Showing papers in "Thin-walled Structures in 1990"
TL;DR: In this article, an approximate method for determining the range of load oscillations and load-deflection behavior of axially crushed round stocky tubes which deform in an axisymmetric mode is developed.
Abstract: An approximate method for determining the range of load oscillations and load-deflection behaviour of axially crushed round stocky tubes which deform in an axisymmetric mode is developed. Theoretical estimates based on different kinematic models are compared with each other and with experimental observations. Results indicate that the effects of axial and hoop stresses, imperfection sensitivity, strain-hardening and hinge curvature, should be considered in the analysis if the tube's behaviour is to be predicted accurately.
80 citations
TL;DR: In this paper, the authors compared a theoretical method for predicting the inelastic distortional buckling strength of thin-walled columns with column tests, based on a spline finite strip buckling analysis which takes into account the nonlinear stress-strain behaviour of the steel making up the test sections, and the fix-ended test conditions.
Abstract: Thin-walled channel sections may buckle in a distortional mode when subjected to compression. A variety of cold-formed channel columns were tested recently to study distortional buckling in the inelastic range. This paper describes a comparison of a theoretical method for predicting the inelastic distortional buckling strengths of thin-walled columns with the column tests. The method is based on a spline finite strip buckling analysis which takes into account the non-linear stress-strain behaviour of the steel making up the test sections, and the fix-ended test conditions. The inelastic buckling analysis is found to produce accurate estimates of the test failure loads and failure modes
52 citations
TL;DR: In this paper, a unified approach is presented for the analysis of the shear strain effects in thin-walled beams subjected to both non-uniform bending and torsion, and a suitable axial displacement field is introduced by making the basic choice that the solution to the St. Venant problems is to be reproduced for v = 0.
Abstract: In this study a unified approach is presented for the analysis of the shear strain effects in thin-walled beams subjected to both non-uniform bending and torsion. Middle surface shear strains are taken into account for open as well as closed cross-sections. A suitable axial displacement field is introduced by making the basic choice that the solution to the St. Venant problems is to be reproduced for v = 0 . By making use of a variational formulation, a system of differential equations is derived which rules the behaviour of a thin-walled beam with any cross-section. Hence the influence of the shear strains on the stress state as well as on the global deformation of the beam is shown through some significant examples.
50 citations
TL;DR: In this paper, the axial impact of cylindrical tubes, which incorporate axial stiffeners, is examined and the effect of placing the stiffeners externally or internally is examined.
Abstract: The axial impact of cylindrical tubes, which incorporate axial stiffeners, is examined in this paper. For comparison purposes, the effect of static loading is also studied. An examination is made into the influence of stiffener depth (T), number of stiffeners (N) and the effect of placing the stiffeners externally or internally. The experimental results on mild steel specimens show that there are considerable differences between the static and dynamic modes of failure, and that an optimum T/D ratio may exist for a given value of N.
40 citations
TL;DR: In this article, the authors describe recent work performed at the University of Sydney to develop buckling and nonlinear analyses of thin-walled structural members undergoing local, distortional and overall buckling.
Abstract: This paper describes recent work performed at the University of Sydney to develop buckling and nonlinear analyses of thin-walled structural members undergoing local, distortional and overall buckling. The analyses are based on the finite strip method of structural analysis and include elastic and inelastic buckling and the full nonlinear response with both post-local buckling and plasticity. Two variations of the finite strip method have been used, these being the semi-analytical and spline finite strip methods. A nonlinear beam-column analysis based on the influence coefficient method for including the local buckling behaviour in the overall member response is also described. The analytical methods are compared with tests performed at the University of Sydney on cold-formed rectangular hollow sections, welded I-sections, welded channel sections and cold-formed channel sections. Spatial plastic collapse mechanismsdeveloped for the welded sections described above are also compared with the post-ultimate response of the test sections.
36 citations
TL;DR: In this paper, the theoretical and experimental behavior of box-columns of varying b/t ratios under loadings of axial compression and torsion and their combinations is described.
Abstract: This paper describes a study of the theoretical and experimental behaviour of box-columns of varying b/t ratios under loadings of axial compression and torsion and their combinations. Details of the testing rigs and the testing methods, the results obtained such as the load-deflection curves and the interaction diagrams, and experimental observations regarding the behaviour of box-models and the types of local plastic mechanisms associated with each type of loading are presented. A simplified rigid-plastic analysis is carried out to study the collapse behaviour of box-columns under these loadings, based on the observed plastic mechanisms, and the results are compared with those of experiments.
27 citations
TL;DR: In this article, a detailed treatment of the non-linear elastic biaxial bending and torsion of thin-walled open section members is presented, and the treatment is valid for uniform members of linear elastic material, and is limited to small strains and rotations, and moderate deflections.
