Metoda končnih elementov za račun mejne nosilnosti in lokalizirane porušitve ploskovnih konstrukcij

doktorska disertacija

Jaka Dujc (Author), Boštjan Brank (Mentor), Matjaž Mikoš (Thesis defence commission member), Miran Saje (Thesis defence commission member), Jože Korelc (Thesis defence commission member), Delphine Brancherie (Thesis defence commission member), Adnan Ibrahimbegović (Co-mentor)

Abstract

Keywords

civil enginering;doctoral thrsis;structures;finite element method;reinforced concrete;steel;stress resultants;elastoplasticity;localized failure;embedded discontinuity;

Data

Language:	English
Year of publishing:	2010
Source:	Ljubljana
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FGG - Faculty of Civil and Geodetic Engineering
Publisher:	[J. Dujc]
UDC:	519.63:624.073(043.3)
COBISS:	5005153
Views:	2518
Downloads:	797
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Other data

Secondary language:	Slovenian
Secondary title:	Finite element analysis of limit load and localized failure of structures
Secondary abstract:	The dissertation deals with limit load and limit ductility analysis of structures by the ﬁnite element method. When structure is at its limit load, several structural components behave inelastically, while in the critical parts of the structure, due to localization of inelastic strains, failure of material appears. Localized eﬀects in brittle materials are related to appearance and formation of a large (macro) crack, while failure in ductile materials is governed by localized shear bands. The study of limit load is thus related to modeling both standard inelastic ma- terial eﬀects, as well as modeling of localized failure of material, often reﬀered to as material softening. Standard inelastic material eﬀects are in this work described with elastoplastic, elas- toviscoplastic and nonlinear elastic material models. All the material models are deﬁned at the level of stress-resultants. Several mathematical approaches and numerical algorithms for modeling localized eﬀects are at hand, but they are often ineﬃcient or inaccurate. Therefor, we use an up-to-date approach, based on a ﬁnite element method with embedded discontinuity. We derive new ﬁnite element formulations with a quite complex kinematics of the basic elements, as well as rather complex description of discontinuous displacement ﬁelds. We derived several ﬁnite element formulations for analysis of diﬀerent structural components. First we present a ﬁnite element for limit load analysis of reinforced concrete plates. Stress-resultant elastoplas- tic and elastoviscoplastic plate ﬁnite element formulation along with a uniﬁed computational procedure that covers both formulations are presented next. Further, a nonlinear shell ﬁnite ele- ment, based on a two-surface yield function, that includes both isotropic and kinematic material hardening is presented. The last two ﬁnite elements derived in this work are intended to model the localized failure in planar beams and 2D solids. The embedded discontinuity in rotations was built into elastoplastic Euler-Bernoulli beam ﬁnite element, and a procedure, based on a precomputed analysis of a part of a structure, by using a reﬁned numerical model, is proposed to obtain the beam constitutive model parameters. Finally, we derive an elastoplastic quadri- lateral two-dimensional ﬁnite element formulation with embedded strong discontinuity, whose kinematics can model linear jumps in both normal and tangential displacements along the dis- continuity line. Numerical simulations show, that the derived ﬁnite elements, along with the accompanied numerical algorithms, are an eﬃcient and a rather robust tool for limit load and failure analysis of structures. Among other examples, we present a simulation of crack growth in brittle material and a simulation of shear band failure in ductile material. All the computer codes of the ﬁnite element formulations presented in this work have been generated through the symbolic programming of the ﬁnite element computer code and the expression optimization in AceGen computer program. The performance of these elements has been presented in numerous numerical examples, all performed by the AceFem computer program.
Secondary keywords:	gradbeništvo;disertacije;konstrukcije;metoda končnih elementov;armirani beton;jeklo;rezultante napetosti;elastoplastičnost;lokalna porušitev;vključena nezveznost;Gradbene konstrukcije;Disertacije;Nosilnost;
URN:	URN:NBN:SI
File type:	application/pdf
Type (COBISS):	Dissertation
Thesis comment:	Univ. Ljubljana, Fak. za gradbeništvo in geodezijo
Pages:	XX, 211 str.
Keywords (UDC):	mathematics;natural sciences;naravoslovne vede;matematika;mathematics;matematika;computational mathematics;numerical analysis;računska matematika;numerična analiza;applied sciences;medicine;technology;uporabne znanosti;medicina;tehnika;engineering;technology in general;inženirstvo;tehnologija na splošno;civil and structural engineering in general;gradbena tehnika;gradbeništvo;structural elements;load-bearing members;gradbene konstrukcije;
ID:	26098