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Optimization of prestress tendon path
Středulová, Monika ; Lehký, David (referee) ; Eliáš, Jan (advisor)
The thesis explores possibilities of applying genetic algorithms on the problem of finding the optimal prestressed concrete tendon path. The objective of the thesis is to develop a genetic algorithm based on the Automatic Dynamic Penalization method and to test its robustness on selected analytical functions. Subsequently, the algorithm is connected to a Time Dependent Analysis module for the computation of prestressed concrete structure to solve selected examples of prestressed beams in the form of a constrained optimization problem. The algorithm is developed in the Python programming language with the help of the Distributed Evolutionary Algorithm library.
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Probabilistic analysis of reinforced concrete bridge made of I-73 girders
Nezval, Michal ; Šomodíková, Martina (referee) ; Lehký, David (advisor)
Many older bridges on the highways and roads in the Czech republic and all arend the world have been designed by codes, which are distinct of currently valid codes. Considering current codes, it is possible to set load bearing capacity in few different ways. In presented diploma thesis nonlinear finite element analysis using deterministic methods is compared with fully probabilistic nonlinear finite element analysis. Girder I-73 is analysed. Also the influence of degradation processes and following corrosion of reinforcement is taken into account, when load capacity is predicted for residual service life.
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Evaluation of fracture tests of selected concrete specimens
Součková, Markéta ; Lehký, David (referee) ; Keršner, Zbyněk (advisor)
This bachelor thesis deals with evaluation of fracture tests of selected concrete specimens. It is divided into two parts: theoretical and practical. The theoretical section describes fracture parameters, three point bending test and effective crack model. It explains evaluation process of the expriments step by step, too. The practical part contains charts with the resulting values of fracture parameters. The StiCrack software was used for analysis of fracture tests. The result of this thesis is comparison of influence the thength classes of concrete, age of specimens and place of ripen on the values of fracture parameters.
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Probabilistic reliability and durability analyses of reinforced concrete bridges
Šomodíková, Martina ; Kohoutková,, Alena (referee) ; Sýkora,, Miroslav (referee) ; Lehký, David (advisor)
This thesis deals with the development of a complex methodology for probabilistic analysis of reliability and durability of reinforced concrete structures, especially road bridges. An estimation of load-bearing capacity is carried out using probabilistic methods in combination with the nonlinear finite element method analysis and also with respect to reliability requirements according to standards. The current state of the structure is taken into account based on the mathematical modeling of the degradation processes, such as concrete carbonation, chloride ingress and subsequent corrosion of reinforcement. Then the load-bearing capacity and reliability is predicted over time. Attention is focused on the upgrade of the analytical models for modeling of degradation processes with regard to the effect of mechanical load on the structure or its components, the development of an artificial neural network-based response surface method for efficient approximation of the original limit state function with respect to the accuracy and a minimization the number of simulations, and an interconnection of individual processes and advanced methods in an automatic process.
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Inverse reliability analysis of prestressed bridge
Lipowczan, Martin ; Novák, Drahomír (referee) ; Lehký, David (advisor)
The proposed diploma thesis deals with the application of methodology and tools of inverse analysis for design of selected structural parameters using a fully probabilistic analysis to determine the level of its reliability. The method based on artificial neural networks is used to approximate the inverse function. The inverse analysis was carried out in two ways that differs in the method of obtaining reliability indicators. The structure analyzed in this work was an existing bridge. The year of construction is estimated approximately between the years 1955 to 1960. The bridge is located close to the Uherský Ostroh. It is a one-piece concrete slab made of MPD3 and MPD4 girders post-tensioned by tendons. Based on the 2006 and 2007 diagnostic surveys, laboratory tests, normative regulations and recommendations and, last but not least, sensitivity analyses, an inverse design of selected design parameters was performed for required limit states. Various load levels, different alternatives of design parameters and different neural network structures were studied.
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Life-time assessment of bridge based on nonlinear analysis and degradation modelling
Kucek, Martin ; Lehký, David (referee) ; Novák, Drahomír (advisor)
The aim of this work is to calculate the lifetime period of the bridge construction based on the nonlinear analysis and the degradation modelling. As a solution was the probabilistic nonlinear finite element analysis. The nonlinear numerical analysis is provided by the programme ATENA, developed by the Červenka Consulting. We have modeled one prefabricated bridge beam KA-73, which was overloaded by power effects until the structure was damaged. Observed limit states, limit state of the decompression, crack formation and limit state of the bearing were compared with characteristic material. It is possible to determine the maximum weighted capacity for the given construction based on discovered values.
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Advanced simulation methods for reliability analysis of structures
Gerasimov, Aleksei ; Lehký, David (referee) ; Vořechovský, Miroslav (advisor)
The thesis apply to reliability problems approach of Voronoi tessellation, typically used in the field of samples designs evaluation and for Monte Carlo samples reweighing. It is shown, this general technique estimation converges to that of Importance Sampling method despite it does not rely on Importance Sampling's auxiliary density. Consequently, reliability analysis could be divided into sampling itself and assessment of simulation results. As an extension of this idea, adaptive statistical sampling using QHull library was attempted.
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Comparison of reliability methods in determining the design resistance of a bridge
Šplíchal, Bohumil ; Doležel, Jiří (referee) ; Lehký, David (advisor)
This thesis deals with the topic of assessing the design load-bearing capacity of a prestressed concrete railway bridge structure. The determination of the structure’s load-bearing capacity is carried out using probabilistic nonlinear analysis using the finite element method. Load-bearing capacity is determined for the recommended limit states. A fully probabilistic approach is compared to other reliability semi-probabilistic methods, such as the ECoV method according to Červenka and Eigen ECoV, and deterministic methods, like partial safety factor method, or the method according to ČSN EN 1992-2. The results are evaluated in terms of accuracy, consistency and time consumption for each method.
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Comparison of reliability methods in determining the design resistance of a bridge
Šplíchal, Bohumil ; Doležel, Jiří (referee) ; Lehký, David (advisor)
This thesis deals with the topic of assessing the design load-bearing capacity of a prestressed concrete railway bridge structure. The determination of the structure’s load-bearing capacity is carried out using probabilistic nonlinear analysis using the finite element method. Load-bearing capacity is determined for the recommended limit states. A fully probabilistic approach is compared to other reliability semi-probabilistic methods, such as the ECoV method according to Červenka and Eigen ECoV, and deterministic methods, like partial safety factor method, or the method according to ČSN EN 1992-2. The results are evaluated in terms of accuracy, consistency and time consumption for each method.
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Multilevel Determination of Mechanical Fracture Parameters of Concrete from Wedge Splitting Tests
Lipowczan, Martin ; Šomodíková, Martina ; Lehký, David
The paper presents the results of a part of the research focused on the development of a complex experimental–computational methodology for determining the values of mechanical fracture parameters of concrete independent of the specimen size and geometry. For this purpose, laboratory wedge splitting tests were carried out on specimens of three different sizes with two different notch depths. Based on the experimentally obtained responses of the test specimens, the fracture mechanical parameters of all specimens were identified by inverse analysis. The obtained parameters were used in the numerical simulation of the tests and analysed in terms of their dependence on the size of the initial uncracked ligament.
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