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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.
121

Coffee and Conflict: Veteran Antiwar Activity and G.I. Coffeehouses in the Vietnam Era

Walls, Harley Elisabeth Noelle 25 April 2022 (has links)
No description available.
122

Půdorysně zakřivená oblouková lávka pro pěší / Plan curved arch footbridge

Trenz, Jan January 2012 (has links)
The scope of thesis is to design a curved arch footbridge. The main structure consists of composite deck supported by steel arch. The focus is on finding optimal shape of arch and proper cross-sections of elements. Bridge is analysed according to limit states.
123

Armering i pålfundament : Effektivare byggprojektering med grafisk programmering / Reinforcement of Pile Caps : Increased Efficiency of Structural Design with Visual Programming

Schmied, August, Strömberg, Moa January 2019 (has links)
En stor del av projekteringsskedet är framtagandet av bygghandlingar, främst ritningar i 2D. En modernare metod är istället att samla all information om ett byggnadsprojekt i en samordnad 3D-modell, så kallad BIM-modell. Building Information Modeling (BIM) är en välkänd projekteringsmetod som bygger på att digitala 3D-modeller innehåller tillräcklig information för att beställas och produceras i fysisk form. Modellen består av parametrar som representerar olika egenskaper och när en parameter ändras uppdateras modellen automatiskt. Parametrarna kan nås och modifieras av insticksprogram, så kallade plug-ins som utökar den ursprungliga programvarans funktionalitet med hjälp av programkod. Grafisk programmering är en modern programmeringsmetod med ett visuellt gränssnitt som underlättar för oerfarna användare. Med hjälp av grafisk programmering kan parameterstyrning av 3D-modeller effektiviseras och värdefull tid sparas. Av denna anledning har Dynamo, ett plug-in utvecklat av företaget Autodesk för Revit, studerats för att ta fram ett så kallat skript som automatiserar 3D-modelleringsprocesser i Revit kopplat till placering av armering i pålfundament. Dessutom har möjligheter till standardisering undersökts, samt för- och nackdelar med metoden. I detta examensarbete redogörs för potentialen med Dynamo och de skript som skapats genom en empirisk studie. En enklare fallstudie utfördes för att kunna åskådliggöra graden av tidsbesparing gentemot motsvarande arbete manuellt i Revit. För att komplettera armeringsskripten togs beräkningsmallar fram som, enligt fackverksmetoden och Eurokod 2, försåg skripten med korrekt indata. Resultatet av projektet visar på att Dynamo och grafisk programmering kan effektivisera armeringsplacering i pålfundament. Graden av effektivisering beror på varje enskilt fall, men fallstudien visade på ca 85–90% sparad tid. En generell slutsats pekar mot att ju mer komplicerad utformning av armering desto mer tid finns att spara. Då grafisk programmering bygger på automatisering av arbetsprocesser av upprepande karaktär finns stor potential för att standardisera projektering med hjälp av dynamoskript. Företag kan då skapa rutiner som ökar kontinuitet och kvalitet i sina projekt. Automatiseringen leder även till färre mänskliga fel och utförandet blir effektivare. Uppdragsgivaren uppmanas att vidareutveckla metoden genom att implementera tydliga rutiner vad gäller 3D-modellering med grafisk programmering, samt undersöka möjligheten med automatiserad armering i andra bärande konstruktioner. / Most of the time spent on project planning is dedicated to the development of construction documents, mainly 2D-drawings. A more modern method is to gather all information about a building project in a coordinated 3D-model, so called BIM-model. Building information modelling (BIM) is a well-known design method based on a digital 3D model having enough information to enable procurement work and actual production. The model consists of parameters that represent different properties and when a parameter is changed, the model is updated automatically. These parameters can be accessed and modified through external programs, so called plug-ins that extend the original software’s functionality using program code. Visual programming is a modern programming method which utilizes a visual interface that favours users with little or no experience. Using visual programming, parameter control can be made more efficient and save valuable time. For this reason, Dynamo (a plugin developed by the company Autodesk for Revit), has been studied to create a so-called script that automates 3D modelling processes in Revit linked to placement of reinforcement in pile caps. In addition, possibilities for standardization have been investigated, as well as the advantages and disadvantages of the method. With this project, the potential of Dynamo and the scripts created through an empirical study is described, where a relatively simple case study is carried out in order to illustrate the amount of time saved through visual programming compared to corresponding work manually done in Revit. Furthermore, calculation templates were created, according to the strut and tie model and Eurocode 2, to provide the script in Dynamo with the correct inputs. The result shows that Dynamo and visual programming can make placement of reinforcement in pile caps more efficient. While the degree of efficiency is case dependent, the case study showed an overall 85-90% time saving. A general conclusion suggests that the more complicated rebar designs, the more time there is to be saved. Since visual programming is based on the automation of repetitive processes, there is great potential to standardize structural design with the help of Dynamo scripts. Companies can thus create routines that increase continuity and quality in their projects. The automation also leads to fewer human errors and a more efficient execution. The client is advised to further develop this method by implementing explicit routines regarding 3D modelling with visual programming and investigate the possibilities of automation of reinforcement design in other load-bearing structures.
124

