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Form finding of shell structures
Musil, Jiří ; Bažant, Zdeněk (referee) ; Vítek,, Jan (referee) ; Stráský, Jiří (advisor)
The theme of this doctoral thesis is the design of concrete shell structures with the focus on finding their optimal shape. The optimal shape of a concrete shell is the shape in which for a given load (usually the dead weight of the structure) no significant bending moments are generated in the shell and the structure is in the so-called membrane state. The inspiration for this thesis is the work of Swiss engineer Heinz Isler, who developed the shapes of shell structures using model tests of appropriately loaded flexible membranes. He developed the shell structure for large spans by inverting the resultant shape, which carried its weight almost entirely via membrane forces. The numerical solution of the above experiments using Midas Civil is presented herein. The basic principles of the method are demonstrated on the example of sagged cable. The numerically found shapes are compared with the analytical solution. A shell is designed based on the numerically found shapes and its stress response to dead load is described, particularly in relation to the membrane action. In the next part, the acquired knowledge and methods were used to design three relatively complicated shell structures. Each structure was statically analysed and its static behaviour was described. Structures with perfectly rigid or flexible supports, which simulate real behaviour of the supports, were studied. In the final phase, the results of static analysis of the selected shell were experimentally verified on a physical model in a scale of 1: 55.56. The model has been built using 3D printing. The thesis describes the use of a modelling similarity, the model design, the production process, and the experiment. The load test confirmed the optimal design of the shell structure and the validity of the numerical method for finding their shapes.
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Motorway Viaduct
Polách, Marek ; Šopík,, Leonard (referee) ; Stráský, Jiří (advisor)
The thesis is a design of a bridge crossing the valley of the Hrabyňka creek as a part of road I/II. Firstly, three possible structures are designed and according to their advantages and disadvantages, the best of them is selected. In this case a cable stay bridge was selected. Following is a design of span lenghths, collumn heights and the cross-section. Then the loads are detremined and applied on a numeric model cretaed in software working on the basis of FEM. In continuation internal forces are calculated and their propriate combinations for service limit stay and ultimate limit state with time dependent analysis taken into account. In the end the reinforcement steel is designed for one part of the structure. Detailed drawings are also part of the thesis.
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Suspension footbridge across the Elbe River
Gregor, Petr ; Kocourek, Petr (referee) ; Stráský, Jiří (advisor)
The objective of this master´s thesis is a design of suspension footbridge across the Elbe river. The footbridge is suspended construction by three spans. The brick deck is supported on the outer edges and it is kept in a parabolic arc. The suspension cables are kept at two inclined levels. The model is implemented in the program ANSYS. The solution is non-linear. The designe is according to the europien standart.
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Analysis of a plan curved cable stayed and suspension footbridges
Koláček, Jan ; Stráský, Jiří (advisor)
The aim of the doctoral thesis focuses on the static and dynamic analysis of a plan curved cable stayed and suspension pedestrian bridges suspended on a single-side of their deck. The first part of this thesis deals with an analysis of the equilibrium in the transversal direction of a deck cross section suspended on a single-side. The section and its arrangement should be designed so that the torsion caused by the deck self-weight and dead load would be minimal. This theory was verified on a simple study of a single-sided suspended section with and without prestressing. Second part of the thesis deals with the design of a study of a plan curved cable stayed pedestrian bridge. The study describes in detail a finding of an initial state of the structure and the static and dynamic analysis performed by software ANSYS. The static analysis describes the response of the structure on the most frequent variable loads only, but not design of dimensioning according to the valid codes. The dynamic analysis verifies a predisposition of the structure to the vibrations and others harmful oscillation effects. The next objective of the thesis was to design a study of a plan curved suspension pedestrian bridge suspended on a single-side. A process of an analysis of these structures has not found in any available references. Especially, the finding of an initial state of a suspension cable has not been documented anywhere and by anybody. The study was analyzed with the same geometry as the cable stayed variation in order to compare both structures. The static and dynamic analysis was performed, too. The last part of the thesis describes the verification of structural solution on a fully functional model in a 1:10 scale, proposed process of the initial state finding, response of the structures on the loading and ultimate load test. The important step is the comparison of the results of the completed physical model and the calculation model.
