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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Mechanisms of Blister Formation on Concrete Bridge Decks with Waterprooving Asphalt Pavement Systems

Hailesilassie, Biruk Wobeshet January 2013 (has links)
Bridge decks are commonly subjected to harsh environmental conditions that often lead to serious corrosion problems triggered by blisters under the hot mix asphalt bridge deck surfacing and secretly evolving during weather exposure until damage is often detected too late. Blisters may form under both the waterproofing dense mastic asphalt layer or under the waterproofing membrane which is often applied as additional water protection under the mastic asphalt (MA). One of the main technical issues is the formation of blisters under the membrane and asphalt-covered concrete structures caused by a complex mechanism governed by bottom-up pressure and loss of adhesion. A linear viscoelastic finite-element model was developed to simulate time-dependent blister growth in a dense mastic asphalt layer under uniformly applied pressure with and without temperature and pressure fluctuation. A finite element model was developed using ABAQUS with linear viscoelastic properties and validated with a closed form solution from first-order shear-deformation theory for thick plates. In addition, the blister test was conducted on different samples of MA in the laboratory and digital image correlation measurement technique was used to capture the three-dimensional vertical deflection of the MA over time. It was found that the blister may grow continuously under repeated loading conditions over subsequent days. With respect to blistering under waterproofing membranes, mechanical elastic modeling and experimental investigations were performed for three different types of membranes under in-plane stress state. The orthotropic mechanical behavior of a polymer modified bitumen membrane (PBM) was determined from biaxial test data. Finally, blister tests by applying controlled pressure between orthotropic PBMs and concrete plates were performed for studying the elliptical adhesive blister propagation using digital 3D image correlation. The energy calculated from elliptical blister propagation was found comparable to the adhesive fracture energy from standard peeling tests for similar types of PBMs. This indicates that the peeling test assists to evaluate and rank the adhesive properties of different types of membranes with respect to blister formation at room temperature without conducting time consuming and complicated pressurized blister propagation tests using digital 3D image correlation. / <p>QC 20130625</p>
52

Mechanická odolnost povlakových hydroizolací vůči poškození prvky konstrukční ochrany hydroizolace / Mechanical durability of waterproofing membranes against elements of waterproofing membrane construction protection

Remeš, Josef January 2018 (has links)
Waterproofing membranes are one of the most commonly used waterproofing insulation materials. These can be found both in assemblies of roof constructions and substructures and are a key component for waterproofing systems. During design process it is necessary to select materials, elements and accessories so that mutual compatibility, waterproof effectiveness and reliability is ensured. In order to protect the main waterproofing layer a composition is therefore completed with construction protection elements, which are meant to prevent from a mechanical damage of waterproofing membrane. Mechanical stress and damage may become evident in variety of situations, which can be caused externally not only as an inappropriate ground bashing procedure but also as a consequence of improper waterproofing construction protection. In practice there are many cases of waterproofing system failures due to stress of elements with higher mechanical durability which affect elements with lower mechanical durability. The dissertation deals with an application of dimpled membranes protected by the layer of waterproofing membranes, which may due to stress and mutual compatibility result in waterproofing system failure and waterproofing reliability decrease. The dissertation is focused on mechanical durability of waterproofing membranes made of folio and modified bitumen membrane against damage from dimple membrane depending on stress category. First, possible waterproofing membrane damage from dimple extrusion is calculated and evaluated. The next part deals with verifying by experiment based on an effect of long-term static stress and short-term dynamic stress caused by ground bashing, where a measurement of ground bashing stress is performed. Experiment interpretation and an acquired knowledge provided the dissertation with an information what combination and order of particular layers results in higher risk of waterproofing system failure and waterproofing reliability decrease
53

AN INVESTIGATION INTO THE DESIGN AND PRODUCTION OF THE SINGLE-POUR, CAST-IN-PLACE CONCRETE COMPOSITE WALL

STEVENS, BENJAMIN JOHN 02 July 2004 (has links)
No description available.
54

Compatibilité tribologique d’un revêtement de surface avec une application donnée : Cas d’un revêtement de WS2 sur une tige de piston de frein aéronautique / Tribological compatibility of a surface coating with a given application : Case of the WS2 coating on a piston road of a landing gear braking system

