Дисертації з теми "Buckling analysi"
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1
FALLAHI, NASIM. "Analysis and Optimization of Variable Angle Tow Composites Through Unified Formulation." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2875739.
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Purbolaksono, Judha. "Buckling and post-buckling analysis of cracked plates by the boundary element method." Thesis, Queen Mary, University of London, 2003. http://qmro.qmul.ac.uk/xmlui/handle/123456789/1831.
Повний текст джерелаАнотація:
This thesis presents boundary element formulations for buckling and nonlinear buckling analysis of plates. Dual boundary element formulations are also presented for linear and nonlinear buckling, and large deformation analysis of crack behaviour in plates. Reissner plate theory is adopted to represent shear deformable plate bending, and two dimensional plane stress is used to model the membrane behaviour of plate. By taking into account the nonlinear interaction between forces and rotations in the equilibrium equation, the nonlinear formulation is formed by coupling equations of shear deformable plate bending and two dimensional elasticity. The boundary element formulation for plate buckling is developed. Plate buckling equations are written as a standard eigenvalue problem. Buckling coefficients and buckling modes are obtained using this formulation. Initially, the boundary is discretised into quadratic isoparametric elements, and the domain is discretised using constants cells. Next, the dual reciprocity method is utilized to transform the domain integral into equivalent boundary integrals. Examples are presented for plate buckling problems with different geometry, loading and boundary conditions. The results obtained are shown to be in good agreement with analytical and finite element results. The Dual Boundary Element Method (DBEM) for buckling analysis of plate is also developed. The plate buckling equations are also presented as a standard eigenvalue problem, which would allow direct evaluation of critical load factor and buckling modes for cracked plates. Geometrically nonlinear boundary element formulation is developed to analyse large deformation and nonlinear buckling of plates. Different load incremental approaches and solution procedures are presented. Nonlinear terms are evaluated using a radial basis function. Large deformation analysis for Fracture Mechanics problems is also presented. Five stress intensity factors are calculated, i. e. three for plate bending and two for membrane. Crack Opening Displacement (COD) is used to compute the stress intensity factors. The nonlinear buckling of thin plate is also presented. Two models of imperfection are introduced in the formulation, i. e. a small uniform transverse loads and distributed transverse loads based on eigenvectors. A simple numerical algorithm is presented to analyse the problems. Finally, nonlinear buckling analysis of cracked plate is presented. Numerical examples of nonlinear buckling and large deformation problems are presented. The BEM results presented are shown to be in good agreements with analytical and other numerical results.
3
Arpaci, Erdogan. "Analysis Of Sinusoidal And Helical Buckling Of Drill String In Horizontal Wells Using Finite Element Method." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12611003/index.pdf.
Повний текст джерелаАнотація:
The number of horizontal wells is increasing rapidly in all over the world with the growth of new technological developments. During horizontal well drilling, much more complex problems occur when compared with vertical well drilling, such as decrease in load transfer to the bit, tubular failure, tubular fatigue and tubular lock-up. This makes selection of appropriate tubular and making the right drill string design more important. As the total compression load on the horizontal section increases, the behavior of the tubular changes from straight to sinusoidal buckling, and if the total compression load continues to increase the behavior of the tubular changes to helical buckling. Determination of critical buckling loads with finite element method (FEM) in horizontal wells is the main objective of this study. Initially, a computer program (ANSYS) that uses FEM is employed to simulate different tubular and well conditions. Four different pipe sizes, four different wellbore sizes and three different torque values are used to model the cases. Critical buckling load values corresponding to significant variables are collected from these simulated cases. The results are classified into different buckling modes according to the applied weight on bit values and the main properties of the simulated model, such as modulus of elasticity, moment of inertia of tubular cross section, weight per unit length of tubular and radial clearance between the wellbore and the tubular. Then, the boundary equations between the buckling modes are obtained. The equations developed in this thesis by simulating the cases for the specific tubular sizes are used to make a comparison between the critical buckling load values from the models in the literature and this work. It is observed that the results of this work fit with literature models as the tubular size increases. The influence of torque on critical buckling load values is investigated. It is observed that torque has a slight effect on critical buckling load values. Also the applicability of ANSYS for buckling problems was revealed by comparing the ANSYS results with the literature models’
results and the experimental study in the literature.
4
Hashemian, Rouzbeh. "Buckling Analysis of Sandwich Pipes Under External Pressure." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31781.
Повний текст джерелаАнотація:
A general eigen-value buckling solution is developed for the buckling of long thick pipes subjected to internal and external hydrostatic pressure. The principle of stationary potential energy is used to formulate the conditions of equilibrium, neutral stability conditions, and associated boundary conditions using polar coordinates. The formulation accounts for shear deformation effects and is suited for composite pipe systems with thick cores. It involves destabilizing terms: one is due to the external hydrostatic pressure and incorporates the follower effects, and the other, is due to the pre-bucking stresses undergoing the nonlinear components of strains. The formulation adopts a work conjugate triplet consisting the Cauchy stress tensor, the Green Lagrange strain tensor, and constant constitutive relations. A Fourier series expansion of the displacement fields is adopted to transform the 2D problem into a series of independent 1D problems, thus keeping the computational effort to a minimum while preserving the accuracy of the solution. Two numerical solutions were developed and implemented under MATLAB; the first one is based on the finite difference technique and the second one is based on the finite element solution. Both solutions were shown to converge to the same solution, the finite difference from below, while the finite element converges from above.
The finite element solution is then applied to predict the buckling capacity of sandwich pipes consisting of two steel pipes with a soft core. A comprehensive verification study is conducted and the validity of the formulation was established through comparison with other solutions. A parametric study is then conducted to investigate the effect of hydrostatic internal pressure, core material, core thickness, and internal and external pipe thicknesses, on the external buckling pressure of sandwich pipes.
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Mahar, Akshay Mangal. "Buckling and post-buckling behaviour of cold-formed steel built-up columns." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232829/1/Akshay%20Mangal_Mahar_Thesis.pdf.
Повний текст джерелаАнотація:
This research investigated the stability and strength behaviour of cold-formed steel built-up columns. The stability behaviour was investigated by developing a compound spline finite strip based computational tool, while experiments and finite element studies were performed to investigate the strength behaviour. The results highlighted the shortcomings of the current design standards, including North American and Australian/New Zealand Standards, and led to simplified design procedures and strength equations for cold-formed steel built-up columns. Overall, this research has significantly improved the knowledge of cold-formed steel built-up columns, enabling structurally efficient and safer designs.
6
El-Adas, Kadmous Moufid. "Linear and nonlinear buckling analysis via ABAQUS." Master's thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-01262010-020017/.
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Wang, Yunxiao. "One-way buckling analysis of pipeline liners." Thesis, University College London (University of London), 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404888.
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Chryssanthopoulos, Marios Konstantinou. "Probabilistic buckling analysis of stringer-stiffened cylinders." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47382.
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Schleyer, Graham Klaus. "Buckling of tank roofs : a buckling analysis and experimental investigation of storage tank domed roofs." Thesis, University of Strathclyde, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362804.
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Prinz, Gary S. "Using Buckling-Restrained Braces in Eccentric Configurations." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2134.
