Showing papers in "Thin-walled Structures in 1994"
TL;DR: In this paper, the basic equations for second-order generalized beam theory are outlined, and solutions for pin-ended supports are presented, demonstrating the coupling effect by modes and by loads.
Abstract: First-order generalized beam theory describes the behaviour of prismatic structures by ordinary uncoupled differential equations, using deformation functions for bending, torsion and distortion. In second-order theory, the differential equations are coupled by the effect of deviating forces. The basic equations for second-order generalized beam theory are outlined. Solutions for pin-ended supports are presented, demonstrating the coupling effect by modes and by loads. In the different ranges of length, the individual modes are sufficient approximations for the critical load. The application to a thin-walled bar with C-section under eccentric normal force demonstrates the quality of the single-mode compared to the exact solution.
220 citations
TL;DR: In this article, a design equation for fiber reinforced plastic columns is presented based on the interaction between local and global buckling observed during testing of the FRP columns included in this investigation.
Abstract: A design equation for fiber reinforced plastic columns is presented in this paper, based on the interaction between local (flange) and global (Euler) buckling observed during testing of the FRP columns included in this investigation. An existing interaction equation is adapted to account for the modes of failure observed in columns made of fiber reinforced composite materials. Experimental data generated during this investigation are presented and used to validate the interaction equation and to obtain the interaction constant. A slenderness ratio is proposed and used to present a plot of buckling for all sections and column lengths (short, long, and intermediate). An expression for the optimum column length to be used in the experimental determination of the interaction constant is proposed.
97 citations
TL;DR: In this article, a new data reduction technique using Southwell's method is developed to interpret local buckling test data, and the usefulness of the data reduction method is demonstrated for various column sections and experimental conditions.
Abstract: In this paper, local flange-buckling of thin-walled pultruded FRP columns is investigated. Experimental data are presented and correlated with theoretical predictions. Good agreement between theoretical and experimental results is found. Possible explanations for slight deviations in the experimental data are advanced. The experimental and data reduction procedures used to obtain the local buckling loads are presented. A new data reduction technique using Southwell's method is developed to interpret local buckling test data. The usefulness of the data reduction technique is demonstrated for various column sections and experimental conditions.
83 citations
TL;DR: In this paper, an overview of the up-to-date state of the coupled instabilities theory in the light of extensive recent developments in the research has been given, with an introductory review of the principal aspects, phenomenon, theory and methods, followed by application to structural elements and structures.
Abstract: The author gives an overall view of the up-to-date state of the coupled instabilities theory in the light of extensive recent developments in the research. The introductory review of the principal aspects, phenomenon, theory and methods, is followed by application to structural elements and structures. The second part refers to papers presented at the conference. The bibliography contains over 230 papers.
60 citations
TL;DR: In this paper, the free vibration of a toroidal shell (curved pipe) is studied using DMV (Donnell-Mushtari-Vlasov) thin shell theory, Fourier's series and Galerkin's method.
Abstract: The free vibration of a toroidal shell (curved pipe) is studied using DMV (Donnell-Mushtari-Vlasov) thin shell theory, Fourier's series and Galerkin's method. Some behaviors of the vibration of cylindrical shell, as a special case of toroidal shell, are discussed. Also, a 90-degree-bend curved pipe is studied numerically. Results obtained by the present method are compared to those obtained by finite element and other methods. DMV linear thin shell theory is employed for simplicity. However, the method applies to any other shell theories without difficulties.
43 citations
TL;DR: In this article, the authors focus on the description of an analytical web crippling model and the comparison of the model and tests results and much attention is paid to a better understanding of the web crippling behavior.
Abstract: Cold-formed, thin-walled flexural steel members are frequently used as structural elements in buildings. When such a member is subjected to a concentrated load or reaction, its web may cripple due to the high local intensity of the load. This type of failure is denoted as web crippling. This paper focuses on the description of an analytical web crippling model and the comparison of the model and tests results. Much attention is paid to a better understanding of the web crippling behavior.
31 citations
TL;DR: In this article, the influence on the elastic buckling load of trapezoidally corrugated panels under in-plane loading is analyzed by a spline finite strip method.
Abstract: Buckling of trapezoidally corrugated panels under in-plane loading is analyzed by a spline finite strip method. The influence on the elastic buckling load of various parameters, such as geometry. loading forms and boundary conditions, etc., is studied. It is found that: (1) for longitudinal compression the buckling load increases with the corrugation angle α, and for a given α the highest buckling load is achieved when the ‘proportion parameter’ γ = 1 ; (2) for shear loading the buckling load increases as α increases, and for a given α the highest buckling load is obtained when γ = 2 ; and (3) for a combined loading of compression and shear, interactive curves can be approximated by unit circles when α = 15°, 30°, 45°, 60° and 90° . However, when α = 75° a parabola seems to be a better approximation. Based on the numerical experiments, simplified formulae and interactive curves are suggested for practical design.