Tsala Moto, Serge Parfait 29 May 2017 (has links)
Le chrome dur, utilisé comme revêtement de tige d’actionneurs hydrauliques linéaires, a été interdit pour risque sanitaire (directive européenne REACH). A cet effet, un revêtement de WS2 a été sélectionné par Safran Landing Systems pour substituer le chrome dur comme revêtement de tige de piston de frein hydraulique. La démarche de sélection utilisée, est limitée par son incapacité à expliquer les performances observées et démontre le besoin d’une démarche de sélection d’autant plus appropriée que la notion d’étanchéité des actionneurs hydrauliques linéaires est « floue ». Comme, la tribologie n’a pas vocation à caractériser les revêtements de surface, parce que son plus petit objet d’étude est un triplet tribologique, cette étude propose l’évaluation de la compatibilité tribologique du revêtement de WS2, avec la fonction d’étanchéité. La démarche utilisée montre que l’étanchéité est régie, par un critère en pression, et par une vérification des caractéristiques tribologiques du système tige/joints requises pour la réalisation de l’étanchéité ; ce qui nécessite un piston hydraulique instrumenté. L’absence de ce piston est compensée par une « caractérisation tribologique approchée » du contact tige/joints, qui associe les expertises tribologiques de pistons hydrauliques d’essais de qualification, appuyées par un modèle éléments finis (EF) du piston hydraulique d’une part, et les résultats d’un essai de frottement piste/joints, conçus à cet effet à l’aide d’un modèle EF d’autre part. Les résultats montrent que le système tige/joints présente de bonnes caractéristiques tribologiques pour le facteur de frottement et l’usure, alors que la localisation de l’accommodation de vitesses dans le cas du contact tige/joint d’étanchéité, accélère le débit source du revêtement et limite sa durée de vie. Enfin, cette thèse comble un vide méthodologique en proposant, une démarche de sélection d’un revêtement pour une application tribologique, et une démarche de triboconception d’un actionneur hydraulique linéaire dans le cas d’un fonctionnement quasi-statique. / Hard chromium used as rod coating in linear hydraulic actuators has been forbidden by the European Directive REACH. In this situation, a WS2 coating has been selected by Safran Landing Systems to replace the hard chromium coating on rod pistons actuators of landing gear braking systems. The selection method was unable to explain the observed performance, and shows the lack of an appropriate methodology for the rod coating selection, mainly because the sealing concept is rather vague. Since tribology is not intended to characterize surface coatings, because its smallest object of study is a tribological triplet, this study proposes the evaluation of the tribological compatibility of the WS2 coating with the sealing function of the hydraulic piston. The adopted approach shows that the sealing performance is governed by a rod/seal contact pressure criterion and by the verification of the tribological characteristics of the rod/seal contact required to achieve a sealing performance. This tribological characterization requires an instrumented hydraulic piston. The absence of this piston is compensated by an "approximate tribological characterization" of the rod/seal contact, which combines the tribological expert analysis of hydraulic pistons of qualification tests, supported by a finite elements model (FE) of the hydraulic piston, and the results of a plate rod/seal friction test, designed for this purpose using another FE model. The results show that the rod/seal contact exhibits good tribological characteristics for the friction factor and wear, whereas the location of the velocity accommodation in the case of the rod/anti-extrusion seal contact accelerates the 3rd body generation of the coating and limits its life expectancy. Finally, this thesis fills a methodological lack by proposing a method of selecting a coating for a tribological application and a triboconception method of a linear hydraulic actuator in the case of quasi-static operating conditions.
55

Influência de adições minerais e aditivo impermeabilizante interno no desempenho de telhas protendidas pré-fabricadas em concreto

