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: 18.05.2018; Ogledov: 921; Prenosov: 59
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Decision making under conditions of uncertainty in agricultureKarmen Pažek
, Črtomir Rozman
, 2009, pregledni znanstveni članek
Opis: In decision under uncertainty individual decision makers (farmers) have to choose one of a set number of alternatives with complete information about their outcomes but in the absence of any information or data about the probabilities of the various state of nature. This paper examines a decision making under uncertainty in agriculture. The classical approaches of Wald’s, Hurwicz’s, Maximax, Savage’s and Laplace’s are discussed and compared in case study of oil pumpkin production and selling of pumpkin oil. The computational complexity and usefulness of the criterion are further presented. The article is concluded with aggregate the results of all observed criteria and business alternatives in the conditions of uncertainty, where the business alternative 1 is suggested.
Ključne besede: uncertainty, Wald’s, Hurwicz’s, Maximax, Savage’s and Laplace’s criterion, decision support system, agriculture, oil crops
Objavljeno: 20.07.2017; Ogledov: 549; Prenosov: 76
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Evaluation of stress intensity factors using finite elementsBoštjan Zafošnik
, Zoran Ren
, Miran Ulbin
, Jože Flašker
, 2002, objavljeni znanstveni prispevek na konferenci
Opis: The paper describes a suitability of Virtual Crack Extension (VCE) method for numerical simulation of crack propagation under mixed mode loading. The suitability of VCE method was determined using The Compact-Tension-Shear (CTS), which is subjected to fracture Mode I, Mode II or mixed mode (Mode I + Mode II) loading. In mixed mode the crack kinks when fracture crack growth occurs. Kink angle is determined with VCE method, which is an energy method, maximum tangential stress (MTS) criterion, strain energy density (SED) criterion and experimental results. Determination of crack propagation angle using MTS and SED criterion is based in regard to the stress intensity factors KI and KII. Stress intensity factors are determined using the maximum energy release rate theory using complex J integral, crack opening displacement method and method of stresses extrapolation. Bigger is the rate between KII and KI, crack path, determined with VCE method, propagates more slowly to the kink angle, determined with experiment. The computational results show that the VCE method is suitable for crack propagation, when KI around the crack tip is dominant. In case where KII is dominant, crack does not kink immediately as in other two criteria. When KII dominates around a crack tip, MTS criterion is the most appropriate for determination of kink angle.
Ključne besede: fracture mechanics, stress intensity factors, CTS specimen, crack propagation, virtual crack extension method, strain energy density criterion, maximum tangential stress criterion
Objavljeno: 01.06.2012; Ogledov: 1839; Prenosov: 28
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An alternative sorting procedure for interactive group decision support based on the pseudo-criterion conceptAndrej Bregar
, József Györkös
, Ivan Rozman
, 2003, izvirni znanstveni članek
Opis: An original interactive procedure is proposed, which aims at overcoming some of the major weaknesses of existent pseudocriterion based methods for group decision analysis. It refers to absolute judgements of feasible alternatives and is focused on complementary activities of opinion elicitation and robustness analysis. As a foundation, four interdependent principles are introduced - problem localization, interactivity on the basis of aggregation/disaggregation approach, automatic derivation of criteria weights according to selective effects of veto tresholds, and group consensus seeking. The principles are grounded and realized by appropriate methodological solutions.
Ključne besede: decision analysis, pseudo-criterion concept, decision models, group consensus, alternative sorting, group work, fuzzy relation
Objavljeno: 01.06.2012; Ogledov: 1243; Prenosov: 54
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