Abstract: This paper presents a detailed treatment of the non-linear elastic biaxial bending and torsion of thin-walled open section members. The treatment is valid for uniform members of linear elastic material, and is limited to small strains and rotations, and moderate deflections. Shear straining of the mid-surface of the member wall is neglected, and it is assumed that the member does not distort or buckle locally. The effects of initial deformations, loads, stresses, and strains are incorporated. The treatment is based on non-linear strain-displacement relationships, and these are used to derive the non-linear equilibrium and tangent stiffness equations in forms which are suitable for computer solution by the finite element method. Approximate linear and non-linear differential equilibrium equations are derived, as are the differential equilibrium equations and the energy equation for neutral equilibrium at bifurcation buckling, and these are then related to the classical equations developed by Timoshenko, Vlasov, and others.
19 citations
TL;DR: In this article, the buckling behavior of thin-walled beams with an enforced axis of rotation subjected to longitudinal compressive loadings was modeled by a refined nonlinear beam theory and an analytical solution was obtained to the beam buckling equations.
Abstract: The subject of this paper is the buckling behavior of thin-walled beams with an enforced axis of rotation subjected to longitudinal compressive loadings. The stiffeners are mathematically modeled by a refined nonlinear beam theory recently derived. An analytical solution is obtained to the beam buckling equations. This solution is expressed in terms of a simple formula which yields the tripping loads of T, angle, I, Z, and other open cross-sections. These predictions are shown to agree with those of other authors and with a finite element code.
19 citations
TL;DR: In this article, a fine element method that incorporates plate behavior is developed for modeling the lateral-distortional buckling of tee-section beams, which is shown to agree well with independent buckling results for tee-beams.
Abstract: A fine element method that incorporates plate behaviour is developed for modelling the lateral-distortional buckling of tee-section beams. The method is shown to agree well with independent buckling results for tee-beams. Since relatively few elements are needed to obtain satisfactory convergence, the method is efficient computationally. The finite element analysis is used to study the elastic distortional buckling of tee-beams of practical geometry under moment gradient. The disparities found between the elastic flexural-torsional and distortional buckling moments are discussed.
18 citations
TL;DR: In this paper, the bending coefficient is introduced and a new formulation of the shear coefficient is given for thin-walled prismatic girders based on equivalence of natural frequencies of simply supported Girders and their beam idealizations.
Abstract: The bending coefficient is introduced and a new formulation of the shear coefficient is given for thin-walled prismatic girders based on equivalence of natural frequencies of simply supported girders and their beam idealizations. Analytical and numerical procedures are developed and their application is illustrated. Formulae for natural frequencies and stiffness coefficients for some girders of simple cross-sections are tabulated.
17 citations
TL;DR: In this paper, a non-dimensional equation for the elastic lateral buckling load of straight prismatic beams of monosymmetric cross-section with general boundary conditions and general loading, which includes the effects of initial bending curvature prior to buckling, is derived.
Abstract: A new approximate non-dimensional equation for the elastic lateral buckling load of straight prismatic beams of monosymmetric cross-section with general boundary conditions and general loading, which includes the effects of initial bending curvature prior to buckling, is derived. For sections where the flexural rigidity about the axis of initial bending, EIzz, is smaller than the flexural rigidity about the other principal centroidal axis, EIyy, it is shown that lateral buckling is still a possibility
TL;DR: In this article, thin-walled square tubes of aluminium and mild steel were subjected to lateral compression between two opposing wedge-shaped and flat-faced indenters of narrow width, in an Instron machine.
Abstract: Thin-walled square tubes of aluminium and mild steel were subjected to lateral compression between two opposing wedge-shaped and flat-faced indenters of narrow width, in an Instron machine. Typical histories of their deformation, load-compression response and the energy absorbed during collapse are discussed. An analysis based on the formation of plastic hinges is presented to describe the geometry changes and collapse behaviour of the tubes and the results obtained thereby are compared with the experiments.
TL;DR: In this article, a decision support system (DSS) was developed on a personal computer for the economic design of steel structures, which contains six various-type single-criterion and seven multicriteria optimization methods.
Abstract: A decision support system (DSS) was developed on a personal computer for the economic design of steel structures. The DSS contains six various-type single-criterion and seven multicriteria optimization methods. The economic design of the asymmetric main box girders of overhead travelling cranes was realized by considering four objective functions and sixteen nonlinear inequality constraints according to BS 2573 and BS 5400. Constraints on static and fatigue stress, on local buckling of flange and web plates, as well as on static deflection, are considered. Numerical computations show the effects of material, welding, surface preparation and total cost on each other. Use of higher strength steel may result in savings on the cost of materials, depending on the cost factor employed.