Silva, Patricia Ribeiro da 28 April 2011 (has links)
Com o surgimento da tecnologia da pré-fabricação, a construção civil tem adquirido elevada agilidade, reduzindo os prazos de construção e maior qualidade no controle de execução. Dentre as diversas peças pré-fabricadas, a telha em concreto protendido autoportante tem por característica cobrir vãos de até 25 m, sem a existência de estrutura de apoio intermediária. Sendo um produto esbelto, exige um aprimoramento constante para aumentar a durabilidade da estrutura quanto à corrosão da armadura e manter sua adequação ao uso. O objetivo desse trabalho é reduzir a permeabilidade das telhas pré-fabricadas, além de analisar a influência desse parâmetro na durabilidade do concreto frente às classes de agressividade da norma NBR 9062/2006. A norma estabelece um fator a/c máximo de 0,45 e resistência característica à compressão mínima de 40 MPa, enquadrando-se como classe de agressividade ambiental II - Urbana. Para tal, foram escolhidas algumas adições minerais existentes na região da grande Curitiba (metacaulim e filler), além de um aditivo impermeabilizante interno, comparando com o traço de referência preexistente em linha de produção. As dosagens foram definidas com base no empacotamento de partículas e caracterizadas quanto à resistência mecânica à compressão, absorção de água por imersão e por capilaridade e, penetração de água sob pressão, além dos ensaios de porosimetria por intrusão de mercúrio (PIM), carbonatação e penetração de íons cloreto. Em termos de resistência mecânica à compressão, a dosagem referência apresentou os melhores resultados (em função da menor relação água/cimento e maior consumo de cimento), seguido pelo concreto com aditivo impermeabilizante e com metacaulim. Para a absorção de água, todas as dosagens apresentaram-se como concretos duráveis, com destaque para o metacaulim e filler+aditivo impermeabilizante. Quanto à absorção capilar, todas as dosagens apresentaram baixa permeabilidade. Para a penetração de água sob pressão todas se apresentam como impermeáveis em condições agressivas, com destaque para o uso do metacaulim e do aditivo impermeabilizante. O ensaio de PIM mostra que a dosagem com filler possui uma concentração maior de poros e que a dosagem com metacaulim apresenta o menor diâmetro máximo de poros, com uma tendência ao refinamento em diâmetros menores. Quando analisado o resultado de carbonatação, o metacaulim apresentou o melhor resultado, possibilitando um menor cobrimento da armadura para uma vida útil de 50 anos. Quanto à penetração de cloretos, a dosagem com metacaulim, apresentou uma redução maior em relação às demais dosagens pela sua atividade pozolânica, contribuindo para a durabilidade do concreto. Em linhas gerais, é possível melhorar a impermeabilidade do concreto com o acréscimo de 8% do metacaulim sobre o peso do cimento, ainda com uma redução de 5,2% de cimento, com bons resultados também para o uso de 1% de aditivo impermeabilizante. Quanto à durabilidade, a otimização da curva granulométrica dos agregados e o uso do metacaulim possibilitam a utilização de telhas pré-fabricadas em regiões de classe de agressividade III - Industrial ou Marinha, observando o cobrimento mínimo da armadura. / With the emerging precast concrete technology, the civil construction has acquired high agility, reducing construction time and greater quality control in execution. Among several precast pieces, tile in prestressed concrete is characterized by selfsupporting spans of up to 25 m, without the existence of an intermediate support structure. Being a slim product, requires an improvement in increasing the durability of the structure because of the steel corrosion and maintain their fitness for use. The objective of this research is to reduce the permeability of the precast tiles, and analyzing their influence in the durability of the concrete face of the aggressiveness classes constants in the NBR 9062/2006, that establish the a/c ratio up to 0,45 and minimum compressive strength characteristic of 40 MPa, positioning themselves as a class of environmental aggressiveness II - Urban. For this, were selected a few mineral admixture from Curitiba/Paraná and a waterproof internal admixture, comparing with the concrete mix pre-existing in production line. The concrete dosages were defined by packing particles and were analysed for mechanical compressive strength, water absorption by immersion and by capillarity and water penetration under pressure, in addition to tests of mercury intrusion porosimetry (MIP), carbonation and chloride ion penetration. About the mechanical compressive strength, the dosage reference showed the best results (due to lower water / cement ratio and higher cement consumption), followed by concrete with waterproofing admixture and metakaolin. For water absorption, all measurements fall as durable concrete, especially the metakaolin additive and filler + waterproofing. For the water absorption, all dosages presented low permeability. For the water penetration under pressure all fall as impervious to several conditions, especially with metakaolin and waterproofing admixture. The MIP test shows that the dosage with filler has a higher concentration of pores and the dosage with metakaolin has the smallest maximum diameter of pores, with a tendency towards refinement in smaller diameters. When analyzing the carbonation, the metakaolin showed the best results, allowing a smaller reinforcement cover for a lifetime of 50 years. As the penetration of chlorides ions, the metakaolin, showed a greater reduction comparing with other dosages for its pozzolanic activity, contributing to the concrete durability. In general, it is possible to improve the concrete impermeability with the addition of 8% of metakaolin by weight of cement, with 5,2% of cement reduction, showing good results also using 1% of waterproofing admixture. As for durability, the optimizing of aggregates granulometric curve and the use of metakaolin enables the use of prefabricated tiles in regions of class of environmental aggressiveness III - Industrial or Marine, observing the minimum concrete cover of reinforcement.
56

