|
|
Numerical analysis of visco-elastic material models
Michálková, Veronika ; Lang, Rostislav (referee) ; Trcala, Miroslav (advisor)
The serviceability of concrete structures is a multiphysical problem where viscoelasticity is interrelated with plasticity or damage, among other things. This work focuses on the analysis and testing of an isotropic viscoelastic material model based on a generalized Kelvin chain. The Kelvin chain is described in detail for 1D strain and then its application to multi-axial 2D plane strain is shown. In this paper, a total of 3 studies are carried out using the Kelvin chain. The first study concerns the analysis of the Kelvin chain with damage on several benchmark refinement problems. The second study compares the results of the Kelvin chain including damage with an experiment on a three-point beam bending problem. The third study concerns the analysis of the Kelvin chain with damage on a stress relaxation problem in a loaded concrete beam and compares the results with the ANSYS calculation and experimental measurements. The aim is to analyze the effect of the parameter on the time-dependent behavior of the concrete and also the effect of the number of time increments N on the result.
|
|
|
Design and analysis of membrane roof of a stadium.
Lang, Rostislav ; Kytýr,, Jií (referee) ; Němec, Ivan (advisor)
This diploma thesis deals with problem of design and calculation of membrane structure of stadium roof. This is a complex engineering problem, which includes many partial problems: finding of initial form of membrane, statically and architecturally suitable arrangement of catenaries, economical solution of boundary conditions (foundations). All components affect each other and cannot be dealt without mutual coordination. It always greatly depends on the experience and intuition of engineer who design such structure. Task which cannot be resolved according to the theory of the first order. Equilibrium forces on the deformed structure, which in many projected structures gives satisfactory results, did not correspond to reality. It is therefore necessary to consider equilibrium of forces on the deformed structure according to the theory of large deformations. Diploma thesis was entered with regard to the intention of the companies Ing. Software Dlubal s.r.o. and FEM consulting s.r.o., working together to develop software RFEM. These companies plan to complement this program system with a module MEMBRANE for searching of initial shapes of membrane structures. This work is a contribution to the creation of this module.
|
|
|
Analysis of membrane structures
Motyčka, Tomáš ; Zajac, Zbyněk (referee) ; Lang, Rostislav (advisor)
This thesis focuses on a comprehensive analysis and design of membrane structures that are one of the most dynamically developing areas in structural engineering. These structures, that are characterised by their ability to cover large spans with a minimum number of supporting elements and provide high levels of natural light due to their translucency, are examined in this thesis from theoretical and practical perspectives. In the theoretical part of the thesis, the basic principles of their design and analysis are described, including detailed A detailed discussion of the materials and technologies used. Special attention is paid to mechanical properties of fabrics, which are crucial for the functionality and durability of these structures. The second chapter deals with the numerical analysis of membrane structures, with an emphasis on the non linear mechanics, the form-finding process for determining the optimal shape of the structure, and methods for calculation of cutting patterns. In the practical part, case studies are presented, including the analysis of prestressed membrane of the Anthropos dance pavilion and the ETFE cushion roof structure. These studies offer insights into the challenges and solutions associated with the design and analysis of membrane structures, including detailed descriptions of the structures, calculation models and load analyses. Specific emphasis is placed on Analysis of the 'ponding' effect, a common cause of failure in these structures.
|
|
|
The influence of the magnitude of normal forces on nonlinear seismic analysis
Holiš, Ondřej ; Lang, Rostislav (referee) ; Vlk, Zbyněk (advisor)
The thesis is focused on studying the influence of the magnitude of normal forces and loads on the nonlinear dynamic analysis. Pushover method and nonlinear time history analysis were used to solve these problems. A number of numerical models with different nonlinearities and progressively increasing loads have been developed. The results were then compiled into graphs and tables for comparison. RFEM 5, RFEM 6 and a program in Python were used for the calculations.
|
|
|
Algorithms for design and analysis of membrane structures
Lang, Rostislav ; Krejsa,, Martin (referee) ; Kytýr, Jiří (referee) ; Němec, Ivan (advisor)
Předkládaná práce se zabývá problematikou navrhování membránových konstrukcí, a to především s ohledem na vývoj potřebných výpočetních nástrojů v rámci MKP programů. Po uvedení základních fyzikálních požadavků jednotlivých kroků při navrhování těchto konstrukcí budou dále prezentovány vybrané či navržené algoritmy. Kapitola form finding se zabývá analýzou tvaru membránových konstrukcí. Rovnovážný tvar je odvozen od požadavku na výsledné předpětí, specifikované okrajové podmínky a aplikované zatížení. Obecně se ale tento proces zabývá i samotným hledáním rovnovážné soustavy sil v prostoru. V důsledku této skutečnosti jsou součástí popisované analýzy také vhodné stabilizační metody. V této kapitole budou prezentovány jak zvolené postupy, tak i navržená stabilizační technika specializovaná na hledání tvarů kuželových membrán. Dále je také popsán navržený algoritmus pro řešení úloh optimalizujících tvary ohybově tuhých konstrukcí, které jsou spjaty s hledáním labilních rovnovážných konfigurací. Kapitola structural analysis je zaměřená především na fenomén vrásnění membrán. Tato náhlá ztráta stability silně ovlivňuje statickou i dynamickou odezvu membránových konstrukcí. V rámci této kapitoly je představena a verifikována navržená výpočetní metoda, modulárně aplikovatelná na lineární, nelineárně elastické i plastické materiály používané pro uvedené konstrukce. Kapitola cutting pattern generation se zabývá výpočtem střihových vzorů, nezbytných pro výrobní proces membránových konstrukcí. Pro tento proces je v rámci předkládané práce navržena kombinace dvou různých metod. Zvolená posloupnost algoritmů cílí na optimalizaci poměru rychlosti, obecnosti a přesnosti výpočtu. Zmíněné kapitoly jsou doplněny jednotlivými příklady, analyzovanými pomocí popisovaných algoritmů, které demonstrují konkrétní fyzikální problémy či nezbytné implementační procesy.
|
|
| |
|
|
Analysis of membrane structures with respect to construction stages
Zajac, Zbyněk ; Kytýr, Jiří (referee) ; Lang, Rostislav (advisor)
This diploma thesis deals with problem of design and calculation of membrane structure. Design proces of light and airy structure was demonstrated on conical shaped roof in the finite element analysis program RFEM. The structure was loaded in the virtual wind tunnel in the program RWIND. Results were compared with the values given in the literature. A comprehensive guide for the design of membrane structures has been created. Subsequently, the influence of design stages on the internal forces was demonstrated. Membrane structures are very sensitive to construction stages, because it is not possible to prestress all membrane surfaces at once. Program by DLUBAL software s.r.o. was used for form-finding analysis during construction stages.
|
|
|
Particle swarm algorithm in problems of structural optimization
Šubíková, Magdaléna ; Lang, Rostislav (referee) ; Hokeš, Filip (advisor)
The thesis deals with the application of the nature-inspired stochastic particle swarm algorithm to the structural optimization problem in the Dlubal RFEM computing system. A sensitivity analysis of input parameters and optimization using PSOA was performed on a parametric member model of the steel structure of the Holedná tower. The main contribution of this thesis lies in the analysis of a specific algorithm configuration and its ability to effectively find the global minimum of the chosen objective function.
|
|
| |
|
| |
guest ::
RSS feed.