TL;DR: In this article, two simple models which complement one another in mirroring the plastic buckling properties of structures are analysed in detail to introduce a scheme for postbuckling and imperfection sensitivity analysis that is suitable for tackling real structures.
Abstract: In this paper, two simple models which complement one another in mirroring the plastic buckling properties of structures are analysed in detail to introduce a scheme for postbuckling and imperfection sensitivity analysis that is suitable for tackling real structures. The variation of the size of the unloading area is used as the perturbation parameter and a special perturbation scheme is designed to deal with the moving boundary problems caused by plastic unloading, so that the extension of Koiter's theory of initial elastic postbuckling to the plastic range becomes possible.
TL;DR: In this article, a study of rectangular cross-section thin-walled beams under torsional, distortional and bimomental loads is presented and a closed form solution is given with reference to the matrix form of the governing differential system together with a discussion of a sixth-order "uncoupled" differential equation generalizing the BEF analogy.
Abstract: A study of rectangular cross-section thin-walled beams under torsional, distortional and bimomental loads is presented. The assumed displacement field describes both torsional and distorsional behaviour, the shearing strain in the walls being taken into account. By a variational principle the equilibrium and boundary equations are derived and a physical interpretation of the natural conditions is given. A closed form solution is given with reference to the matrix form of the governing differential system together with a discussion of a sixth-order ‘uncoupled’ differential equation generalizing the BEF analogy. The present formulation shows that, in general, torsion and distortion are pair of coupled problems and a study of distortion without considering torsion would therefore not be legitimate. The comparison of the results predicted by the theory is in good agreement with experimental evidence.
TL;DR: In this paper, the authors extend the thin plate theory to the analysis of non-prismatic space structures, where the plates that form the space structures are treated as flat shells and the Mindlin plate theory is adopted to model the bending action of the plate.
Abstract: The spline finite strip based on the thin plate theory has been demonstrated to be a versatile tool for the analysis of plates and shells. Applications of this method to the analysis of prismatic space structures have also been reported. This paper attempts to extend the method to the analysis of non-prismatic space structures. In the analysis, the plates that form the space structures are treated as flat shells. The Mindlin plate theory is adopted to model the bending action of the plate, and the in-plane action is modelled in the usual manner. The present formulation, which requires only C° continuity for the displacement interpolation functions, allows greater flexibility in the geometry of the structures. The accuracy and versatility of the method are also demonstrated by numerical examples.
TL;DR: In this article, a practical method for the analysis and design of roof Z-purlins is described and a practical design example is included, which is idealized to behave in a manner analogous to a stiffened plate in evaluating the section properties and allowable bending stresses.
Abstract: The lack of a useful and efficient analysis and design method is a hindrance to the widespread acceptance of cold-formed structural steel members as roof purlins in conventionally engineered buildings. This paper outlines a practical method for the analysis and design of roof Z-purlins. The details used in formulation of the design method are described and a practical design example is included. The roofing system is idealized to behave in a manner analogous to a stiffened plate in evaluating the section properties and allowable bending stresses. This idealization is considered appropriate as the roof system is composed of Z-purlins which are supported at intervals by structural framing and has roof decking attached continously to the outer flange. The roof decking is corrugated and serves as diaphragm bracing for the condition of flexural bending of the Z-purlin. The section properties are considered based upon a composite section, the Z-purlin and deck. In evaluating the allowable bending stress, F b , the top flange of the Z-purlin is considered to be fully braced by the roof deck whereas the bottom flange is considered to be unbraced except at supporting frames and interior inflection points.
TL;DR: The stability analysis of stiffened plates by means of the finite strip method is presented in this article, which is based on the thin shallow theory, giving nonlinear strain displacement relations, but linear curvature displacement relations.
Abstract: The stability analysis of stiffened plates by means of the finite strip method is presented. The studies are based on the thin shallow theory, giving nonlinear strain displacement relations, but linear curvature displacement relations. The nonlinear equilibrium equations are obtained by the principle of incremental virtual work, using finite strip discretization. The higher order strip with one internal nodal line is applied. It is shown that considerable improvements can be obtained using this kind of strip. It is especially true for the postbuckling analysis. Numerical examples of the strength of stiffened plates in compression are carried out, covering a range of plate and stiffener slenderness.
TL;DR: In this article, the effect of shear lag on the elastic behaviour of box girders is addressed and simple design rules for estimating its influence are described, which are derived from the results of recent research and their impact on the new generation of limit state codes.