Método para dimensionamento eficiente de reservatórios de contenção de cheias para a cidade de Curitiba-PR / Method for efficient sizing of flood detention tanks for the city of Curitiba-PR

Souza, Ricardo Cesar Conrado de 09 March 2018 (has links)
Os impactos causados por precipitações em áreas urbanas indicam a necessidade da abordagem de medidas para gerenciamento da drenagem urbana, de modo a evitar prejuízos originados dos escoamentos superficiais, como as inundações. A drenagem urbana brasileira é considerada defasada, visto que o conceito da canalização prevalece sobre a reservação e a infiltração, priorizando o rápido escoamento ao invés do descarte controlado dos volumes reservados. A cidade de Curitiba-PR conta com o Decreto Municipal Número 176/2007, responsável pelos critérios para implantação dos mecanismos de contenção de cheias. Porém, as diretrizes de projeto estabelecidas não garantem eficiência mínima para os reservatórios de contenção, visto que a mesma pode variar em função da sua área de base, lâmina de água e diâmetro do orifício regulador de vazão. Nesta pesquisa é proposto um método de dimensionamento, estabelecendo critérios que relacionam as áreas impermeabilizadas dos lotes aos parâmetros de dimensionamento dos reservatórios, garantindo a função desta medida de controle. Considerando que os reservatórios devem proporcionar à dada área impermeabilizada retornar à sua condição de pré-urbanização em termos de vazões de contribuição, estima-se o valor necessário para a redução de vazão de pico em 70,24%, obtido da relação entre os coeficientes de escoamento superficial em ambas as condições de impermeabilização. A partir de simulações de propagação de vazão com o Método de Pulz em áreas impermeabilizadas genéricas em intervalos constantes adotados para o estudo, são obtidos gráficos das características geométricas dos reservatórios em função da vazão de contribuição que cada área genérica recebe. A partir da análise comportamental dos mesmos são propostas equações de dimensionamento para os parâmetros de volume, área de base, altura da lâmina de água e diâmetro do orifício regulador de vazão, relacionando-os às áreas impermeabilizadas presentes, de modo que seja garantida a eficiência mínima necessária. Ao comparar os resultados obtidos com o previsto na legislação municipal, além da possibilidade de melhoria na eficiência dos reservatórios com a utilização de outros parâmetros de dimensionamento, há condição de redução de 24,14% do volume em relação ao cálculo atual. / The impacts caused by rainfall in urban areas indicate the need to approach measures for managing urban drainage, in order to avoid losses arising from runoff, such as floods. Brazilian urban drainage is considered outdated, because the concept of channeling is more used than the reservation and infiltration, prioritizing fast flowing instead of controlled disposal of reserved volumes. The city of CuritibaPR has a Municipal Decree Number 176/2007, responsible for the criteria for implementation of flood containment mechanisms. However, the established design guidelines do not guarantee minimum performance for flood detention tanks, since it may vary depending on their base area, water depth and flow regulator’s orifice diameter. In this research is proposed a sizing method, establishing criteria that relate waterproofed areas of the lots to the tank design parameters, ensuring the function of this control measure. Considering that tanks must provide the given waterproofed area return to its condition before urbanization in contributing flows, determine the value of the required peak flow reduction in 70,24%, obtained from the relation between the coefficients of runoff in both waterproofing conditions. From flow propagation simulations with Pulz Method in generic waterproofed areas at constant intervals adopted for the research, graphs of the geometric characteristics of the reservoirs are obtained as a function of the contribution flow that each generic area receives. From the behavioral analysis, sizing equations are proposed for the parameters of volume, base area, water depth and flow regulator’s orifice diameter, relating them to the present waterproofed areas and ensuring the required efficiency. When comparing the results obtained with the provisions of municipal legislation, in addition to the possibility of improving the efficiency of the reservoirs using other sizing parameters, it points to the possibility of reducing the calculated volume of 24,14% in relation to the current calculation.
57