Повний текст джерелаАнотація:
Ductile braced frames are often used to resist lateral earthquake loads in steel buildings; however the presence of a brace element can sometimes interfere with architectural features. One common type of ductile braced frame system sometimes used to accommodate architectural features is the eccentrically braced frame (EBF). In order to dissipate seismic forces, EBF beam regions (called links) must sustain large inelastic deformations. EBF links with column connections must transmit large moments and shear forces to facilitate link rotation. Experiments have shown that welded link-to-column connections tend to fracture in the link flange prior to large link rotations. This study investigated methods for improving EBF link-to-column connection performance, and proposed an alternative ductile braced frame system for accommodating architectural features. Several EBF links with reduced web and flange sections were analytically investigated using validated finite element models in ABAQUS. Results indicated that putting holes in the link web reduced stress and strain values in the link flanges at the connection, but increased the plastic strain and stress triaxiality in the web at the edges of holes. Removing area from the link flanges had little effect on connection stresses and strains. Thus, the reduced web section and reduced flange section methods are not a promising solution to the EBF link-to-column connection problem. The alternative braced frame system proposed in the dissertation used ductile beam splices and buckling-restrained braces in eccentric configurations (BRBF-Es) to accommodate architectural features. Design considerations for the BRBF-Es were determined and dynamic BRBF-E performance was compared with EBF performance. BRBF-E system and component performance was determined using multiple finite element methods. Inter-story drifts and residual drifts for the BRBF-Es were similar to those for EBFs. Results indicated that BRBF-Es are a viable alternative to the EBF, and may result in better design economy than EBFs. With the BRBF-E, damage was isolated within the brace, and in the EBF, damage was isolated within the link, indicating simpler repairs with the BRBF-E. Shop welding of BRBF-E members may replace the multiple field welds required in EBF construction.
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Murphy, A. "Accurate and efficient buckling and post buckling analysis of fuselage panels loaded in shear and compression." Thesis, Queen's University Belfast, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273230.
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Zaghian, Sepideh. "Buckling Analysis of Steel Plates Reinforced with GFRP." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32788.
Повний текст джерелаАнотація:
Glass Fiber Reinforced Polymers (GFRP) plates have recently received attention as a viable option for reinforcing existing steel members. Possible application involve web strengthening of existing plate girders and reinforcing corroded flanges and/or webs where a steel plate under combination of shear and/or normal stresses can be governed by their buckling strength. Using GFRP as a retrofit material is attractive from several respects such as easy application, achieving high additional strength with low additional weight, and corrosion resistance. Since the elastic properties of the GFRP, adhesive, and steel are orders of magnitudes apart, reliable predictions of the buckling strength of such systems necessitates careful 3D modelling involving significant modelling and computational effort. Within this context, the present study develops a simplified buckling theory for steel plates symmetrically reinforced with GFRP plates and subjected to in-plane biaxial normal stresses and shear. The theory idealizes the steel and GFRP as Kirchoff plates while accounting for the transverse shear deformations within the adhesive layers.
A variational formulation is first developed based on the principle of stationary potential energy. The validity of the variational formulation is then assessed through systematic comparisons with results based 3D finite element models for a variety of buckling problems. The variational principle thus validated, is then used to develop a finite element formulation. The new element features four nodes with five degrees of freedom per node. Results based on the finite element are compared to results based on 3D modelling to assess its validity. The element is then used to investigate the effect of GFRP thickness, adhesive thickness, and adhesive shear modulus on the critical pressure of composite systems for practical retrofitting problems.
It is shown that GFRP thickness is particularly effective in increasing the capacity of the composite system, while the effect of the adhesive layer shear modulus low to moderate. Conversely, an increase in the adhesive thickness is found to correspond to a decrease in buckling capacity of the composite system.
13
Nguyen, Thanh Truong. "Numerical modeling and buckling analysis of inflatable structures." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10123.
Повний текст джерелаАнотація:
L’objectif principal de cette thèse est de modéliser en flambement des poutres pressurisées en tissu souple homogène orthotrope (THO) composite. La première partie détaille les études expérimentales qui ont été menées sur des poutres gonflables à certain niveaux de pression afin de caractériser les propriétés mécaniques du matériau et le comportement en flambement de la structure. Dans une deuxième partie, une approche analytique a été envisagée afin d’étudier le flambement ainsi que le comportement d’une poutre gonflable orthotrope. Un modèle 3D gonflables poutre orthotrope basé sur la cinématique de Timoshenko a été présenté brièvement. La charge critique a été étudiée pour différents cas de charge avec différentes conditions aux limites. Les résultats ont été confrontés aux résultats théoriques disponibles. Pour vérifier la limite de validité des résultats, la charge d’apparition des plis a également fait l’objet d’une étude pour chacun des cas. La dernière partie est consacrée à une étude linéaire et à une analyse non-linéaire du flambement de la poutre gonflable en THO composite. Le modèle éléments finis (MEF) établi ici implique un élément poutre de Timoshenko à trois-nœuds avec une continuité de type C0. Un test de convergence du maillage sur la force critique de la poutre a été réalisé par la résolution du problème aux valeurs propres. En outre, un MEF non-linéaire a été développé en utilisant la procédure itérative de quasi-Newton avec incréments de chargement adaptatif permettant le tracé pas à pas de la réponse charge-déflexion de la poutre. Les résultats ont été validés à partir d’un certain niveau de pression par des résultats expérimentaux et numériquesThe main goals of this thesis are to modeling and to perform the buckling study of inflatable beams made from homogeneous orthotropic woven fabric (HOWF) composite. Three main scenarios were investigated in this thesis. The first is the experimental studies which were performed on HOWF inflatable beam in various inflation pressures for characterizing the orthotropic mechanical properties and buckling behaviors of the beam. In the second scenario, an analytical approach was considered to study the buckling and the behavior of an inflatable orthotropic beam. A 3D inflatable orthotropic beam model based on the Timoshenko's kinematics was briefly introduced: the nonlinearities (finite rotation, follower forces) were included in this model. The results were compared with theoretical results available in the literature. To check the limit of validity of the results, the wrinkling load was also presented in every case. The last scenario is devoted to the linear eigen and non-linear buckling analysis of inflatable beam made of HOWF. The finite element (FE) model established here involves a three-noded Timoshenko beam element with C0-type continuity for the transverse displacement and quadratic shape functions for the bending rotation and the axial displacement. In the linear buckling analysis, a mesh convergence test on the beam critical load was carried out by solving the linearized eigenvalue problem. In addition, a nonlinear FE model was developed by using the quasi-Newton iteration with adaptive load stepping for tracing load-deflection response of the beam. The results were validated from a certain pressure level by experimental and thin-shell FE results
14
Ho, Teck Tuak. "Analysis of distortional buckling in continuous composite beams." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275729.
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BUFFONI, SALETE SOUZA DE OLIVEIRA. "BUCKLING ANALYSIS OF LONGITUDINAL REINFORCEMENT IN CONCRETE COLUMNS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2004. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=5517@1.