Estudio de 2 edificaciones aporticadas considerando los efectos de la interacción tabique pórtico mediante el método del puntal equivalente / Study of 2 buildings considering the frame-masonry interaction by the equivalent strut method

Anaya Saldaña, Christian Alejandro, Asencio Huamanchay, Medali Del Carmen 26 August 2021 (has links)
La tabiquería a pesar de estar aislada aporta cierta rigidez lateral a los pórticos como se demostró en el estudio de (Zhou, Kou, Peng, & Cui, 2018), por lo cual, se debe realizar en algunos casos un análisis considerando la interacción tabique pórtico En la primera parte de la tesis se evaluó que características de un pórtico son las más influyentes en el ancho efectivo (Wb) del puntal equivalente a partir de un análisis con el método de elementos finitos, donde se encontró que la longitud diagonal del pórtico es la variable más influyente. Luego en la segunda parte se realizó un análisis sísmico de 2 edificaciones que fueron predimensionadas con la deriva máxima y 50% de la deriva máxima de la norma E0.30. Estos 4 modelos se analizaron con tabiquería y sin tabiquería, con el método modal espectral y tiempo historia. Las principales conclusiones fueron que realizar un análisis considerando la ITP puede cambiar el comportamiento modal de la edificación, la cortante basal aumentó hasta en un 19.5% en la estructura rígida y 17% en la flexible, los desplazamientos laterales se redujeron en máximo el 53% en la estructura flexible y 16% en la rígida, y que el periodo disminuyó hasta un 25%. Se concluyó que una edificación más flexible amplifica las diferencias entre el modelo con ITP y sin ITP. Por último, se confirmó que el análisis considerando la ITP saca a la luz irregularidades por torsión y/o piso blando que no se encuentra en un análisis convencional. / The masonry wall, despite being isolated, provides a certain lateral stiffness to the frames, as demonstrated in the study by (Zhou, Kou, Peng, & Cui, 2018), therefore, in some cases an analysis must be carried out considering the masonry walls. In the first part of the thesis, it was evaluated which characteristics of a frame are the most influential in the effective width (Wb) of the equivalent prop from an analysis with the finite element method, where it was found that the diagonal length of the frame is the most influential variable. Then, in the second part, a seismic analysis of 2 buildings was performed that were pre-dimensioned with the maximum drift and 50% of the maximum drift of the E0.30 standard. These 4 models were analyzed with masonry and without masonry, with the spectral modal method and time history. The main conclusions were that carrying out an analysis considering the ITP can change the modal behavior of the building, the basal shear increased by up to 19.5% in the rigid structure and 17% in the flexible one, lateral displacements were reduced by a maximum of 53% in the flexible structure and 16% in the rigid structure, and that the period decreased to 25%. It was concluded that a more flexible building amplifies the differences between the model with ITP and without ITP. Finally, it was confirmed that in the analysis considering the ITP there are irregularities due to torsion and / or soft story. / Tesis
125

