1. CALIBRATION OF A NEW METHOD FOR CREATING IMPERFECTIONS ON SLENDER STRUCTURES : magistrsko deloSimon Hudales, 2022, magistrsko delo Opis: For the design of slender structures consisting of plates and tubes, such as supporting structures at cranes, buckling is beside stress and fatigue often the governing failure criteria. Stability analysis of such structures is usually performed using the GMNIA method according to DIN EN 1993. For this purpose, a suitable geometric equivalent imperfection must be applied to the structure. Buckling inherent shapes are determined for this purpose and scaled according to applicable safety concepts. Including imperfections in stability analysis can generally be relevant for the load-bearing behavior of a structure. Within this master thesis work, the influence of the initial geometric imperfection on stability behaviour is investigated.
This study examines the influence, that imperfections imposed on members subjected to tensile stress have on stability behaviour. Tensile members of structures are identified and initial geometric imperfection is imposed on them in addition to critical members, that are subjected to compression stress. It is shown, that including imperfections on tensile members in stability analysis, has only a minor influence on stability behaviour and stiffness of the structure, both reducing it just slightly.
Further on, investigation on boom model, that is supporting structure of the crawler crane, is made. Boom model consist of main chord members and diagonals connecting them. At the joint connection of boom and two diagonal members, one subjected to tension and one subjected to compression stress, appears area of high shear stresses. Influence of the direction, that imperfection is imposed on the diagonal member, and what is the influence on the stability behaviour and structural strength is presented in this work. Most severe case of the two chosen direction is pointed out and discussed. Ključne besede: stability analysis, initial geometric imperfections, thin-walled structures, finite element method Objavljeno v DKUM: 06.07.2022; Ogledov: 250; Prenosov: 42 Celotno besedilo (5,14 MB) |
2. Non-linear finite-element modelling of room and pillar mine workings including the strain-softening behaviour of the rock massSalim Bensehamdi, Abdelbaki Seriani, 2008, izvirni znanstveni članek Opis: A two-dimensional model adopting post-failure criteria was used to simulate the behaviour of the rock mass and the development of yield zones around room and pillar mine workings. The model conformed to the strain-softening behaviour of the rock mass and accounted for its post-failure residual strength. The structural-stability-analysis approach accounted for the main features of the mine structures’ yield produced during loading through changes in the rock material’s stiffness and the subsequent evolution of the stresses. A comprehensive parametric analysis was performed and the inevitable effect of the interaction of the roof, pillar and floor on the overall stability limit of the mine was investigated. The numerical results clearly showed that the finite-element linear models could not realistically represent the true behaviour of the mine structure. However, they clearly demonstrated the limitations of the finite-element linear solutions in representing the true behaviour of the mine structure, particularly when the rock-mass structure is relatively weak, and that a non-linear approach was justified. Ključne besede: non-linear FE analysis, yielding, plastic zones, room and pillar mining, residual strength, stability assessment Objavljeno v DKUM: 05.06.2018; Ogledov: 811; Prenosov: 68 Celotno besedilo (651,93 KB) Gradivo ima več datotek! Več... |
3. A 3D nonlinear dynamic analysis of a rock-fill dam based on IZIIS softwareVioleta Mircevska, Vladimir Bickovski, Mihail Garevski, 2007, izvirni znanstveni članek Opis: This paper treats the 3D nonlinear dynamic behavior of a rock-fill dam based on the Mohr-Coulomb failure criterion. The dam is situated in a steep, narrow, “V-shaped” rigid canyon. The concept of a massless rock foundation is treated, for which a certain part of the rock is included in the model. The dam-rock interface was modeled by contact elements, which allowed certain relative displacements between the two media of different stiffnesses. The generation of the 3D mathematical model was related to the topology of the terrain, and the nonlinear dynamic response was based on the "step-by-step" linear-acceleration direct-integration method, making use of the Wilson-θ method. The convergence process was in accordance with the Newton-Raphson method. First, the initial static effective stresses existing in the conditions of the established stationary filtration through the clayey core were defined. The analysis was based on an original FE program for the static and dynamic analyses of rock-fill dams, as well as a FE program for the solution of the stationary filtration process through the clayey core. The dynamic response of the 3D model of the dam was defined for the effect of harmonic excitations. Dynamic analyses in the linear and nonlinear domains were performed for the purpose of comparing the results. The time histories of the linear and nonlinear responses were defined for selected sections and nodes of the model, the tension cut-off zones, the plastic deformations, and the stress-shear strain relationships. The coefficient against the sliding of the potential sliding surfaces was also defined. It can be concluded that 3D analyses as well as a nonlinear material treatment of the soils built in the dam are imperative for a proper assessment of the stability of rock-fill dams situated in narrow canyons. Ključne besede: automatic generation of 3D model, rock-fill dam, nonlinear dynamic analysis, elastic perfectly plastic criterion, tension cutoff, cracking zones, plastic deformations, stability Objavljeno v DKUM: 18.05.2018; Ogledov: 1249; Prenosov: 79 Celotno besedilo (923,69 KB) Gradivo ima več datotek! Več... |
4. Wu, Yaping; Xing, Xiuxia; Ye, Qixiao: Stability of travelling waves with algebraic decay for n-degree Fisher-type equations. (English). - [J] Discrete Contin. Dyn. Syst. 16, No. 1, 47-66 (2006). [ISSN 1078-0947; ISSN 1553-5231]Miklavž Mastinšek, 2007, recenzija, prikaz knjige, kritika Ključne besede: matematika, parcialne diferencialne enačbe, asimptotična stabilnost, potujoče valovne fronte, spektralna analiza, mathematics, partial differential equations, asymptotic stability, travelling wave fronts, algebraic decay rate, spectral analysis, semigroup estimates, Evans function method Objavljeno v DKUM: 10.07.2015; Ogledov: 844; Prenosov: 38 Povezava na celotno besedilo |
5. Peng, Ji-Gen; Xu, Zong-Ben: An estimate of growth bound of positive C[sub]0-semigroup on L[sup]p space and its applicatons. - Integral Equations Oper. Theory 46, no. 4, 489-500 (2003). [ISSN 0378-620X]Miklavž Mastinšek, 2004, recenzija, prikaz knjige, kritika Ključne besede: matematika, analiza, ▫$L^p$▫ prostori, ▫$C_0$▫-polgrupa, eksponentna stabilnost, mathematics, analysis, ▫$C_0$▫-semigroup, ▫$L^p$▫ spaces, exponential stability Objavljeno v DKUM: 10.07.2015; Ogledov: 750; Prenosov: 25 Povezava na celotno besedilo |
6. Buşe, Constantin; Jitiau, Oprea: A new theorem on exponential stability of periodic evolution families on Banach spaces. - Electron. J. Differ. Equ. 2003, Paper no. 14, 10 p., electronic only (2003). [ISSN 1072-6691]Miklavž Mastinšek, 2004, recenzija, prikaz knjige, kritika Ključne besede: matematika, analiza, skoraj periodične funkcije, eksponentna stabilnost, integralska neenakost, diferencialna neenakost, Banachov prostor, mathematics, analysis, almost periodic functions, exponential stability, periodic evolution families of operators, integral inequality, differential inequality on Banach spaces Objavljeno v DKUM: 10.07.2015; Ogledov: 1010; Prenosov: 30 Povezava na celotno besedilo |