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Material nonlinear solution of beam structures
Kabeláč, Jaromír ; Krejsa,, Martin (referee) ; Návrat,, Tomáš (referee) ; Němec, Ivan (advisor)
The dissertation deals with solution of beam and frame structure considering material nonlinearity. The finite elements method (FEM) was used as calculation method. The objective of the dissertation was to develop and test finite beam element considering material nonlinearity. A detailed analysis of the problem provided a group of formulations of beam element. Part of the dissertation´s results has been, in several forms, implemented in commercial software. Beam element focused on solution of stress over solid cross sections is introduced in the theoretical part. In terms of topology it is a classical prismatic beam element with two nodes. Six degrees of freedom for translations and rotations are defined in each node plus 7-th degree of freedom for warping function from torsion. Load form axial force, bending moments, primary torsion, shear forces and eventually bimoment for secondary torsion were considered in cross section. Several variants of formulations were created according to inclusion of loading components into material nonlinearity and according to numeric integration method. Inclusion of geometric nonlinearity and fire resistance calculation are discussed in the dissertation. The above mentioned formulations were tested on prototypes as described in the application part which also provides information on the general procedure, architecture and technologies used for implementation of knowledge from the theoretical part into commercial FEM software. The dissertation shows implementation of plasticity for shell, solutions of cross section characteristics and stress on cross section, implementation of beam element with material nonlinearity and module for fire resistance of column. The above mentioned implementations of theoretical conclusions are the main outputs of the dissertation. These implementations are available in thousands of installations throughout Europe where being used at projection of significant constructions.
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Floor detection during elevator ride
Havelka, Martin ; Králík, Jan (referee) ; Krejsa, Jiří (advisor)
This diploma thesis deals with the detection of the current floor during elevator ride. This functionality is necessary for robot to move in multi-floor building. For this task, a fusion of accelerometric data during the ride of the elevator and image data obtained from the information display inside the elevator cabin is used. The research describes the already implemented solutions, data fusion methods and image classification options. Based on this part, suitable approaches for solving the problem were proposed. First, datasets from different types of elevator cabins were obtained. An algorithm for working with data from the accelerometric sensor was developed. A convolutional neural network, which was used to classify image data from displays, was selected and trained. Subsequently, the data fusion method was implemented. The individual parts were tested and evaluated. Based on their evaluation, integration into one functional system was performed. System was successfully verified and tested. Result of detection during the ride in different elevators was 97%.
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Reliability Analysis of Steel Columns with Encased Web in High Strength Concrete under Compression
Puklický, Libor ; Krejsa,, Martin (referee) ; Melcher, Jindřich (referee) ; Kala, Zdeněk (advisor)
The presented paper deals with a theoretical analysis of the ultimate limit state. The results of experimental research carried out at the Institute of Metal and Timber Structures headed by Assoc. Prof. Karmazinová and Professor Melcher were applied. The geometrically and materially nonlinear solution based on the Timošenko’s solution is verified by the FEM model in the computer programme system ANSYS. The random influence of initial imperfections is taken into consideration. The FEM model also includes the influence of residual stress. In the parametric study, the influence of residual stress on the cross-section plastification is researched into, its influence on the load carrying capacity limit is, together with the influence of other imperfections, the subject of the stochastic analysis, applying the Latin Hypercube Sampling (LHS). Further on, the study proves a direct effect of the concrete part of the cross-section (combination of materials steel-concrete) on the decrease of load carrying capacity limit of the beam caused by influence of the residual stress of steel. With regard to the importance of time dependent phenomena of the concrete creep for the load carrying capacity, the studies given in the Ph.D. thesis are oriented in this respect. The parametric studies of the influence of the concrete creep having applied the Standard Eurocode 2 provide both a comparison of load carrying capacity limits when using common and high-strength concrete types, and also the variability of load carrying capacities. It follows from the comparison of the statistical analysis outputs according to the design reliability conditions of the Standard EN1990 and of the approach of Eurocode 4 that the Eurocode 4 can be recommended for dimensioning of this member type. According to the studies which we carried out, the design in compliance with Eurocode 4 can be evaluated as the reliable one. A larger set of experimental data is necessary to determine the economy.
