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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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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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Problems of Reliability of Steel Members Sensitive to Imperfections
Nezbedová, Anna ; Lehký, David (referee) ; Kala, Zdeněk (advisor)
This thesis deals with the problems of reliability of steel members sensitive to imperfections. Formulas for nonlinear analysis of compressed and bended members are derived. For compressed elements, there is described the issue of buckling, for bended elements it is lateral-torsional buckling. Then a statistical analysis of reliability of these problems is performed and also comparison with the approach described in Eurocode 3.
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Modelling of damping devices in interaction with a structure
Kalina, Martin ; Lehký, David (referee) ; Frantík, Petr (advisor)
The aim of my master’s thesis was to create models of the damping device and observing their behavior in interaction with the structure. First was the construction separately modeled with Java application named FyDiK2D like a model with one degree of freedom. Model of construction takes form like a high, thin rod with full circular cross section. The lower part was restrained into the subsoil. The design was to verify the correct functionality of the model by comparing the analytical and numerical solutions. For capturing the precise behavior of the structure was converted to a multi-stage model. Then the pendulum damper was applied on this construction and found amplitude lies in highest point of multi-stage model. He was then replaced by tuned mass damper. By comparing these amplitudes from both dampers was found which kind of damper is efficient for multi-stage model.
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Nonlinear analysis of load-bearing capacity of reinforced concrete bridge
Sadílková Šomodíková, Martina ; Novák,, Drahomír (referee) ; Lehký, David (advisor)
The subject of master’s thesis is determination of bridge load-bearing capacity and fully probabilistic approach to reliability assessment. It includes a nonlinear analysis of the specific bridge load-bearing capacity in compliance with co-existing Standards and its stochastic and sensitivity analysis. In connection with durability limit states of reinforced concrete structures, the influence of carbonation and the corrosion of reinforcement on the structure’s reliability is also mentioned.
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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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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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An efficiency comparison of simulation methods for artificial neural network training and inverse analysis
Nezval, Michal ; Novák, Drahomír (referee) ; Lehký, David (advisor)
The thesis deals with inverse analysis which is based on combination of artificial neural network and stochastic methods. The goal is to compare an efficiency of new simulation method Hierarchical Subset Latin Hypercube Sampling to classical Monte Carlo method and standard Latin Hypercube Sampling method used for neural network training. The efficiency is compared for a different neural network structures. The inverse analysis is then applied for engineering tasks – identification of limit state fiction parameters related to pitched-roof frame and material parameters of concrete specimen subjected to three-point bending. Finally an efficiency of Hierarchical Subset Latin Hypercube method comparing to Monte Carlo and Latin Hypercube Sampling methods is discussed.
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Utilization of inverse reliability analysis tools for probability based design of selected structural parameters
Lipowczan, Martin ; Novák, Drahomír (referee) ; Lehký, David (advisor)
This bachelor thesis deals with the application of methodology and tools of inverse analysis in regards to probabilistic design of selected design parameters of structure. The first step was to get familiar with the probabilistic design and analysis, then understanding of the inverse analysis methodology itself which is based on artificial neural networks. After researching the topic we could get to the actual issue. To put the theory in practice easier examples were used at first. These were mathematical functions and one practical-based example, whereas the results were known in advance. This simplified a process of checking achieved values. Using software tools and especially DLNNET software allowed us to take on practical exercises. Used exercises are chosen from earlier undergraduate studies at the Faculty of Civil Engineering, Brno. The first of these was a design of reinforced concrete slab, where desired parameters were slab’s height and area of reinforcement. The second one was a design of a diagonal truss screw connection, aimed to size the screw diameter and its quantity.
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