31 citations
TL;DR: In this article, the local buckling behavior of hybrid beams, with high-strength steel webs and mild steel flanges, is investigated, and the results of investigation are presented in Table 1.
Abstract: In this paper, the local buckling behavior of hybrid beams, with high-strength steel webs and mild steel flanges, is investigated. A wide-flange shaped member is essentially an assemblage of plate elements and then the plate buckling has a significant effect on the plastic deformation capacity of a beam, while the web provides the flange with some degree of rotational restraint against local buckling. The torsional restraint of the web against the flange inelastic buckling depends on the web stiffness, namely, the length of the plastic region in the web. A hybrid beam with high-strength steel webs and mild steel flanges is considered to be effective in carrying loads after the flange local buckling. The results of investigation are presented herein.
27 citations
TL;DR: In this article, the Von Karman theory has been used for the description of the postbuckling behaviour of a thin-walled panel with imperfections and residual stresses using Hamilton's principle in incremental form.
Abstract: Von Karman theory has been used for the description of the post-buckling behaviour of a thin-walled panel with imperfections and residual stresses Using Hamilton's principle in incremental form the problem of the free vibration has been established Illustrative examples of the buckling of a column and a slender web loaded in compression emphasizing different types of support in the direction of the column axis or the neutral surface of the slender web are presented The influence of the mode of the geometrical imperfection is shown and an approximate solution taking into account the residual stresses is presented
24 citations
TL;DR: In this paper, a comparison of design strengths of thin-walled plain channel section columns, which have slender flanges and may undergo local buckling, with tests and analytical ultimate loads is presented.
Abstract: The paper presents a comparison of design strengths of thin-walled plain channel section columns, which have slender flanges and may undergo local buckling, with tests and analytical ultimate loads. The design strengths are obtained using the British, American and Australian specifications for cold-formed steel structure. The comparison is shown for fixed-ended and pin-ended columns. A simple design procedure is presented for plain channel section columns. By introducing a ‘pin-ended stub column strength’, it is possible to calculate accurately the strength of concentrically loaded pin-ended columns without resorting to a beam-column design approach. It is also possible to account for the different effects of local buckling on the strengths of pin-ended and fixed-ended columns.
22 citations
TL;DR: In this paper, the free-vibration natural frequencies of circular arches subtending a considerable range of central angles and having a wide range of ratios of radius of curvature to radius of gyration (R r ) are obtained.
Abstract: The free-vibration natural frequencies of circular arches subtending a considerable range of central angles and having a wide range of ratios of radius of curvature to radius of gyration ( R r ) are obtained. Both symmetrical and antisymmetrical modes of vibration are investigated and the crossover values of frequencies from one of the modes to the other are obtained. Arches that are fixed at both ends, hinged at both ends and one end fixed whilst the other is pinned are analysed. The finite element method is employed to obtain these results. A strain-based curved beam element, using Timoshenko's deep-beam formulation in a system of curvilinear coordinates, is obtained and employed in the analysis. It is shown that this element does not have any spurious constraints and locking characteristics. Convergence curves show that accurate and stable results are obtained by the use of few elements, enabling the employment of a simple method of obtaining the eigenvalues and eigenvectors representing the frequencies and the corresponding modes of vibrations, respectively.
TL;DR: In this article, a plastic hinge analysis based on a two-surface stiffness degradation model is presented for second-order inelastic analysis of steel structures. But the analysis approach is based on refinements to the elastic-plastic hinge method and allows for a smooth transition from initial yielding to the full yielding of cross-sections in a beamcolumn element.
Abstract: A plastic hinge analysis based on a two-surface stiffness degradation model is outlined for second-order inelastic analysis of steel structures. The analysis approach is based on refinements to the elastic-plastic hinge method and allows for a smooth transition from initial yielding to the full yielding of cross-sections in a beam-column element. This analysis method shows a good representation of the inelastic structural response compared to the conventional elastic-plastic hinge analysis, and it is efficient for use in the analysis design of large-scale structures. Design implications, recommendations and case studies for use of refined plastic hinge analysis for direct frame design considering semirigid connection effects are presented.
TL;DR: In this article, the second-order generalized beam theory is used to calculate the cross-section distortion properties of a thin-walled section considering both rigid body movement and cross-sectional distortion.