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Automatic detection of elevator controls using image processing
Černil, Martin ; Šnajder, Jan (referee) ; Krejsa, Jiří (advisor)
This thesis deals with the automatic detection of elevator controls in personal elevators through digital imaging using computer vision. The theoretical part of the thesis goes through methods of image processing with regards to object detection in image and research of previous solutions. This leads to investigation into the field of convolutional neural networks. The practical part covers the creation of elevator controls image dataset, selection, training and evaluation of the used models and the implementation of a robust algorithm utilizing the detection of elevator controls. The conclussion of the work discusses the suitability of the detection on given task.
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Development of methods for analysys road safety barriers in terms of dynamic effects
Koudelka, Ivan ; Krejsa,, Martin (referee) ; prof. Ing. Alois Materna, CSc., MBA (referee) ; Salajka, Vlastislav (advisor)
The presented work analyses the methodology and approach of the legislation. It presents in the press presented results of numerical modelling of the impact of vehicles crashed into barriers that are being solved in the Czech Republic and worldwide. It presents a recommendation of a methodology for assessing crash barriers. The methodology follows the basic principles used in the TP 101 and EN 1991-1-1. The kinetic energy of the vehicle at the moment of impact is replaced with substitute static force, whose effects are comparable with those of a vehicle collision. The supporting structure of crash barriers is implemented in compliance with means of statics. The calculation includes the vehicle deformation, which represents the real distribution of the energy absorbed by the deformation of the vehicle and the energy that crash barriers need to absorb. The proposed methods allow to take into account non-linear behaviour of the structure both in terms of geometry and in terms of material nonlinearity. The work also deals with the interpretation of various types of support structures in the computational model. A specific case is used for a demonstration of a way of modelling the elastic supporting column of crash barriers in the soil, or modelling the friction of a loose concrete block over the surface. To ensure the proper position of interconnected loose blocks corresponding to the reality, a method of modelling the place of a possible contact of the breakthrough is drafted. A significant contribution to the more accurate calculation is achieved by sequential increase of the load on the construction by using load increment and measurement of energy increases absorbed by the deformation in each step. The presented methodology is an effective tool to assess crash barriers. For the application of this tool, using common resources and facilities available to almost every designer dealing with statics of structures is sufficient. In conclusion, the knowledge obtained fr
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Design of docking station for mobile robot
Obšil, Tomáš ; Houfek, Martin (referee) ; Krejsa, Jiří (advisor)
The aim of this diploma thesis is design of docking station for an autonomous mobile robot Breach. The task of docking station is to connect this robotic device to power supply without human intervention in order to charge its batteries. The theoretical part of diploma thesis contains research study about autonomous charging of robots. After that it is assessed suitability of using different types of docking stations and it was chosen optimal solution. The practice part of diploma thesis contains design of docking mechanism, which takes account of inaccurate navigation of robot with deviation of several centimeters. One part of this design deals with connector system, which is dimensioned for long-term transmission of electric current with minimal value of 20 A. At the end of diploma thesis there was created 3D model of the complete docking station including connectors for charging in program called SolidWorks.
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Vehicle speed estimation
Roštek, Martin ; Kumpán, Pavel (referee) ; Krejsa, Jiří (advisor)
Rýchlosť vozidla je jednou z kľúčových stavových premenných, ktorej znalosť je potrebná v reálnom čase a s vysokou presnosťou, aby mohla slúžiť ako vstupná veličina pre systémy kontroly dynamiky vozidla. Jej priame meranie vo vozidle je však finančne náročné. Riešením tohoto problému môže byť použitie meraní zo senzorov bežne dostupných na palube vozidla a ich následný prepočet na rýchlosť vozidla. Tieto merania sú však veľmi zaťažené procesným šumom, čo vyplýva z komplexnosti pohybu vozidla. Preto je nutné vyvinúť algoritmus so schopnosťou vysporiadať sa s týmito negatívnymi vplyvmi. Algoritmus prezentovaný v tejto práci odhaduje pozdĺžnu rýchlosť vozidla s použitím meraní uhlových rýchlostí štyroch kolies, pozdĺžnej akcelerácie, momentov motora, rýchlosti otáčania okolo zvislej osi a natočenia volantu. Algoritmus bol testovaný na veľkom počte situácií považovaných za kritické na odhad rýchlosti vozidla, ako napríklad prudká akcelerácia na vozovke s nízkym koeficientom trenia, núdzové brzdenie s aktiváciou ABS, či jazda v kopci s kolesami v preklze, prinášajúc uspokojujúce výsledky.
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