|
|
Stability problems study of framed structures
Piják, Jiří ; Vlk, Zbyněk (referee) ; Zídek, Rostislav (advisor)
In the first chapter the problem of ideal member, member with initial curvature and meaning of Euler’s critical force is regarded. Parameters of stability, mainly calculation of critical loading and buckling lengths, are studied in the second part. The same part contains comparison of results of computational programs and mechanical approach. Next attention is paid to imperfections, to possibilities of determination and comparison of results on a simple member. Comparison of possible judgements of buckling on a simple beam and on frames according to ČSN EN 1993-1-1 is performed on the final part.
|
|
|
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.
|
|
|
Study of Precision of the Stability Analysis
Sotulář, Jiří ; Pilgr, Milan (referee) ; Hron, Lukáš (advisor)
The thesis deals with the precision of the stability analysis of the pressed member. The loss of stability of the bukling is determinate by using several metods, which are compared each other. The thesis is partitioned into three parts that works together. The first part deals with the theory of analysis of the buckling stability. Here is described the gradual solution of analytical analysis for real beam and here is described the final compared for ideal, imperfekt and real beam too. It is also short solved buckling by using software. In the second part is compared by using computing systems and anylitical analysis for several basic buckling systems. The results of the compared are summarised in the final graphs and tables for each solved element and systems. In the third part are designed and static checked load-bearing element of steel storage hall. The buckling beams are checked by using findings from the previous analysis.
|
|
|
Continuous welded rail in tight curves
Peřinová, Kateřina ; Szabó, Petr (referee) ; Plášek, Otto (advisor)
The diploma thesis deals with the curve radius influence on lateral stability of continuous welded rail. It is presented the overview of present state of knowledge in the field of stability of continuous welded rail. In practical part is created the model of a track section. The influence of some parameters on loss of stability of CWR was studied. The results it are compare with the analytic analysis.
|
|
|
Stabilitní analýza ocelových konstrukcí s imperfekcemi
Kalina, Martin ; Krejsa, Martin (referee) ; Kala, Jiří (referee) ; Kala, Zdeněk (advisor)
The aim of this work is focused on soluti0on stability problem of planar bar structures. The calculation algorithms and methods used for analysis of behavior of these structures are described. The discrete computational model of steel of von Mises planar truss is presented. The structure deformation is evaluated by seeking the minimal potential energy. The effect of vertical displacement of top joint is determined by step-by-step method, and Newton iteration. Symmetric and asymmetric effects of initial shape of geometric imperfections of axes of struts are used in the model. The work is focused on another step in research of mapping of potential energy of elastic structures with aim at arch structures. For selected hinged arch loaded by displacement in the midpoint, the area of two concurrently existing postcritical statical equilibrium states is scanned using dynamical relaxation and applying of a set of designed mapping methods.
|
|
|
Lateral-torsional buckling of beams - analysis of specific cases
Piják, Jiří ; Barnat, Jan (referee) ; Bajer, Miroslav (advisor)
Thesis deals with flexural-lateral buckling of asymmetric cross sections, especially assessment according to ČSN EN 1993-1-1. Models are based on bar, shell and solid finite element method. Assessment of software Scia Engineer and RFEM are analysed in bar model. Plate and volume model uses shell and solid elements and initial imperfections. Computing is geometrically nonlinear. Correspondence of bar and plate model is studied. Optimal amplitude is suggested. Simple beam loaded with continuous line loading is taken as an example.
|
|
| |
|
|
Continuous welded rail in tight curves
Peřinová, Kateřina ; Szabó, Petr (referee) ; Plášek, Otto (advisor)
The diploma thesis deals with the curve radius influence on lateral stability of continuous welded rail. It is presented the overview of present state of knowledge in the field of stability of continuous welded rail. In practical part is created the model of a track section. The influence of some parameters on loss of stability of CWR was studied. The results it are compare with the analytic analysis.
|
|
|
Lateral-torsional buckling of beams - analysis of specific cases
Piják, Jiří ; Barnat, Jan (referee) ; Bajer, Miroslav (advisor)
Thesis deals with flexural-lateral buckling of asymmetric cross sections, especially assessment according to ČSN EN 1993-1-1. Models are based on bar, shell and solid finite element method. Assessment of software Scia Engineer and RFEM are analysed in bar model. Plate and volume model uses shell and solid elements and initial imperfections. Computing is geometrically nonlinear. Correspondence of bar and plate model is studied. Optimal amplitude is suggested. Simple beam loaded with continuous line loading is taken as an example.
|
|
|
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.
|
guest ::