Повний текст джерелаАнотація:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORA flambagem das armaduras longitudinais em pilares de concreto armado pode ocorrer na região entre dois estribos consecutivos, ou pode envolver um certo número de estribos. As normas de projeto existentes não fornecem uma metodologia apropriada para o dimensionamento dos estribos em diferentes situações. O presente trabalho tem por objetivo desenvolver uma formulação que permita analisar a flambagem das armaduras longitudinais em pilares de concreto armado submetidos a carregamento axial levando em conta o espaçamento entre os estribos, o diâmetro e arranjo dos estribos na seção transversal e o diâmetro das armaduras longitudinais. Para este propósito um método analítico para a avaliação da flambagem da armadura longitudinal é proposto, considerando-se as barras longitudinais restringidas pela rigidez axial ou à flexão dos estribos. Admite-se que a armadura longitudinal funciona como uma coluna esbelta. Consideram-se duas formas de modelagem da atuação dos estribos: como apoios elásticos discretos e como base elástica contínua. O presente trabalho trata a coluna com um ou mais modos de deformação, incluindo certas não- linearidades. São fornecidos cargas críticas e caminhos pós-críticos para tais casos. Como resultado deste estudo, apresenta-se uma proposta para dimensionamento racional dos estribos que permite estudar diferentes alternativas em um ábaco de utilização simples para projeto. Apresentam-se comparações com resultados experimentais da literatura em pilares de concreto armado. Isto permite uma avaliação crítica dos desenvolvimentos teóricos realizados e da forma proposta de dimensionamento racional dos estribos.
Buckling of longitudinal reinforcement in reinforced concrete columns may occur in the region between two consecutive ties, or may involve a number of ties. The existing design code specifications do not provide an appropriate methodology for the design of the transversal reinforcement in different situations. The main objective of the present work is to develop a formulation to allow to analyze the buckling of longitudinal bars in reinforced concrete columns taking into account the tie spacing, the diameter and arrangement of the ties in the cross section and the longitudinal bar diameter. For this purpose an analytical method for the evaluation of the buckling load of longitudinal bars is described, as a function of the constraint imposed by the axial or flexural stiffness of the stirrups. The longitudinal bar is considered as a column deforming according to thin beam theory. The tie action is described either by a set discrete elastic supports or by a continuous elastic foundation. The theoretical analysis considers the column with one or more deformation modes, with some degree of nonlinearity, including the analysis of post-critical equilibrium paths. As a result of this study, rational criteria for spacing and sizing of transversal reinforcement are derived, allowing to study different alternatives in an abacus of simple use for design. Several comparisons with the results obtained experimentally by other authors in reinforced concrete columns are presented, allowing for an evaluation of the validity of the theoretical developments and the rational design methodology proposed herein.
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CAVALCANTI, LILIAN DE VASCONCELLOS. "BUCKLING AND VIBRATION ANALYSIS OF SHALLOW CONOIDAL SHELLS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24636@1.
Повний текст джерелаАнотація:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROEstruturas de cascas delgadas descritas por superfícies regradas têm sido frequentemente utilizadas em engenharia civil, devido ao fato de que elas são uma das soluções estruturais mais econômicos para cobrir grandes vãos. Superfícies regradas são obtidas pelo movimento de uma ou mais linhas ao longo de uma ou mais curvas. Sendo assim, elas são fáceis de construir, o que justifica a sua escolha em muitos casos. Por razões estéticas e estruturais, estas estruturas são geralmente superfícies abatidas, o que leva, como no caso de arcos abatidos, a uma forte não linearidade geométrica. Entre as cascas descritas por superfícies regradas, as cascas conoidais são frequentemente favorecidas para coberturas de grandes áreas livres de colunas, pela facilidade de construção, elegância estética e pelo bom fornecimento de luz natural. Uma casca conoidal é um caso especial de cilindróide, pertencente às superfícies de Catalan, e é gerada por uma linha reta em movimento paralelo a um plano, conhecido como o plano diretor, com uma de suas extremidades em uma curva plana e a outra em uma linha reta. Por vezes, uma parte da superfície conoidal no extremo reto é suprimida dando origem a uma configuração truncada. O objetivo deste trabalho é analisar, utilizando uma formulação de elementos finitos, as características de flambagem e vibração desta forma estrutural. Uma análise paramétrica detalhada é realizada para compreender a influência das condições de contorno e dimensões físicas da casca no seu comportamento estático e dinâmico. São apresentadas conclusões específicas no final do trabalho, para resumir os resultados do presente estudo, que pretende servir como importante subsídio para os engenheiros envolvidos na construção de estruturas similares.
Slender shell structures described by ruled surfaces have been frequently used in civil engineering due to the fact that they are one of the most economical structural solutions to cover large spans. Ruled surfaces are obtained by the movement of one or more lines along one or more curves. So they are easy to cast, which justifies their choice in many cases. For aesthetic and structural reasons these structures are usually shallow surfaces, which leads, as in the case of shallow arches, to a strong geometric nonlinearity. Among the shells described by ruled surfaces, conoidal shells are frequently favored as roofing units to cover large column-free areas due to the ease of fabrication, aesthetic elegance and good provision of natural light. A conoidal shell is a special case of cylindroids belonging to Catalan’s surfaces and is generated by a variable straight line moving parallel to a plane, known as the director plane, with one of its ends on a plane curve and the other on a straight line. Sometimes a part of the conoidal surface at the straight end is cut off giving a truncated configuration. The objective of this work is to analyze, using a finite element formulation, the buckling and vibration characteristics of this structural form. A detailed parametric analysis is conducted to understand the influence of boundary conditions, different spans, widths, and other physical dimensions on the static and dynamic characteristics of the structure. Specific conclusions are drawn at the end, to summarize the contributions of the present investigation, which are expected to serve as important design aids to engineers engaged in shell construction.
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Chan, Cameron D. "MECHANICAL OPTIMIZATION AND BUCKLING ANALYSIS OF BIO-COMPOSITES." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/877.
Повний текст джерелаАнотація:
Today’s environmental concerns have led a renewed search in industry to find new sustainable materials to replace non-renewable resources. President Barack Obama also quoted in the recent 2012 Presidential Debate “that there is a need to build the energy sources of the future and invest in solar, wind, and bio-fuels.” Bio-composites are believed to be the future and the new substitute for non-renewable resources. Bio-composites are similar to composites in that they are made up of two constituent materials; however the main difference is that bio-composites are made from natural fibers and a biopolymer matrix. This research investigates the buckling behavior of bamboo and will analyze and determine the slender ratio that will induce buckling when bamboo is used as a column. Along with the investigation of the bamboo under buckling, this study will also show the potential of bio-composites to replace non-renewable resources in industry through experimental and numerical analysis. However, in order to study the buckling behavior of the bamboo, the mechanical characteristics of the bamboo and optimal curing treatment first had to be established. This is because, in order for bamboo to acquire proper strength characteristics, the bamboo must first be treated.
Due to the scarcity of bamboo material in the lab, the obtainment of the mechanical properties of the bamboo as well as the optimal curing treatment was done in collaboration with Jay Lopez. In order for bamboo to acquire proper strength characteristics, the bamboo must be treated. In the first study, a total of four different types of natural treatments were analyzed to optimize the mechanical characteristics of bamboo. To assess each curing method, tensile and compression tests were performed to obtain the mechanical properties. Due to each bamboo culm having different thicknesses and cross sections, the specific strength property is used to normalize the data and allow for easy comparison and assessing of each curing method equally. The specific strength parameter is defined as the ultimate stress divided by the density of the material. These curing treatments consisted of four thermo-treatments, three different percentages of salt treatments, one lime treatment, and one oil treatment. The thermo-treatments consisted of heating the bamboo internodes in an autoclave with no pressure at 150oF, 180°F, 200°F, and 220°F. The experimental results of the thermo-treatments determined that bamboo obtains higher mechanical properties as well as reduced weight when heated at higher temperatures. This is explained by the increasing bound water extracted from the bamboo material at higher temperatures. In addition to finding the optimal heat treatment, the internodes of bamboo were soaked in natural additives that included a 3%, 6%, and 9% Instant Ocean sea salt solution, a Bonide hydrated lime solution, and a Kirkland canola oil solution for approximately five days and then heat treated at the optimal temperature of 220°F. The experimental results showed that all of the different additives had a significant effect on the mechanical properties.