Abstract: A previous paper presented a method of analysis for any open unbranched thin-walled section considering both rigid body movement and cross-section distortion (including local buckling). It described briefly the calculation procedures required in order to obtain section properties related to each of a number of cross-section distortion modes. These properties were generally calculated using first-order theory. This paper describes in full how second-order theory can be used to calculate the section properties for all modes, including each of the four rigid body modes. In the process of developing the second-order generalized beam theory, additional section properties evolve which enable the first-order equilibrium equation to be modified to consider second-order elastic critical load problems.
TL;DR: In this paper, the model of a dynamic postbuckling behavior of a slender web is supplemented by flanges (or stiffeners) and the finite element method amended by a transformation via eigenmodes has been used.
Abstract: The model of a dynamic post-buckling behaviour of a slender web is supplemented by flanges (or stiffeners). The finite element method amended by a transformation via eigenmodes has been used. The problem of the influence of the level of the external load and the initial imperfections on the circular frequency is solved. Theoretical and numerical results are compared with results from the experiment of steel thin-walled panels loaded in compression.
TL;DR: In this paper, a simplified design method for cold-formed purlins is presented, which takes into account the lateral and torsional restraint of the purlin and the cross-section distortion.
Abstract: Cold-formed purlins have a high load carrying capacity because of their optimized cross-section and the stabilizing effect of the sheeting. The present contribution describes a simplified design method for these purlins suitable for use by practising engineers, which takes into account the lateral and torsional restraint of the purlin and the cross-section distortion. Using cross-section values determined for the whole section the stress resultants are evaluated using second-order theory, and the stresses are checked at the critical locations.
TL;DR: In this paper, a new numerical method, which allows for the exact consideration of the nonlinearities introduced in the analysis of composite beams of steel and concrete, is presented, which shows that the consideration of a simple monotone diagram may lead to dangerous conclusions regarding the safety of the beam at serviceability state.
Abstract: In the present paper a new numerical method, which allows for the exact consideration of the nonlinearities introduced in the analysis of composite beams of steel and concrete is presented. Experimental data show a nonmonotone behaviour for the load-deformation curve of the shear connectors which join the steel and the concrete. The great influence of the softening branch is demonstrated through the analysis of a slender beam spanning 30·0 m. This analysis shows that the consideration of a simple monotone diagram may lead to dangerous conclusions regarding the safety of the beam at serviceability state.
TL;DR: In this paper, the stiffness and mass matrices of complete cylindrical shells were obtained using numerical integrations by the deployment of Gauss-Legendre quadrature points, which satisfied the exact representation of rigid-body modes of displacements and all components of strains are assumed to be independent insofar as it is allowed by the compatibility equations.
Abstract: The free-vibration natural frequencies of complete cylindrical shells, having different end conditions, and cylindrical panels have been investigated. The finite element method is used in which a strain-based cylindrical shell element is employed. This element satisfies the exact representation of rigid-body modes of displacements and all components of strains are assumed to be independent insofar as it is allowed by the compatibility equations. The element has only external degrees of freedom, five at each corner node, to avoid difficulties associated with higher-order elements. The stiffness and mass matrices are obtained using numerical integrations by the deployment of Gauss-Legendre quadrature points.
TL;DR: In this paper, the authors presented the results of an experimental study on cold-formed steel columns made at the Building Research Institute of Timisoara, where the specimens were press-braked and their thickness ranged from 2 to 4 mm.
Abstract: This paper presents the results of an experimental study on cold-formed steel columns made at the Building Research Institute of Timisoara. The specimens were press-braked and their thickness ranged from 2 to 4 mm. Channel sections and lipped channel sections were tested, including columns and stub columns tests. Theoretical ultimate capacities were determined by bdAISI, ECCS and Eurocode 3—Annex A specifications. Differences between designed and experimental values for these three methods are insignificant, and theoretical results are confirmed by experimental tests for stub columns. For columns, good agreement with theoretical predictions is obtained by applying the reduction coefficients for ultimate loads given in specifications. Both for columns and stub columns, the results are more conservative for channel than for lipped channel sections.
TL;DR: In this article, an improved version of the Byskov-Hutchinson perturbation analysis is used to investigate the buckling of an elastically restrained truss structure.