Behaviour of continuous concrete deep beams reinforced with GFRP bars

Shalookh, Othman H. Zinkaah January 2019 (has links)
This research aims to investigate the behaviour of glass fibre reinforced polymer bars (GFRP) reinforced continuous concrete deep beams. For this purpose, experimental, analytical and numerical studies were conducted. Nine continuous concrete deep beams reinforced with GFRP bars and one specimen reinforced with steel bars were experimentally tested to failure. The investigated parameters included shear span-to-overall depth ratio (𝑎/ℎ), size effect and web reinforcement ratio. Two 𝑎/ℎ ratios of 1.0 and 1.7 and three section heights of 300 mm, 600 mm and 800 mm as well as two web reinforcement ratios of 0% and 0.4% were used. The longitudinal reinforcement, compressive strength and beam width were kept constant at 1.2%, ≈55 MPa and 175 mm, respectively. The web reinforcement ratio achieved the minimum requirements of the CSA S806-12. The experimental results highlighted that the web reinforcement ratio improved the load capacities by about 10% and 18% for specimens having 𝑎/ℎ ratios of 1.0 and 1.7, respectively. For specimens with web reinforcement, the increase of 𝑎/ℎ ratio from 1.0 to 1.7 led to reductions in the load carrying capacity by about 33% and 29% for beams with overall depths of 300 mm and 600 mm, respectively. Additionally, a considerable reduction occurred in the shear strength due to the increase of the section depth from 300 mm to 600 mm. The experimental results confirmed the impacts of web reinforcement and size effect that were not considered by the strut-and-tie method (STM) of the only code provision, the Canadian S806-12, that addressed such elements. In this study, the STM was illustrated and simplified to be adopted for GFRP RC continuous deep beams, and then, the experimental results obtained from this study were employed to assess the performance of the effectiveness factors suggested by the STMs of the American (ACI 318-2014), European (EC2-04) and Canadian (S806-12) codes as well as those factors recommended by the previous studies to predict the load capacities. It was found that these methods were unable to reflect the influences of member size and/or web reinforcement reasonably, the impact of which has been confirmed by the current experimental investigation. Therefore, a new effectiveness factor was recommended to be used with the STM. Additionally, an upper bound analysis was developed to predict the load capacities of the tested specimens considering a reduced bond strength of GFRP bars after assessing the old version recommended for steel RC continuous deep beams. A good agreement between the predicted results and the measured ones was obtained with the mean and coefficient of variation values for experimental/calculated results of 1.02 and 5.9%, respectively, for the STM and 1.03 and 8.6%, respectively, for the upper-bound analysis. A 2D finite element analysis using ABAQUS/Explicit approach was carried out to introduce a model able to estimate the response of GFRP RC continuous deep beams. Based on the experimental results extracted from the pullout tests, the interface between the longitudinal reinforcement and concrete surface was modelled using a cohesive element (COH2D4) tool available in ABAQUS. Furthermore, a perfect bond between the longitudinal reinforcement and surrounding concrete was also modelled to evaluate the validity of this assumption introduced by many previous FE studies. To achieve a reasonable agreement with the test results, a sensitivity analysis was implemented to select the proper mesh size and concrete model variables. The suitability and capability of the developed FE model were demonstrated by comparing its predictions with the test results of beams tested experimentally. Model validation showed a reasonable agreement with the experiments in terms of the failure mode, total failure load and the load-deflection responses. The perfect bond model has overestimated the predicted results in terms of stiffness behaviour and failure load, while the cohesive element model was more suitable to reflect the behaviour of those specimens. The validated FE model was then employed to implement a parametric study for the key parameters that govern the behaviour of beams tested and to achieve an in depth understanding of such elements. The parametric study showed that the higher the 𝑎/ℎ ratio the more pronounced the effect of web and the longitudinal reinforcements and the lower the effect of concrete compressive strength; and vice versa when 𝑎/ℎ ratio reduces.
126