Analýza přídržnosti hydroizolačních systémů ze samolepicích asfaltových pásů / Analysis of adhesion of waterproofing systems of self-adhesive asphalt felts

Kerekanič, Robin January 2018 (has links)
This diploma thesis focuses on the adhesive of asphalt felts on flat roofs. The practical part evaluates on the basis of experiments the adhesion of self-adhesive asphalt felts on conventional system with warm deck. It proposes and experimentally verifies the method for temperature cycling of samples and the system for causing condensation under bitumen sheet. The influence of temperature and humidity on the adhesion of the bitumen sheet during the realization, the subsequent effects of these influences as well as the condensation test are monitored by static loading. The influence of the dynamic load on the adhesion of the waterproofing to expanded foamed polystyrene is also tested. In the discussion and conclusion, the influence of the human factor on the resulting adhesion and the suitability of the methods used are also assessed.
58

Rekonstrukce železničního tunelu / Reconstruction of the railway tunnel

Nekl, Jiří January 2013 (has links)
The diploma thesis engages in the reconstruction of railway tunnel Domasovsky that is situated at the track section Olomouc – Krnov. It illustrates the current state of the construction and the geotechnical conditons of the area of interest, it also presents the potencial solutions. The design is verified by stuructural analysis, the design documentation and technical report are also enclosed.
59

Mechanicky kotvené povlakové hydroizolace / Systems of mechanically fastened flexible roof waterproofing membranes

Stodůlka, Jindřich January 2014 (has links)
The aim of this thesis is going to concentrate on the issues associated with the technology of mechanically anchored coating waterproofing of roofs. Today the mechanical anchoring belongs to the most widespread way of how to stabilize the layers of roofing material against the effects of wind uplift particularly in indoor buildings. However some malfunctions occur more and more frequently which cause leaking into the constructions or even the destruction of the whole roof in the worse cases. The practical part of this thesis is going to concentrate on the fasterners which belong to the most important elements of the mechanical anchored system. The aim of the experimental measurement is to draw a comparison of the quality of fasteners which are distributed on the Czech market. Thereafter the obtained figures are going to be compared with the theoretical calculating procedures according to the valid designed standards.
60

Laboratorní testování účinnosti hydroizolačních injektážních gelů v závislosti na stavu různých stavebních materiálů / Laboratory testing of hydroinsulating injection gel´s efficiency in dependence on state of various building materials

Miková, Lenka January 2015 (has links)
Nowadays the use of chemical gel injection for humid masonry provides many benefits. If we consider the financial aspects of this kind of remediation of humid masonry, we can say that this method is least expensive and time-consuming. In comparison with other remediation methods major interventions into the structure is not required, which could result in deterioration of the structural analysis of the works and the consequent need of special machinery, which subsequently increases spent effort and resources. There is also need for additional screens easily applied to walls breached by rising damp and this need is also required for research in dealing with this issue. Only a standard regulation dealing with remediation of wet masonry using chemical injection is directive WTA 4-4-04 / D – Injection of masonry against capillary moisture. From this point of view there is a clear need for further development in this area.

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