After determining the mechanical properties of each curing method, the results were then analyzed through a trade study. The trade study parameters consisted of weight-drop of the material, the specific strength, and the ultimate stress for both compression and tension. Each parameter of the trade study is kept unbiased as the weighting of each parameter is set equal to each other. The results of the trade study indicated that the 3% salt solution was the optimal curing treatment, yielding a higher specific strength value for both compression and tension, along with a significantly lower weight-drop after curing.
After we came up with the optimal treatment, the buckling behavior of bamboo was investigated. The buckling analysis was investigated to determine at what slenderness ratio the bamboo would buckle when used as a column. A total of seven cases were investigated using different lengths, that ranged from 1.5” to 10”. Through experimental results, it was determined that a slenderness ratio above approximately 34.7 would induce global buckling to the bamboo column.
The last investigation of this study consisted of building a small prototype wall structure using bio-composites. The prototype wall structure was manufactured using a combination of bamboo and a bi-directional woven hemp fabric. The dimensions of the prototype were 15.13” long and 7.75” tall. The wall structure was tested under compression in the Aerospace Structures/Composites Lab and the Architectural Engineering Department’s high bay laboratory. The results of the experimental test on the wall showed great potential for bio-composites, as the structure withstood a force of 46,800 pounds.
A numerical analysis technique was also employed through the finite element method using the Abaqus software. The purpose of the finite element method was to validate the experimental results by comparing the buckling behavior of the tests. The numerical analysis showed very good agreement with the experimental results.
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Smith, Frank Harrison. "Elastic buckling solutions for thin-walled metal columns with perforation patterns." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23680.
Повний текст джерелаАнотація:
Presented are approximate finite strip methods for use in predicting elastic buckling strength of cold-formed steel columns. These methods were developed by examining elemental behavior of cross-sections in eigen-buckling analyses and validated using a large database of finite element rack-type columns with perforation patterns. The influence of perforations is accounted by reduced thicknesses related to the plate buckling coefficient and transverse web rotational stiffness in the prediction of local and distortional buckling respectively. Global buckling prediction including the influence of perforations uses critical elastic loads of an unperforated section multiplied by the ratio of weighted to gross cross-sectional moment of inertia for flexural buckling and the ratios of weighted to gross cross-sectional warping torsion constant and weighted to gross St. Venant torsional constant for flexural-torsional buckling. Concern for end-user was given and methods are presented in a way for incorporation into governing design standards. Data to support these findings are available at http://hdl.handle.net/10919/23797Master of Science
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Mansour-Tehrani, F. "Studies in the mixed-mode analysis of partially prismatic thin-walled structures." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235229.
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Poy, Denise Lori-Eng 1978. "On the buckling finite element analysis of beam structures." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/89884.
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Jacob, K. I. "Three-dimensional vibration and buckling analysis of twisted parallelepipeds /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487263399024196.
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Mehta, Paras. "Asymptotic post-buckling analysis by Koiter's method with a general purpose finite element code." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-06082009-170924/.
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Pinna, Rodney. "Buckling of suction caissons during installation." University of Western Australia. School of Civil Engineering, 2003. http://theses.library.uwa.edu.au/adt-WU2004.0008.
Повний текст джерелаАнотація:
Suction caissons are a foundation system for offshore structures which offer a number of advantages over traditional piled foundations. In particular, due to the method of installation used, they are well suited for deep-water applications. The suction caisson consists of an open ended cylindrical shell, which is installed below the seabed in a sequence which consists of two loading phases. The caisson is first installed part way under self weight, with the installation being completed by lowering the pressure within the cylinder and thus allowing the ambient water pressure to force the caisson into the ground. This thesis examines a number of structural issues which result from the form of the caisson — essentially a thin walled cylinder — and the interaction of the caisson with the surrounding soil during installation. To do this, variational analysis and nonlinear finite element analysis are employed to examine the buckling and collapse behaviour of these cylinders. In particular, two issues are considered; the influence of the open end, and the interaction between the cylinder and soil on the buckling and collapse loads. First, the behaviour of open ended cylinders is considered, where the boundary condition at the open end is allowed to vary continuously from completely free to pinned, by the use of a variable lateral spring. This lateral spring restraint may be considered to represent the intermediate restraint provided by a ring stiffener which is not fully effective. The effect of various combinations of boundary conditions is accounted for by the use of a multiplier on the lower bound to the buckling load of a cylinder with classical supports. The variable spring at the open end may also be considered to be an initial, simple representation of the effect of soil restraint on the buckling load. More complex representations of the soil restraint are also considered. A nondimensional factor is proposed to account for the influence of this spring on the buckling load. One combination of boundary conditions, where the upper end of the caisson is pinned, and the lower end free (referred to as a PF boundary condition), is found to have buckling and collapse behaviour which is unusual for cylindrical shells. Buckling loads for such shells are much lower than would be found for cylinders with more typical boundary conditions, and of similar dimensions. More unusually however, PF cylinders are shown to have positive postbuckling strength. The behaviour is found to be a result of the large flexibility which results from the low restraint provided by the PF boundary conditions. This is shown by continuously decreasing the flexibility of the cylinder, by increasing the axial restraint at the pinned end. It is shown that this results in a large increase in buckling load, and a return to more usual levels of imperfection sensitivity. In particular, with an intermediate level of axial restraint, buckling loads and imperfection sensitivity are intermediate between those of PF shells with no, and with full, axial restraint. Overall however, collapse loads for PF cylinders with no additional restraint are well below those of cylinders with stiffer boundary conditions, for equal geometries. Eigenvalue buckling of cylinders fully and partially embedded in an elastic material are examined, and two analytical solutions are proposed. One of these is an extension of a method previously proposed by Seide (1962), for core filled cylinders, to pin ended cylinders which have support from both a core and a surrounding material. The second method represents the elastic support as a two parameter foundation. While more approximate than the first method, this method allows for the examination of a wider range of boundary conditions, and of partial embedment. It is found that the buckling load of the shell/soil system decreases as the embedment ratio decreases. Collapse of fully and partially embedded cylinders is also examined, using nonlinear finite element analysis. The influence of plasticity in the soil is also considered. For cylinders with small imperfections, it is found that the collapse load shows a large increase over that of the same cylinder with no soil support. However, as the size of initial geometric imperfections increases, it is found that the collapse load rapidly approaches that of the unsupported cylinder. In particular, in weak soils the gain in strength over the unsupported shell may be minimal. The exception to this is again PF cylinders. As these have relatively low collapse loads, even very weak soils are able to offer an increase in collapse load over the unsupported case. Finally, a summary of these results is provided in the form of guidance for design of such structures.
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Johnson, Barbara Helen. "Near-coincident doubly-symmetric branching systems : elastic post-buckling behaviour and imperfection sensitivity." Thesis, University of Surrey, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253986.