Συμβολή στην αναλυτική και πειραματική μελέτη φέρουσας τοιχοποιίας ενισχυμένης με σύνθετα υλικά / Contribution to the analytical and experimental investigation of masonry structures strengthened with composites materials (FRP)

Κρεβάικας, Θεοφάνης 24 June 2007 (has links)
Γίνεται μια γενική ανφορά στο πρόβλημα της ενίσχυσης φέρουσας τοιχοποιίας με σύνθετα υλικά και παρουσιάζονται οι μέχρι τώρα τεχνικές και τρόποι εφαρμογής της μεθόδου. Στη συνέχεια αναπτύσεται λογισμικό το οποίο συνδιάζει την χρήση των πεπερασμένων στοιχείων και των προσομοιωμάτων θλιπτήρων-ελκυστήρων για την σύνθεση του τασικού πεδίου μεμονομένων δομικών στοιχείων Φ.Τ. Αντικειμενικός σκοπός είναι η σύνθεση ενός δικτυώματος από την επίλυση του οποίου να προκύπτει η τοπολογία των οπλισμών και η εκτίμηση του απαιτούμενου εμβαδού σύνθετου υλικού. Παρουσιάζονται τα πειραματικά αποτελέσματα που έχουν προκύψει απο δοκίμια περισφιγμένα διαφόρους τύπους σύνθετου υλικού, για διαφορετικά γεωμετρικέ χαρακτηριστικά και ποσότητες οπλισμού, καθώς και υλικό εμποτισμού. Βαθμονομείται ένα αναλτυικό προσομοίωμα για την περισφιγμένη τοιχοποιία με σύνθετα υλικά. Καταστρώνονται οι εξισώσεις σχεδιασμού Φ.Τ. ενισχυμένης με σύνθετα υλικά για τις κλασσικές περιπτώσεις καταπόνησης και συντίθεται λογισμικό που χρησιμοποιεί τις εξισώσεις αυτές. / Strengthening of masonry structures with FRPs. A general overview of the method and presentation of all the related topics that are known until today. Evaluation of a software that combines the finite element method with the strut-and -tie models in the composition of the stress field of a given load bearing masonry element. The purpose of the method is to compose a truss, from the given stress field, in order to identify the topology of the reinforcment (FRP strips), as well as the amount of the strips needed to be placed in the positions of the struts. Experimental investigation of the confined masonry with FRPs. Presentation of the experimental data using specimens with various b/h ratios confined with different type of fibers, layers of reinforcement, smoothening radious of the corners and with different type of impregnation materials. Synthesis of the equations governing the most important cases of strengthening masonry structures with FRPs and composition of a software for the design of such cases.
127

Magnetorheological Strut for Vibration Isolation System of Space Launcher / Magnetorheological Strut for Vibration Isolation System of Space Launcher

