Nelinearna analiza večslojnih kompozitnih konstrukcij

doktorska disertacija

Aleš Kroflič (Author), Goran Turk (Mentor), Matjaž Mikoš (Thesis defence commission member), Franc Kosel (Thesis defence commission member), Igor Planinc (Thesis defence commission member), Sebastjan Bratina (Thesis defence commission member), Bojan Čas (Co-mentor)

Abstract

Keywords

gradbeništvo;disertacije;večslojni kompozitni nosilec;zdrsi;razmiki;lezenje in krčenje;mehčanje;elastični uklon;metoda končnih elementov;analitične rešitve;

Data

Language:	Slovenian
Year of publishing:	2012
Source:	Ljubljana
Typology:	2.08 - Doctoral Dissertation
Organization:	UL FGG - Faculty of Civil and Geodetic Engineering
Publisher:	[A. Kroflič]
UDC:	624.016:624.072.2(043.3)
COBISS:	5774689
Views:	2118
Downloads:	696
Average score:	0 (0 votes)
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Other data

Secondary language:	English
Secondary title:	Non-linear analysis of multilayer composite structures
Secondary abstract:	A new mathematical model for non-linear static analysis of multilayer composite structures with deformable connection is presented. Doctoral thesis is divided into two parts. In the first part a new mathematical model for analysis of plane multilayer frames is presented. Each layer of composite frame is modelled with geometrically exact Reissner model of plane beam. An important novelty of the model is the introduction of a new constitutive law for connection. Arbitrary non-linear relationship between stress vector and vector of displacement differences at the contact is described in the average base. This constitutive law presents a physically reasonable generalization of constitutitve laws known from linear models of two-layer beams which are described in spatial base. The basic system of non-linear equilibrium equations which represents mathematical model is solved by Galerkin's finite element method. A new family of strain-based finite elements is presented. A new numerical method for analysis of multilayer plane composite structures is very accurate and therefore suitable for analysis of stiffness, ductility, ultimate capacity and buckling capacity of different types of multilayer composite structures used in civil engineering. Detailed parametric study revealed that shear and transverse connection stiffness have a major effect on buckling capacity of composite columns. The effect of transverse connection is negligible comparing to the effect of shear connection in the case of bending of multilayer composite frames. The influence of transverse connection stiffness is negligible when composite beams are subjected to bending. The exact solution of buckling capacity of completly debonded elastic spatial beams with straight axis and pre-twisted beams is presented in the second part of the doctoral thesis. The solution is derived based on consistent linearization of Reissner-Simo's spatial beam model and the fact that critical points of linearized system of equations are equal to the critical points of corresponding non-linear system of equations. Parametric studies revealed that initial twist of cross-sections, length and position of delaminated parts have an important effect on buckling capacity of fully delaminated elastic spatial beams. The buckling capacity is higher in the case of twisted columns.
Secondary keywords:	doctoral thesis;multilayer composite beam;slip;uplift;creep and shrinkage;softening;elastic;buckling;finite element method;analytical solution;
URN:	URN:NBN:SI
File type:	application/pdf
Type (COBISS):	Dissertation
Thesis comment:	Univ. v Ljubljani, Fak. za gradbeništvo in geodezijo
Pages:	XX, 104 str.
Type (ePrints):	thesis
Title (ePrints):	Non-linear analysis of multilayer composite structures
Keywords (ePrints):	večslojni kompozitni nosilec;zdrs;razmik;lezenje in krčenje;mehčanje;elastični uklon;metoda končnih elementov;analitična rešitev
Keywords (ePrints, secondary language):	multilayer composite beam;slip;uplift;creep and shrinkage;softening;elastic;buckling;finite element method;analytical solution