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Pezeshky, Payam. "Distortional Static and Buckling Analysis of Wide Flange Steel Beams." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36074.
Повний текст джерелаАнотація:
Existing design provisions in design standards and conventional analysis methods for structural steel members are based on the simplifying kinematic Vlasov assumption that neglects cross-sectional distortional effects. While the non-distortional assumption can lead to reasonable predictions of beam static response and buckling strength in common situations, past work has shown the inadequacy of such assumption in a number of situations where it may lead to over-predicting the strength of the members. The present study thus develops a series of generalized theories/solutions for the static analysis and buckling analysis of steel members with wide flange cross-sections that capture distortional effects of the web. Rather than adopting the classical Vlasov assumption that postulates the cross-section to move and rotate in its own plane as a rigid disk, the present theories assume the web to be flexible in the plane of the cross-section and thus able to bend laterally, while both flanges to move as rigid plates within the plane of the cross-section to be treated as Euler-Bernouilli beams. The theories capture shear deformation effects in the web, as well as local and global warping effects.
Based on the principle of minimum potential energy, a distortional theory is developed for the static analysis of wide flange steel beams with mono-symmetric cross-sections. The theory leads to two systems of differential equations of equilibrium. The first system consists of three coupled equilibrium differential equations that characterize the longitudinal-transverse response of the beam and the second system involves four coupled equilibrium differential equations of equilibrium and characterizes the lateral-torsional response of the beam. Closed form solutions are developed for both systems for general loading. Based on the kinematics of the new theory, two distortional finite elements are then developed. In the first element, linear and cubic Hermitian polynomials are employed to interpolate displacement fields while in the second element, the closed-form solutions developed are adopted to formulate special shape functions. For longitudinal-transverse response the elements consist of two nodes with four degree of freedom per node for longitudinal-transverse response and for lateral-torsional response, the elements consist of two nodes with eight degrees of freedom per node. The solution is able to predict the distortional deformation and stresses in a manner similar to shell solutions while keeping the modeling and computational effort to a minimum.
Applications of the new beam theory include (1) providing new insights on the response of steel beams under torsion whereby the top and bottom flanges may exhibit different angles of twist, (2) capturing the response of steel beams with a single restrained flange as may be the case when a concrete slab provides lateral and/or torsional restraint to the top flange of a steel beam, and (3) modelling the beneficial effect of transverse stiffeners in reducing distortional effects in the web.
The second part of the study develops a unified lateral torsional buckling finite element formulation for the analysis of beams with wide flange doubly symmetric cross-sections. The solution captures several non-conventional features. These include the softening effect due to web distortion, the stiffening effect induced by pre-buckling deformations, the pre-buckling nonlinear interaction between strong axis moments and axial forces, the contribution of pre-buckling shear deformation effects within the plane of the web, the destabilizing effects due to transverse loads being offset from the shear centre, and the presence of transverse stiffeners on web distortion. Within the framework of the present theory, it is possible to evoke or suppress any combination of the features and thus isolate the individual contribution of each effect or quantify the combined contributions of multiple effects on the member lateral torsional capacity. The new solution is then applied to investigate the influence of the ratios of beam span-to-depth, flange width-to-thickness, web height-to-thickness, and flange width-to-web height on the lateral torsional buckling strength of simply supported beams and cantilevers. Comparisons with conventional lateral torsional buckling solutions that omit distortional and pre-buckling effects quantify the influence of distortional and/or pre-buckling deformation effects. The theory is also used to investigate the influence of P-delta effects of beam-columns subjected to transverse and axial forces on their lateral torsional buckling resistance. The theory is used to investigate the load height effect relative to the shear centre. Comparisons are made with load height effects as predicted by non-distortional buckling theories. The solution is adopted to quantify the beneficial effect of transverse stiffeners in controlling/suppressing web distortion in beams and increasing their buckling resistance.
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Damghani, Mahdi. "Buckling behaviour of delaminated composite plates using exact stiffness analysis." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54887/.
Повний текст джерелаАнотація:
The aim of this thesis is to investigate the local and global buckling behaviour of delaminated composite plates using exact stiffness analysis. Several attempts are made to model delamination with the accuracy of detailed 3D finite element analysis (FEA) but substantially improved computational efficiency. Investigation of local buckling behaviour is performed using the exact stiffness program VICONOPT, giving good comparative results and substantially less solution times compared to those of FEA. Extending this approach to global buckling behaviour poses limitations and difficulties in retaining computational efficiency. Several techniques are introduced to study global buckling behaviour while requiring less solution time than FEA. The advantages and disadvantages of these techniques are discussed. Finally, an improved smeared stiffness method is derived which results from simplification of the total potential energy expression for the plate. This simplification avoids expensive computational effort while maintaining results of good accuracy (within 2%-3% of FEA results). This method can be employed for modelling delaminations of different shape and size located anywhere in the composite plate.
27
Sherzad, Rafiullah, and Awrangzib Imamzada. "Buckling and Geometric Nonlinear Stress Analysis : Circular glulam arched structures." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-54569.
Повний текст джерелаАнотація:
An arched structure provides an effective load carrying system for large span structures. When it comes to long span roof structures, timber arches are one of the best solutions from both structural and aesthetical point of view. Glulam arched structures are often designed using slender elements due to economic consideration. Such slender cross-section shape increases the risk of instability. Instability analysis of straight members such as beam and column are explicitly defined in Eurocode. However, for instability of curved members no analytical approach is provided in the code, thus some numerical method is required. Nonetheless, an approximation is frequently used to obtain the effective buckling length for the arched structures in the plane of arches. In this master thesis a linear buckling analysis is carried out in Abaqus to obtain an optimal effective buckling length both in-plane and out-of-plane for circular glulam arched structures. The elastic springs are used to simulate the overall stiffness of the bracing system. The results obtained by the FE simulations are compared with a simple approximation method. Besides, the forces acting on the bracings system is obtained based on 3D geometric nonlinear stress analysis of the timber trusses. Our findings conclude that the approximation method overestimates the effective buckling length for the circular glulam arched structures. In addition, the study indicates that the position of the lateral supports along the length of the arch is an important design aspect for buckling behaviour of the arched structures. Moreover, in order to acquire an effective structure lateral supports are needed both in extrados and intrados. Furthermore, instead of using elastic spring elements to simulate the overall stiffness of the bracing system, a full 3D simulation of two parallel arches was performed. It was shown that the springs are stronger than the real bracing system for the studied arch.
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Singh, Raghvendra. "Buckling analysis of delaminated composite plates with arbitrary edge conditions /." The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu14876756871766.
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Ma, Ming. "Elastic and inelastic analysis of panel collapse by stiffener buckling." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-170150/.
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Patil, Abhishek J. "Buckling analysis of a bendable composite unmanned air vehicle wing." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0025037.
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Chen, Gengbo. "Probability-Based Buckling Design of Single-Layer Reticulated Domes." Thesis, The University of Sydney, 2017. https://hdl.handle.net/2123/27507.
Повний текст джерелаАнотація:
The stability check of single-layer reticulated shells is currently based on the Allowable Strength Design (ASD) method without reliability significance. This thesis presents a comprehensive study for developing a system reliability-based design procedure for the buckling analysis of single-layer reticulated shells by advanced analysis (geometric and material nonlinear analysis with imperfections).