Macháček, Ondřej January 2018 (has links)
Práce se zabývá návrhem magnetoreologické (MR) vzpěry vibroizolačního systému (VIS) pro kosmický nosič. V rešeršní části jsou popsány vybrané VIS a vzpěry těchto systémů, které byly v kosmických nosičích využity v minulosti. Každá z těchto vzpěr obsahující kapalinu byla těsněna pomocí statických těsnění a pružných vlnovců vyrobených z oceli. Důkladněji byla analyzována vzpěra pasivního systému VIS s označením ELVIS, jehož konstrukce se stala inspirací pro tuto práci. Jedná se o tříparametrický systém, v němž je tlumič uložen na pružině, jejíž tuhost přibližně odpovídá objemové tuhosti vlnovců respektive jejímu průmětu do axiálního směru (pressure thrust stiffness). V práci je představena metodika pro stanovení “pressure thrust stiffness” na základě geometrie vlnovce a také uvedeny parametry vlnovce díky kterým je možné měnit poměr mezi axiální a “pressure thrust stiffness” vlnovce. Tento poměr ovlivňuje v dané koncepci vzpěry její dynamické chování a tím i chování celého VIS. Pro predikci dynamického chování vzpěry byl vytvořen multi-body model VIS založeného na Stewartově plošině a detailnější model jediné vzpěry. Simulace provedené v tomto modelu odhalily parametry, které mají vliv na výkonost tlumiče ve VIS: časová odezva a dynamický rozsah. Díky modelu byl určen rozsah těchto parametrů, ve kterých bude zaručena efektivní funkce vzpěry ve VIS, konkrétně: časová odezva: 0-5ms, dynamický rozsah: 5-10. Před finálním návrhem vzpěry byla sestrojena vzpěra experimentální vzpěra, jejíž parametry byly přesně naměřeny a využity pro verifikaci jednotlivých modelů. Poznatky získané během experimentů byly využity při návrhu finální vzpěry. Jeden z nejdůležitějších poznatků byla nutnost náhrady feritového magnetického obvodu s ohledem na jeho křehkost. Proto byl odvozen tvarový přístup k navrhování rychlých magnetických obvodů z oceli s využitím 3D tisku, který byl následně patentován. Navržená vzpěra obsahuje magnetoreologický ventil jehož odezva je predikována na 1.2 ms a dynamický rozsah 10. V závěru práce je představena metodika, díky které byla vzpěra navržena.
128

Krytý městský bazén - betonová konstrukce nádrže / Indoor swimming pool - concrete tank construction

Pőthe, Péter January 2019 (has links)
The aim of the diploma thesis was to design reinforced concrete construction of the indoor swimming pool and ensure impermeability of the construction, to ensure behavior as concrete tank construction. Static analysis was done by using program Dlubal RFEM 5.12, where interaction of subsoil with construction was taken into account. Slabs around the swimming pool area were divided into expansion section because of temperature changes from glass façade an after that the sealing of expansion gap was solved. Construction system under the swimming was designed and was tested the behavior of walls and slabs. Analysis was done also to considerate of hydration heat. The drawing was done by software CADKON RCD.
129

Předpjatý komorový most / Prestressed box girder bridge

Štíchová, Kateřina Unknown Date (has links)
The subject of this diploma thesis is the design of a load–bearing structure, whitch is situated in the extravillain between the town of Chomutov and the village Křimov. Main purpose of this structure is to pass a roadway I/7 across the valley. There are three options of design and one of them – the prestressed box girder bridge with slanted walls is chosen for more detailed elaboration. The major load–bearing structure is five–span with lenghts 46.50 + 58.00 + 58.00 + 58.00 + 46.50 m, made of post–tensioned nad cast–in–place concrete. The total lenght of load–bearing structure is 269.00 m and the width of load–bearing structure is 13.50 m, the bridge is straight in plan. The structure is analyzed by several computational models, which are designed in Scia Engineer 20.0 software. The structure is analysed in longitudinal and cross directions. The assessments of load state limit and usability limit state are made according to valid standards. This thesis also included time dependent analysis (TDA), that takes construction stage analysis into account.
130

Dřevěná nosná konstrukce víceúčelové haly / Multipurpose load-bearing timber hall structure

Matuška, Martin January 2013 (has links)
This Master’s thesis is focused on the design and structural analysis of load-bearing structure of a multipurpose hall that is strained by the permanent load, working load and climatic load. The hall has the shape of an elliptical dome. Maximum margin of the structure is 60,0m and maximum height is 18,0m. Main carrier elements of the structure are radially arranged curved beams made of glued laminated timber, class SA(GL24).

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