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Application of kriging in engineering problems with uncertainties
Tvrzník, Jakub ; Lehký, David (referee) ; Vořechovský, Miroslav (advisor)
The presented bachelor thesis aims at interpolation method called kriging, which is based on regression of values measured in the surroundings. Kriging is based on the idea that interpolated function is one realization of a random field. Using this method we can quantify the estimates of functional values at the surrounding points, including estimation errors at each point. At the same tame, kriging respects the exact measured values and the interpolation passes through them. The practical part demonstrates the application of method to engineering tasks, where the measured values are distributed randomly. In other examples, the measured values are distributed by using a grid.
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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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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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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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Probabilistic discrete model of concrete fracturing
Kaděrová, Jana ; Lehký, David (referee) ; Konečný,, Petr (referee) ; Eliáš, Jan (advisor)
The thesis presents results of a numerical study on the performance of 3D discrete meso–scale lattice–particle model of concrete. The existing model was extended by introducing the spatial variability of chosen material parameter in form of random field. An experimental data from bending tests on notched and unnotched beams was exploited for the identification of model parameters as well as for the subsequent validation of its performance. With the basic and the extended randomized version of the model, numerical simulations were calculated so that the influence of the rate of fluctuation of the random field (governed by the correlation length) could be observed. The final part of the thesis describes the region in the beam active during the test in which the most of the fracture energy is released in terms of its size and shape. This region defines the strength of the whole member and as shown in the thesis, it does not have a constant size but it is influenced by the geometrical setup and the correlation length of the random field.
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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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Determination of design resistance of reinforced concrete bridge
Šplíchal, Bohumil ; Doležel, Jiří (referee) ; Lehký, David (advisor)
This thesis deals with the topic of assessing the design load-bearing capacity of a reinforced concrete bridge structure. The determination of the load-bearing capacity of the structure is carried out by means of probabilistic nonlinear analysis using finite element method. Load-bearing capacity is determined for the recommended limit states. A fully probabilistic approach is compared to other recommended reliability methods, such as the ECoV method according to fib Model Code 2010, the partial safety factor method, or the method according to ČSN EN 1992–2. The results are evaluated in terms of accuracy and time-consuming for each method.
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Study of influence of input parameters for the numerical modeling of the compression test
Polách, Marek ; Keršner, Zbyněk (referee) ; Lehký, David (advisor)
The thesis analyses influence of input parametres of the 3D Non Linear Cementitious 2 material model for the numerical modeling of compression test performed in ATENA 2D and ATENA 3D software. The aim is to identify parametres with considerable influence and subsequently replicate the load-deflection curve obtained from laboratory compression test by numerical modeling. The effects of selected model and material model settings are studied on three kind of models in total. As tools for analyzing the effects, deterministic and statistic sensitivity analyses were chosen. Parametres with significant influence will be highlighted and added to the group of parametres obtained from numerical modeling of three-point bending test. This will create a set of parametres of considerable influence when it comes to modeling advanced structures with different types of stresses.
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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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