teeth with 1 or more millimeters recession, it was observed that, a mean of 4.48 teeth presented this condition. A higher mean number of teeth with recession and lower mean PI scores in the vestibular sites were associated (p<0.001) with the mean number of teeth with DH. The severity of DH in number of patients was significantly influenced by the higher mean of gingival recession and was higher in the female patients. Teeth that had higher recession mean and higher mean PI scores at the buccal sites, but lower GI scores at this sites, presented significantly higher values on the Schiff scale (p <0.05). In view of the findings, it is possible to observe that DH patients have a large number of teeth affected by this condition and that these present gingival recession. In addition, in the teeth that present DH, the severity is associated with the presence of more plaque and better gingival condition, in addition to the extent of the recession.

Traumatic brain injury (TBI) is a serious public health concern. Although moderate and severe forms of TBI receive considerable attention, mild TBI accounts for the majority of all injuries. The first two aims of this work used a rodent model of mild blast to simulate primary injury (damage from the blast wave only). The first aim evaluated potential changes in interneurons containing the calcium-binding proteins calretinin or parvalbumin. In addition, morphological changes in astrocytes and microglia were assessed. Brains were analyzed 48 hours and one month following exposure to single or repeated blasts, with a focus on the hippocampus due to its integral role in learning and memory. Results showed significant region-specific alterations in microglia morphology 48 hours following blast. The absence of structural alterations in microglia one month following blast indicated that the regional hippocampal vulnerability may be transient. The second aim compared glial morphologies in the retina and brain (the lateral geniculate nucleus, superior colliculus, and visual cortex) 48 hours or one month following multiple blasts. Fiber degeneration has received considerable attention, however, less is known about the status of glia throughout the visual pathway following mild blasts. Although no structural alterations were detected, it is possible that alterations in glia occurred at a more acute time scale as changes in glia can be rapid and reversible. The final aim of this work focused on the immunocytochemical characterization of tau pathology in the visual cortices of human postmortem brains with advanced chronic traumatic encephalopathy (CTE). CTE is a devastating tauopathy associated with mild, repetitive TBIs. Although visual deficits are reported in CTE, the primary visual cortex is often spared. The main hypothesis under investigation was whether visual association areas would have tau pathology, despite sparing of primary visual cortex. In addition, a sub-class of interneurons containing parvalbumin was used to evaluate a potential cell-specific vulnerability. Results showed increased tau pathology in visual association areas in advanced CTE, that was largely absent from the primary visual cortex. There was no effect on parvalbumin positive interneurons. The results of this work provides valuable insight regarding potential cell-specific resistance to CTE pathology. / 2018-11-03T00:00:00Z