Abstract (ePrints):	V doktorski disertaciji je prikazan nov numerični model za nelinearno statično analizo večslojnih linijskih kompozitnih konstrukcij s podajnimi veznimi sredstvi. Vsebinsko je disertacija razdeljena na dva dela. V prvem delu je predstavljen numerični model za analizo ravninskih večslojnih okvirjev. V prikazanem modelu je vsak sloj kompozitnega okvirja modeliran z geometrijsko točnim Reissnerjevim modelom ravninskega nosilca. Pomembna novost modela je vpeljava konstitutivnega zakona veznih sredstev. Zakon, ki predstavlja poljubno nelinearno zvezo med vektorjem napetosti in vektorjem razlike pomikov na stiku med sloji, je zapisan v povprečni bazi. Tak zapis omogoča fizikalno smiselno posplošitev konstitutivnih zakonov veznih sredstev, ki so poznani pri linearnih modelih dvoslojnih linijskih nosilcev, kjer je zakon zapisan v prostorski bazi. Osnovni sistem nelinearnih ravnotežnih enačb matematičnega modela je v disertaciji rešen z Galerkinovo metodo končnih elementov. Predstavljena je nova družina deformacijskih končnih elementov. Nova numerična metoda za analizo večslojnih ravninskih kompozitnih okvirjev je zelo natančna in zato primerna za analizo togosti, duktilnosti, nosilnosti in uklonske nosilnosti vseh vrst večslojnih kompozitnih okvirjev, ki se uporabljajo v gradbeništvu. Detajlna parametrična analiza je pokazala, da imata prečna in vzdolžna togost stika velik vpliv na uklonsko nosilnost kompozitnih stebrov ter da je vpliv prečne togosti stika v primerjavi z vzdolžno togostjo stika pri upogibno obremenjenih večslojnih kompozitnih okvirjih zanemarljiv. V drugem delu doktorske disertacije je predstavljena točna rešitev uklonskih sil pri popolnoma razslojenih elastičnih ravnih prostorskih stebrih in elastičnih zavitih prostorskih stebrih. Točna rešitev je izpeljana z uporabo konsistentne linearizacije Reissner-Simovega matematičnega modela prostorskega nosilca in dejstva, da so kritične točke nelinearnega sistema enačb enake kritičnim točkam pripadajočega lineariziranega sistema enačb. S parametričnimi študijami je bilo ugotovljeno, da dolžina, lega in orientacija razslojenih delov prostorskih elastičnih stebrov pomembno vplivajo na njihovo uklonsko nosilnost ter, da je uklonska nosilnost zavitih stebrov večja od uklonske nosilnosti ravnih stebrov.
Abstract (ePrints, secondary language):	A new mathematical model for non-linear static analysis of multilayer composite structures with deformable connection is presented. Doctoral thesis is divided into two parts. In the first part a new mathematical model for analysis of plane multilayer frames is presented. Each layer of composite frame is modelled with geometrically exact Reissner model of plane beam. An important novelty of the model is the introduction of a new constitutive law for connection. Arbitrary non-linear relationship between stress vector and vector of displacement differences at the contact is described in the average base. This constitutive law presents a physically reasonable generalization of constitutitve laws known from linear models of two-layer beams which are described in spatial base. The basic system of non-linear equilibrium equations which represents mathematical model is solved by Galerkin's finite element method. A new family of strain-based finite elements is presented. A new numerical method for analysis of multilayer plane composite structures is very accurate and therefore suitable for analysis of stiffness, ductility, ultimate capacity and buckling capacity of different types of multilayer composite structures used in civil engineering. Detailed parametric study revealed that shear and transverse connection stiffness have a major effect on buckling capacity of composite columns. The effect of transverse connection is negligible comparing to the effect of shear connection in the case of bending of multilayer composite frames. The influence of transverse connection stiffness is negligible when composite beams are subjected to bending. The exact solution of buckling capacity of completly debonded elastic spatial beams with straight axis and pre-twisted beams is presented in the second part of the doctoral thesis. The solution is derived based on consistent linearization of Reissner-Simo's spatial beam model and the fact that critical points of linearized system of equations are equal to the critical points of corresponding non-linear system of equations. Parametric studies revealed that initial twist of cross-sections, length and position of delaminated parts have an important effect on buckling capacity of fully delaminated elastic spatial beams. The buckling capacity is higher in the case of twisted columns.
Keywords (ePrints, secondary language):	multilayer composite beam;slip;uplift;creep and shrinkage;softening;elastic;buckling;finite element method;analytical solution
ID:	8312386