Abstract: Interactive buckling of an elastically restrained truss structure is investigated by using an improved version of the Byskov-Hutchinson perturbation analysis. The mechanical model consists of two horizontal beams connected by rigid diagonals, whose out-of-plane displacements are prevented by a continuous distribution of linear springs. When the two horizontal beams are compressed, three buckling modes are possible: one overall in-plane mode and two local (lateral and torsional) modes which, for a particular choice of the geometry of the structure, may occur nearly simultaneously. Three nonlinear equilibrium equations are derived in the amplitudes of the three buckling modes and solved numerically for given initial imperfections.
TL;DR: In this article, the authors proposed a model for predicting the distinctive points observed in the response of RC membranes without tracing the load-deformation history. But the model is not suitable for the analysis of RC membrane response.
Abstract: Presented in this paper is a study to provide a practical method for predicting the distinctive points observed in the response of RC membranes without tracing the load-deformation history. Features of the proposed model, based on the solution of the governing equations derived in the secant form, include the consideration of the tension stiffening effect and multidirectional reinforcement. For practical purposes, due to simplicity of the modeling and ability to obtain the response of the RC membrane with a minimum amount of computation, the proposed method offers attractive alternatives to the use of available complicated models. The reliability of the proposed model is confirmed by comparison between predicted and test results.
TL;DR: In this paper, a study is made of the relationship between the external pressure and the buckle length for conditions representative of those involved in the arresting of a propagating buckle, and an analytical expression that defines that relationship is obtained, and its predictions are in very good agreement with those of accurate finite element solutions.
Abstract: A summary is presented of recent developments that contribute to reliably predicting the magnitude of the buckle propagation pressure for deep-water offshore pipelines. The associated problem of buckle arresting is then addressed, and a study is made of the relationship between the external pressure and the buckle length for conditions representative of those involved in the arresting of a propagating buckle. Using energy methods, an analytical expression that defines that relationship is obtained, and it is shown that its predictions are in very good agreement with those of accurate finite element solutions. The relationship between the pressure and the buckle length reported herein could be useful in improving the understanding of the forces exerted by a buckle on an arrestor during a buckle arresting process. Furthermore, an examination is made of the magnitude of the dynamic effects induced on an arrestor by a propagating buckle, and it is demonstrated that such effects are usually small.
TL;DR: In this paper, the free vibration characteristics of thin-walled ring-stiffened circular cylinders and cones were investigated using the finite element method, and comparison between theory and experiment was found to be good.
Abstract: This paper presents a theoretical and an experimental investigation into the free vibration characteristics of thin-walled ring-stiffened circular cylinders and cones. Three ring-stiffened circular cylinders and three ring-stiffened circular cones were machined from a solid mild steel shaft. For each family of vessels, the only variable was the depth of the ring stiffeners. The theoretical investigation was based on the finite element method, and comparison between theory and experiment was found to be good.
TL;DR: In this article, the authors make a contribution to the understanding of the interaction between overall lateral-torsional buckling and local buckling of a beam under transverse loading by using three approaches: numerical analysis using the asymptotic theory, a qualitative analysis using an a priori simple discrete model, and experiments.
Abstract: This paper is a contribution to the understanding of the interaction between overall lateral-torsional buckling and local buckling of a beam under transverse loading. It concentrates on the case where the critical load for local buckling is smallest. Three approaches have been used: numerical analysis using the asymptotic theory; a qualitative analysis using an a priori simple discrete model; and experiments. The study suggests that just three modes in the asymptotic analysis are adequate to describe the interactive behaviour. The resulting reduced potential energy expression is quite similar to that of the a priori simple discrete model and provides insight into the destabilizing phenomenon. The experiments confirm these results.
TL;DR: In this article, the effect of internal pressure on axial buckling (elephant foot failure) as well as the flexibility of the base ring results in noteworthy reductions of the axialbuckling resistance.
Abstract: This paper deals with practical problems encountered in the design of seismically loaded liquid-filled vertical tanks. Global stability, buckling under combined action of axial compression and internal pressure and the effect of flexible boundaries on axial buckling are studied. The question of the mutual interaction of global and local failure modes is considered. Numerical studies on the basis of finite element-discretized-shell models are carried out which show the typical features of the different failure modes. Both the effect of internal pressure on axial buckling (elephant foot failure) as well as the flexibility of the base ring results in noteworthy reductions of the axial buckling resistance. Global stability effects turned out to play no major role in the present tank design.
TL;DR: For continuous composite beams subject to increasing loads up to collapse, a very large capacity of bending moment redistribution may appear in spite of the occurrence of local buckling with a possible interaction of global buckling of a web panel in shear as discussed by the authors.