The impediment to adopt a probabilistic-based design method for reticulated shell structures is the difficulty in performing statistical evaluation of the buckling strength of such structures with initial geometric imperfections and semi-rigidly joint stiffness. Firstly, a random field model for the initial geometric imperfection of reticulated domes is proposed in this thesis, and probabilistic assessment of the rotational stiffness of the joint system is also carried out. Then, stochastic finite element modeling of single-layer reticulated domes can be established. In addition, the parametric sensitivity analysis is performed to study the influence of uncertainties of material property, geometry of cross-section, initial geometric imperfections, and joint stiffness on the ultimate load bearing capacity of single-layer reticulated domes. This is followed by Monte-Carlo simulations using advanced analysis are performed to obtain the statistics of the ultimate strength for a range of geometric configurations of single-layer reticulated domes. The First-Order Reliability Method (FORM) is employed to calculate resistance factors based on the Load and Resistance Factor Design (LRFD) format design formula for these single-layer reticulated domes in various geometric configurations. Finally, recommendations are made for determining the appropriate target reliability index and associated resistance factors and defining the practical advanced analysis approach for a probabilistic-based design procedure of single-layer reticulated domes.
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Beji, Faycel Ben Hedi. "Buckling Analysis of Composite Stiffened Panels and Shells in Aerospace Structure." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/81620.
Повний текст джерелаАнотація:
Stiffeners attached to composite panels and shells may significantly increase the overall buckling load of the resultant stiffened structure. Initially, an extensive literature review was conducted over the past ten years of published work wherein research was conducted on grid stiffened composite structures and stiffened panels, due to their applications in weight sensitive structures. Failure modes identified in the literature had been addressed and divided into a few categories including: buckling of the skin between stiffeners, stiffener crippling and overall buckling. Different methods have been used to predict those failures. These different methods can be divided into two main categories, the smeared stiffener method and the discrete stiffener method. Both of these methods were used and compared in this thesis. First, a buckling analysis was conducted for the case of a grid stiffened composite pressure vessel. Second, a buckling analysis was conducted under the compressive load on the composite stiffened panels for the case of one, two and three longitudinal stiffeners and then, using different parameters, stiffened panels under combined compressive and shear load for the case of one longitudinal centric stiffener and one longitudinal eccentric stiffener, two stiffeners and three stiffeners.Master of Science
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ASCIONE, ALESSIA. "Synthetic models for the analysis and control of composite and sandwich aerospace structures in critical conditions." Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2751494.
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Grall, Bruno. "Structural analysis of geodesically stiffened composite panels with variable stiffener distribution." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-12232009-020522/.
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PATTNAIK, SHRIKANT PRASAD. "PREDICTION OF BENDING WAVES IN THIN PLATES FORMED BY BUCKLING DURING ROLLING PROCESS." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1148319302.
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Avecillas, Javier Andres. "Topology Optimization of Steel Shear Fuses to Resist Buckling." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/87407.
Повний текст джерелаАнотація:
Shear-acting structural fuses are steel plates with cutouts subjected to in-plane lateral displacements during extreme loading events such as earthquakes, that dissipate energy through localized shear or flexural yielding mechanisms. Although previous studies have reported that fuses with specific geometry can develop a stable hysteretic behavior, their small thickness makes them prone to buckling, reducing strength and energy dissipation capacity.
In this work, topology optimization using genetic algorithms is performed to find optimized shapes for structural fuses with a square domain and constant thickness. The objective function uses the fuse's shear buckling load VB obtained from a 3D linear buckling analysis, and shear yield load VY obtained from a material nonlinear, but geometrically linear 2D plane-stress analysis. The two analyses are shown to be computationally efficient and viable for use in the optimization routine. The variations VY/VB=0.1,0.2,0.3 are investigated considering a target volume equal to 30%, 40% and 50% the fuse's original volume. A new set of optimized topologies are obtained, interpreted into smooth shapes, and evaluated using finite elements analyses with models subjected to monotonic and cyclic displacements histories. It was found that the drift angle when out-of-plane buckling occurs can be controlled using the VY/VB ratio, with optimized topologies buckling at drift angles (when subjected to a cyclic displacement protocol) as large as 9% as compared to 6% for previously studied fuses.Master of Science
Shear-acting structural fuses are steel plates with cutouts that dissipate energy during extreme loading events such as earthquakes. These structural fuses have a fixed edge and an opposing edge subjected to in-plane lateral displacements. Although previous studies have reported that fuses with specific geometry have a good cyclic performance, their small thickness makes them prone to bend or buckle, reducing strength and energy dissipation capacity. Considering a structural fuse with a square domain and constant thickness, a mathematical method called topology optimization is implemented to optimize the distribution of material with the goal of controlling the amount of yielding in the structural fuse before it buckles. The optimization routine uses the fuse’s shear buckling capacity (VB) and shear yield strength (VY ) obtained from relative simple and computationally inexpensive procedures that are also valid to characterize the potential for buckling in a structural fuse. The variations VY /VB = 0.1, 0.2, 0.3 are investigated considering a target volume equal to 30%, 40% and 50% the fuse’s original volume. A set of optimized topologies are interpreted into smooth shapes and evaluated using finite elements analyses. It was found that the drift angle when out-of-plane buckling occurs can be controlled by using the VY /VB ratio, with optimized topologies buckling at drift angles (when subjected to a cyclic displacement protocol) as large as 9% as compared to 6% for previously studied fuses. .
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Yuan, Zeng. "Advanced Analysis of Steel Frame Structures Subjected to Lateral Torsional Buckling Effects." Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15980/1/Zeng_Yuan_Thesis.pdf.
Повний текст джерелаАнотація:
The current design procedure for steel frame structures is a two-step process including an elastic analysis to determine design actions and a separate member capacity check. This design procedure is unable to trace the full range of load-deflection response and hence the failure modes of the frame structures can not be accurately predicted. In recent years, the development of advanced analysis methods has aimed at solving this problem by combining the analysis and design tasks into one step. Application of the new advanced analysis methods permits a comprehensive assessment of the actual
failure modes and ultimate strengths of structural steel systems in practical design
situations. One of the advanced analysis methods, the refined plastic hinge method, has shown great potential to become a practical design tool. However, at present, it is only suitable for a special class of steel frame structures that is not subject to lateral
torsional buckling effects. The refined plastic hinge analysis can directly account for three types of frame failures, gradual formation of plastic hinges, column buckling and local buckling. However, this precludes most of the steel frame structures whose behaviour is governed by lateral torsional buckling. Therefore, the aim of this research is to develop a practical advanced analysis method suitable for general steel frame structures including the effects of lateral-torsional buckling.
Lateral torsional buckling is a complex three dimensional instability phenomenon. Unlike the in-plane buckling of beam-columns, a closed form analytical solution is not available for lateral torsional buckling. The member capacity equations used in design specifications are derived mainly from testing of simply supported beams. Further, there has been very limited research into the behaviour and design of steel
frame structures subject to lateral torsional buckling failures. Therefore in order to
incorporate lateral torsional buckling effects into an advanced analysis method, a detailed study must be carried out including inelastic beam buckling failures.