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Stress ribbon curved structure
Kocourek, Petr ; Stráský, Jiří (advisor)
The theme of this doctoral thesis is research of footbridges curved in plan that are formed by stress ribbon. Recently, several noteworthy curved pedestrian bridges, which decks are suspended on their inner edges on suspension or stay cables, have been constructed. However, curved stress ribbon bridges have not been built so far. The goal of this study was to answer the question whether the use of curved stress ribbon structures is even possible. For this reason, in the first stage feasibility study of these structures has been prepared. Knowledge of both curved pedestrian bridges, which decks are suspended on their inner edge and straight stress ribbon has been used. For the mathematical modeling FEM software ANSYS was used. The obtained findings were further used to design a new type of a modern, aesthetic curved bridge for pedestrians. The structure is formed by slender reinforced deck, which is through the steel brackets on the inner side stiffened by steel section. Torsion of the deck, caused by curved structure and asymmetrical cross-section, is reduced by cable situated in the handrail. Footbridge span is 45 m, arc camber in plan is 10 m, free bridge width is 3 m. Described is a general structure effect, detail static and dynamic analysis was carried out. Designed structure including construction stages were experimentally verified on a fully physical functional 1:6 scale model. The thesis describes the model analogy used for the design of the model, its structural design and its implementation. The model was subjected to a series of load tests including the final ultimate strength test. Performed tests confirmed the good match of calculation with the reality, correctness of the design and high resistance of designed construction. Acquired results and experiences from design and realization of model form the basis for practical realization of studied structures.
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Footbridge formed by a stress ribbon and arch
Glajcar, Karel ; Novotný,, Petr (referee) ; Stráský, Jiří (advisor)
The subject of this master’s thesis is the design of footbridge across the river. The main objective is to analyse the superstructure which is formed by a stress ribbon and arch. The arch consists of two separate plan curved concrete arches and is associated with stress ribbon in the top. The analysis of the structure has been performed using MIDAS CIVIL 2011 software. Simplified calculations by hand or by EXCEL have been also carried out. Design of the superstructure's elements, pre-stressed tendons and reinforcement has been done according to EUROCODE. In the analysis, time dependent effects have been also taken into account.
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Plan curved arch footbridge
Trenz, Jan ; Romportl, Tomáš (referee) ; Stráský, Jiří (advisor)
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.
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Bridge across the motorway
Jetmar, Ondřej ; Jurík, Michal (referee) ; Stráský, Jiří (advisor)
The thesis deals with the design of a bridge structures panning the highway. While designing the structure, it was vital to consider and implement the needs for both the aesthetic and economical desires and requirements. Of the two design solutions in the thesis, the one of the three-spaninteg rated spandrel beam is chosen. The main goal is a thorough design of the a forementioned load bearing structure.
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Bridge across the Lochkov Valley
Zvolánek, Lukáš ; Juchelková, Pavlína (referee) ; Stráský, Jiří (advisor)
The theme of the Master’s thesis is detailed design of superstructure for selected option of the bridge. The bridge carries highway across Lochkov valley. The superstructure, 6 spans, is made of one cell continuous box beam with large overhangs supported by prefabricated struts. The continuous beam is in plan curvature. As the first, side spans 1, 5, 6 will be casting on fixed scaffolding. Spans 2 and 4 will be casting using cantilever method, gradually hanging superstructure up. For the casting the main span will also be using cantilever method, gradually removing temporary hangers of adjacent spans. The structure was analysed according to limit states. The thesis also includes a time dependent analysis of the structure and solution of influence construction on its design.
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Footbridge across the Berounka
Zlatuška, Karel ; Romportl, Tomáš (referee) ; Stráský, Jiří (advisor)
The diploma thesis deals with design of plan – curved footbridge over Berounka river near the town of Čivice. Three different options were developed. First option includes a single – beam prestressed integral construction with haunches. The second option includes suspension footbridge construction, where the bridge deck is suspended at one side. In the third option the main span is built from concrete segments. Those are suspended on a pair of steel arches. The access ramps are cast – in – place, and they are supported by round steel piers. This variant was finally chosen as the best one and it was further processed. The construction was analyzed with Scia Engineer 2015 software, considering the construction process. The footbridge was loaded with dead loads and live loads including traffic and thermal actions. The internal forces were calculated and the construction was assess to the serviceability and ultimate limit states. In terms of serviceability, stress in concrete sections and deformations were checked. In terms of the ultimate limit state, the ultimate load capacities were calculated. The steel arches and piers were checked for possibility of loss of stability by buckling. The loss of stability was also checked by the software. Finally the dynamic behaviour of the construction was assessed, especially the harmonic excitation response. Then the construction plan and the drawings were made. The drawings include overview drawings and detailed drawings.
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