Abstract: For continuous composite beams subject to increasing loads up to collapse, a very large capacity of bending moment redistribution may appear in spite of the occurrence of local buckling with a possible interaction of global buckling of a web panel in shear. Two probative tests are presented and analysed, allowing to justify the simplified design methods adopted in Eurocode 4. An improved analysis is proposed using the concept of plastic mechanism. Also, a numerical model based on an original beam finite element is presented briefly in order developed a more general investigation in the near future.
TL;DR: In this paper, the authors describe the evolution and the present state of knowledge in the field of frames, plated structures and shells and give brief information about contributions to Session 3 of the International Conference on Coupled Instabilities in Metal Structures.
Abstract: The first part of the general report describes (i) the evolution and (ii) the present state of knowledge in the field of frames, plated structures and shells. The second part then gives brief information about contributions to Session 3 of the International Conference on Coupled Instabilities in Metal Structures.
TL;DR: In this article, a study of the large amplitude, free vibration of geometrically non-linear shallow arches is presented, where a combination of finite elements and finite difference methods is employed.
Abstract: A study of the large amplitude, free vibration of geometrically non-linear shallow arches is presented. To obtain the non-linear steady state response a combination of finite elements and finite difference methods is employed. Finite elements idealization is used to express the geometrically non-linear and incremental stiffness matrices and the rest of the terms appearing in the equation of motion are expressed by finite difference equations relating displacement, velocity and acceleration. The resulting recurrence formula is then solved by assuming that for the first time interval, the transverse displacement away from the centre of the arch, is in the form of a sinusoidal equation. The complex relationships between frequency and large amplitude for shallow arches having various ratios of radius to thickness are thus obtained and the results are discussed in relation to the elastic geometrically non-linear load-deflection curves which are generally multi valued exhibiting local maximum and minimum and resulting into snap-through between various equilibrium states. These elastic geometrically non-linear curves are based on an analytical solution in which the shape of the arch is expressed in terms of an infinite Fourier series and the thrust in the shallow arch is assumed to be constant.
TL;DR: In this paper, the buckling of a compression bar is examined like a coupled instability between the general buckling by flexural and the local bucking by plastic deformations, which corresponds to the Ayrton-Perry relationship for plastic buckling used by Maquoi and Rondal for the analytical expressions of the ECCS buckling curves.
Abstract: In the paper the author shows that plastic deformations can be considered as a bifurcational instability of the atomic lattice. Thus, the plastic buckling of a compression bar is examined like a coupled instability between the general buckling by flexural and the local buckling by plastic deformations. The modified Hunt-Burgan model is studied and an interaction relationship between the elastic buckling load and the plastic collapse load is determined. Although this relationship is obtained in an elastic field, the form corresponds to the Ayrton-Perry relationship for plastic buckling, used by Maquoi and Rondal for the analytical expressions of the ECCS buckling curves. However, one can see that the general imperfections corresponding to Eulerian buckling and local imperfection due to residual stresses have different effects, in opposition to Maquoi-Randal relationships. A new relationship for the simple plastic buckling and coupled plastic buckling are proposed.
TL;DR: In this paper, a simple two d.o.f. system is proposed to model one storey of a frame and two uncoupled critical loads which depend upon the elastic and geometric properties of the structure.
Abstract: Metal braced frames show two kinds of instability, the first related to the instability of a single beam-column pinned at its joints (Euler's problem) and the second to the side-sway of the whole frame. In this paper a simple two d.o.f. system is proposed to model one storey of a frame. It shows two uncoupled critical loads which depend upon the elastic and geometric properties of the structure. The coupled instability is considered and the different kinds of postcritical behaviour are shown. A relationship between the geometric parameters, which determines the coupled instability, is given.
TL;DR: In this paper, the free-vibration natural frequencies of an arch bridge are analyzed in terms of symmetry and anti-symmetrical modes of vibration, when the ends of the arches and decks are either hinged or fixed to rigid abutments, and the effect of varying the relative stiffnesses of the two components on the fundamental and second modes is also compared with the corresponding frequencies of the arch component vibrating on its own.
Abstract: A study of the free-vibration natural frequencies of an arch bridge is presented. The bridge consists of two structural components namely a circular arch and a flat deck, monolithically connected together at the crown of the arch. A two-dimensional mathematical model is used in the analysis; the curved component is modelled by curved-beam finite elements and the deck by straight-beam finite elements. Both symmetrical and anti-symmetrical modes of vibration are studied for such bridges when the ends of the arches and decks are either hinged or fixed to rigid abutments. The effect of varying the relative stiffnesses of the two components on the fundamental and second modes of vibration is also presented and compared with the corresponding frequencies of the arch component vibrating on its own.