This thesis contains a detailed description of research on extending the scope of advanced analysis by developing methods that include the effects of lateral torsional buckling in a nonlinear analysis formulation. It has two components. Firstly, distributed plasticity models were developed using the state-of-the-art finite element analysis programs for a range of simply supported beams and rigid frame structures to investigate and fully understand their lateral torsional buckling behavioural
characteristics. Nonlinear analyses were conducted to study the load-deflection response of these structures under lateral torsional buckling influences. It was found that the behaviour of simply supported beams and members in rigid frame structures is significantly different. In real frame structures, the connection details are a decisive factor in terms of ultimate frame capacities. Accounting for the connection rigidities in a simplified advanced analysis method is very difficult, but is most critical. Generally, the finite element analysis results of simply supported beams agree very well with the predictions of the current Australian steel structures design code AS4100, but the capacities of rigid frame structures can be significantly higher compared with Australian code predictions.
The second part of the thesis concerns the development of a two dimensional refined plastic hinge analysis which is capable of considering lateral torsional buckling effects. The formulation of the new method is based on the observations from the distributed plasticity analyses of both simply supported beams and rigid frame structures. The lateral torsional buckling effects are taken into account implicitly using a flexural stiffness reduction factor in the stiffness matrix formulation based on the member capacities specified by AS4100. Due to the lack of suitable alternatives, concepts of moment modification and effective length factors are still used for determining the member capacities. The effects of connection rigidities and restraints from adjacent members are handled by using appropriate effective length factors in the analysis. Compared with the benchmark solutions for simply supported beams, the new refined plastic hinge analysis is very accurate. For rigid frame structures, the new method is generally more conservative than the finite element models. The accuracy of the new method relies on the user's judgement of beam segment restraints. Overall, the design capacities in the new method are superior to those in the current design procedure, especially for frame structures with less slender members.
The new refined plastic hinge analysis is now able to capture four types of failure modes, plastic hinge formation, column buckling, local buckling and lateral torsional buckling. With the inclusion of lateral torsional buckling mode as proposed in this thesis, advanced analysis is one step closer to being used for general design practice.
38
Yuan, Zeng. "Advanced Analysis of Steel Frame Structures Subjected to Lateral Torsional Buckling Effects." Queensland University of Technology, 2004. http://eprints.qut.edu.au/15980/.
Повний текст джерелаАнотація:
The current design procedure for steel frame structures is a two-step process including an elastic analysis to determine design actions and a separate member capacity check. This design procedure is unable to trace the full range of load-deflection response and hence the failure modes of the frame structures can not be accurately predicted. In recent years, the development of advanced analysis methods has aimed at solving this problem by combining the analysis and design tasks into one step. Application of the new advanced analysis methods permits a comprehensive assessment of the actual failure modes and ultimate strengths of structural steel systems in practical design situations. One of the advanced analysis methods, the refined plastic hinge method, has shown great potential to become a practical design tool. However, at present, it is only suitable for a special class of steel frame structures that is not subject to lateral torsional buckling effects. The refined plastic hinge analysis can directly account for three types of frame failures, gradual formation of plastic hinges, column buckling and local buckling. However, this precludes most of the steel frame structures whose behaviour is governed by lateral torsional buckling. Therefore, the aim of this research is to develop a practical advanced analysis method suitable for general steel frame structures including the effects of lateral-torsional buckling. Lateral torsional buckling is a complex three dimensional instability phenomenon. Unlike the in-plane buckling of beam-columns, a closed form analytical solution is not available for lateral torsional buckling. The member capacity equations used in design specifications are derived mainly from testing of simply supported beams. Further, there has been very limited research into the behaviour and design of steel frame structures subject to lateral torsional buckling failures. Therefore in order to incorporate lateral torsional buckling effects into an advanced analysis method, a detailed study must be carried out including inelastic beam buckling failures. This thesis contains a detailed description of research on extending the scope of advanced analysis by developing methods that include the effects of lateral torsional buckling in a nonlinear analysis formulation. It has two components. Firstly, distributed plasticity models were developed using the state-of-the-art finite element analysis programs for a range of simply supported beams and rigid frame structures to investigate and fully understand their lateral torsional buckling behavioural characteristics. Nonlinear analyses were conducted to study the load-deflection response of these structures under lateral torsional buckling influences. It was found that the behaviour of simply supported beams and members in rigid frame structures is significantly different. In real frame structures, the connection details are a decisive factor in terms of ultimate frame capacities. Accounting for the connection rigidities in a simplified advanced analysis method is very difficult, but is most critical. Generally, the finite element analysis results of simply supported beams agree very well with the predictions of the current Australian steel structures design code AS4100, but the capacities of rigid frame structures can be significantly higher compared with Australian code predictions. The second part of the thesis concerns the development of a two dimensional refined plastic hinge analysis which is capable of considering lateral torsional buckling effects. The formulation of the new method is based on the observations from the distributed plasticity analyses of both simply supported beams and rigid frame structures. The lateral torsional buckling effects are taken into account implicitly using a flexural stiffness reduction factor in the stiffness matrix formulation based on the member capacities specified by AS4100. Due to the lack of suitable alternatives, concepts of moment modification and effective length factors are still used for determining the member capacities. The effects of connection rigidities and restraints from adjacent members are handled by using appropriate effective length factors in the analysis. Compared with the benchmark solutions for simply supported beams, the new refined plastic hinge analysis is very accurate. For rigid frame structures, the new method is generally more conservative than the finite element models. The accuracy of the new method relies on the user's judgement of beam segment restraints. Overall, the design capacities in the new method are superior to those in the current design procedure, especially for frame structures with less slender members. The new refined plastic hinge analysis is now able to capture four types of failure modes, plastic hinge formation, column buckling, local buckling and lateral torsional buckling. With the inclusion of lateral torsional buckling mode as proposed in this thesis, advanced analysis is one step closer to being used for general design practice.
39
Yuan, Qizhong. "Finite element analysis of the plastic buckling of a cantilever beam." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0001/MQ42464.pdf.
Повний текст джерела
40
Conrad, Katarina Terzic. "Analysis of the Buckling States of an Infinite Plate Conducting Current." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/29041.
Повний текст джерелаАнотація:
In this thesis we analyze the buckling behavior of an infinitely long, thin, uniform, inextensible, elastic plate that has a steady current flowing along its length.
We are concerned with the derivation of the nonlinear equations of motion using nonlinear continuum mechanics, and subsequent analysis of the buckling behavior of the plate under electromagnetic self-forces. In particular, we concentrate on how the body-forces that result from the applied current determine the buckled configurations. We derive both analytical and numerical results, and in the process develop a novel boundary value problem solver for integro-differential equations in addition to a predictor-corrector algorithm to continue solutions with respect to the control parameters.
We take a relatively complex problem in magneto-solid mechanics and elasticity theory and form a realistic model that sheds light on the bifurcation and buckling behavior resulting from the electromagnetic-field- induced self-forces that are derived in their full, exact form using Biot-Savart Law.Ph. D.
41
Vallejos, Augusto, Shammely Ayala, and Roman Arciniega. "Improved First Order Formulation for Buckling Analysis of Functionally Graded Beams." Institute of Electrical and Electronics Engineers Inc, 2020. http://hdl.handle.net/10757/656419.
Повний текст джерелаАнотація:
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.In this research, an improved first order formulation is presented to study the critical buckling load in functionally graded beams. The formulation has five independent variables in comparison with the Timoshenko theory that has three. The Trefftz criterion is utilized with incremental and fundamental states to define the stability analysis. Virtual work statements are derived for the finite element model where the field variables are interpolated by Lagrange polynomials. The numerical results are compared and verified with other formulations found in literature. Parametric studies are also carried out for buckling behavior due to different slenderness ratios, power-law indices and boundary conditions. Applications of the model to functionally graded materials show the validity of the present approach.
42
Uzman, Burak Jr. "Thermal Analysis and Response of Grid-Stiffened Composite Panels." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/31381.
Повний текст джерелаАнотація:
A study aimed at determining the thermal deformation response and thermal buckling loads of rectangular grid-stiffened composite panels is presented. Two edge conditions are considered for the panel, one in which all panel edges are free to deform, and another when all the edges are restrained.
In the first case panel deformations due to a uniformly distributed thermal load are analyzed. In the latter case, thermal loads causing buckling failure due to the suppressed in-plane deformations are determined.
The panel is composed of a skin and a network of stiffeners, which are all made of the same graphite-epoxy composite material. Kirchhoff's Theory is used to determine the pre-buckling deformations and load distributions of the composite laminates for a panel with free to deform edges. To illustrate both the in-plane and out-of-plane deformations of plate structures under uniform thermal loads, two thermal coefficient vectors, thermal expansion and thermal bending coefficient vectors are introduced.
Linear panel buckling analysis performed by assuming a linear undeformed prebuckling state. Rayleigh-Ritz Method, which utilizes minimization of the total energy of a structure to determine the buckling loads, is used to govern the buckling analysis of composite laminates forming the panel. Lagrange Multiplier Method is used along with the Rayleigh-Ritz Method to enforce the deformation continuity constraints at discrete locations along the skin and stiffener interface.
As a result, graphical and numerical presentations of the effects of skin and stiffener laminate stacking sequences on the thermal deformations and on the thermal buckling load of the grid-stiffened panel are given.Master of Science
43
Sonawane, Mahesh. "Buckling analysis of singly curved shallow bi-layered arch under concentrated loading." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1576.
Повний текст джерела
44
Qin, Yi. "Numerical analysis of inelastic local web buckling capacity of coped steel I-beam." Thesis, University of Macau, 2012. http://umaclib3.umac.mo/record=b2586272.
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45
Hirst, Paul B. "Buckling behaviour of slender structural elements under interactive axial static and cyclic loading." Thesis, Sheffield Hallam University, 1987. http://shura.shu.ac.uk/19797/.
Повний текст джерелаАнотація:
The objective of the research programme has been to investigate the effects of pre-buckling low frequency inelastic cyclic hysteresis upon a range of imperfection sensitive circular hollow section struts. The programme has involved experimental and theoretical studies and computer graphics are widely employed throughout. The subject matter is introduced from a variety of perspectives, phenomenological, historical, theoretical and experimental in Chapter 1, together with an appreciation of therole of the digital computer within the research programme. Experimental factors are initially presented in Chapter 2 whilst the formal testing programme is described in Chapter 3. Original findings are definitively set out in Sections 3.3 and 3.7 wherein the concept of the 'cyclic step' is first introduced, theremaining sections in the chapter providing the necessary supporting data. Theoretical studies are reported in Chapter 4 with the novel moment-thrust-curvature modelling described in Sections 4.2 and 4.3 being of central importance. This modelling enables the formulation of a predictive cyclic strut system effectivelyrequiring of the end user the solution of only a pair of simultaneous equations and yet capable of providing data trends consistent with the experimental findings. Design interpretation together with an overview of the experimental and theoretical studies and their interrelationshipare set out in Chapter 5. A practical design procedure oriented about the effect of a pre-buckling cyclic action phase upon otherwise static strut performance is delineated and anappropriate design chart is provided. Conclusions are drawn with respect to the primary researchfindings in Chapter 6 wherein suggestions are also made regarding possible further studies. An Appendix is included providing the bibliography, nomenclature and respective published work; selected supporting documentation is also presented.
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Maria, Joseph Amal Jerald Joseph. "Directional Actuation Induced by Interactive Buckling in Slender Structures with Imperfections." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555525058577127.
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CHEN, WEN-JI, and 陳文吉. "Analysis of laminated composite plates and shell panels:vibration, buckling, and thermal buckling." Thesis, 1992. http://ndltd.ncl.edu.tw/handle/43436673787665819682.
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Huang, Chun-Sung, and 黃竣淞. "The Buckling Analysis of Countersink Driller." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/357su7.
Повний текст джерелаАнотація:
碩士國立高雄應用科技大學
模具系碩士在職專班
103
Countersink drillers can be used to machine countersink holes of various diameters. To drill a step hole, a small diameter drill is first used to make a small diameter hole, and then a large diameter drill is used for drilling a large diameter hole. This machining method is widely applied in the industry, and its main purpose is to allow the countersink hole to be used for fastener purpose. It is an improvement over the conventional drilling method of a countersink hole that requires two drilling processes. However, improper drilling data, hard-to-cut material as well as external environment factors may often cause the drilling process stop inappropriately. If the drilling spindle continues going downward, it can cause the driller to twist and break, which will damage the drilling tool and severely affect the machining process. This study conducts a static buckling analysis of countersink drills, and explores the changes in static buckling strength of small and large drills with different diameter to length ratios. This study first employs Euler’s critical buckling formula to calculate the theoretical critical buckling values. After conducting a numerical analysis by using ANSYS, the data is validated to be reliable within a margin error within 2%. Analysis is carried out for both 180 degree and 90 degree countersink drillers, and a L9(34) orthogonal arrays of the Taguchi Method is used with 4 factors: the small diameter, the large diameter, the length of the small diameter tip and the length of large one. Each factor has 3 levels in association with the industry standard. Analysis results show that the critical buckling value is higher when the drill and tip have a larger diameter and shorter length. This is consistent with Euler’s theory. However, if the ratio between the diameter of the tip and drill exceeds the ratio between the diameter and length of the tip, the critical buckling strength will decrease. The influence of each of the 4 factors, which slightly differs by countersink drill and boundary conditions, is: tip’s diameter 52%, tip’s length 26%, drill’s diameter 14%, and drill’s length 8%. It is apparent that the tip’s diameter has the greatest influence on the static buckling strength. When the tip’s diameter is too small, it can easily twist and break. Observing the critical buckling average, the 180-degree countersink drill has a slightly higher critical buckling value than the 90-degree countersink drill. Furthermore, when compared with a typical M4 one-diameter drill, the buckling strength of a M4 countersink drill is 4 times stronger.
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Ruei-SianWang and 王芮嫻. "Buckling Analysis of Composite Wing Structures." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/20086154968235221609.
Повний текст джерелаАнотація:
碩士國立成功大學
航空太空工程學系碩博士班
98
Several different structural models have been proposed to study composite wing structures such as isotropic beam model,laminated beam model, box model and plate model. By following the study of Moh and Hwu (1997) on composite sandwich plate, in this thesis we use the Rayleigh-Ritz method to attain the buckling load of composite sandwich plates.With the consideration of the airfoil shape, the results were further extended to composite wing structures. Finally a computer program was coded with MATLAB to conduct the buckling analysis,and the results were compared with those obtained by the finite element software ANSYS.
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Li, Ming-Shing, and 李明興. "Buckling Analysis of Plates Using SCM." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/09498665396665969457.
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