Abstract: This paper presents a comprehensive guide to designers for dealing with the shear lag problem in structural design. First, the effect of shear lag on the elastic behaviour of box girders is addressed and simple design rules for estimating its influence are described. The second part of the paper describes design methods for assessing the effect of shear lag at the ultimate limit state. These are derived from the results of recent research and their impact on the new generation of limit state codes is examined. The paper provides a compact reference of practical design methods and a bibliography of the associated research. It also forms the background to the design rules in EC3 Part 2 (Bridges).
TL;DR: In this article, the authors discuss the general design principles which are used to achieve exciting, visual and technologically intriguing forms with such high slenderness ratios, i.e., membrane roof structures may behave satisfactorily with ratios of up to 50 000 and thus might be termed the "ultimate thin-walled structure".
Abstract: Whilst for normal thin-gauge materials such as steel and aluminium, buckling is a problem when the ratio of unsupported width to thickness is perhaps in the order of 200 or so, membrane roof structures may behave satisfactorily with ratios of up to 50 000 and thus might be termed the ‘ultimate thin-walled structure’. All modern architectural membrane structures are prestressed to maintain a tensile state and to reduce deflections under applied loadings such as from wind. These forms of ‘soft shells’ are in two broad categories — the air-supported type and the tension type. This paper discusses the general design principles which are used to achieve exciting, visual and technologically intriguing forms with such high slenderness ratios.
TL;DR: In this article, the buckling of a circular cylinder subjected to a set of equally distributed discrete axial concentrated loads is studied and it is shown that the critical load of a cylinder under axial compression is very sensitive to imperfection of the applied loads as well as to initial geometric imperfections and the boundary conditions.
Abstract: An important phenomenon is presented which has not been given sufficient attention in the stability of shell structures: the buckling of a circular cylinder subjected to a set of equally distributed discrete axial concentrated loads is studied. It is shown that the critical load of a circular cylinder under axial compression is very sensitive to imperfection of the applied loads as well as to initial geometric imperfections and the boundary conditions.
TL;DR: In this paper, an inelastic method of analysis of the distortional buckling of monosymmetric I-beams is augmented to include the effects of elastic restraints against translation, minor axis rotation, torsion and warping.
Abstract: An inelastic method of analysis of the distortional buckling of monosymmetric I-beams is augmented to include the effects of elastic restraints against translation, minor axis rotation, torsion and warping The method is validated for problems for which inelastic, distortional and restraint solutions are known A study is made of a monosymmetric beam with separate translational, rotational and torsional restraints, and conclusions are made regarding the strength of the beam when the cross-section is free to distort
TL;DR: In this paper, it was shown that the moment-curvature relationship can only develop over a finite length associated with the half-wavelength of the final plastic buckle, and that it cannot develop over an infinitesimal length.
Abstract: The nonlinear moment-curvature relationship of thin-walled beams, due to a combination of non-Hookean material behaviour and local buckling, inevitably leads to a ‘strain-softening’ component after a peak has been reached. Representation of this relationship in continuum mechanics leads to fallacious estimates of the static or incremental collapse load capacity of continuous beams. More realistic results are obtained when it is recognised that the moment-curvature relationship can only develop over a finite length associated with the half-wavelength of the final plastic buckle. It cannot develop over an infinitesimal length.
TL;DR: In this article, specific methods for optimal design of thin-walled structures and with the problem of optimal design for serviceability and ultimate limit state are discussed, and specific solution techniques which have been found to be suited for structural optimization and selected applications are presented.
Abstract: The present paper deals with specific methods for optimal design of thin-walled structures and with the problem of optimal design for serviceability and ultimate limit state. A brief classification of structural optimization is given first, followed by a general formulation of the optimal design problem for thin-walled structures and by a discussion of the design models involved. Specific solution techniques which have been found to be suited for structural optimization and selected applications are presented.
TL;DR: In this paper, the use of bubble elements in buckling analysis is examined, taking frame elements as a starting point, and two formulations are presented, and the greatly improved performance of these formulations is demonstrated.
Abstract: Bubble functions are finite element modes that are located entirely within a single element. Elements with such modes have an added complexity, and are generally not favoured in linear analysis. This is because the extra element complexity is not rewarded with a commensurate improvement in performance. The use of bubble elements in buckling analysis is examined, taking frame elements as a starting point. Two formulations are presented, and the greatly improved performance of these is demonstrated. The results indicate that the efficiency of bubble formulations needs to be re-thought.
TL;DR: In this article, an elastic folded palte method of analysis has been applied to model the behavior of composite floor decks constructed with profiled steel sheeting acting as formwork and reinforcement to a concrete slab.
Abstract: Composite floor decks constructed with profiled steel sheeting acting as formwork and reinforcement to a concrete slab are increasing in popularity. In this paper an elastic folded palte method of analysis has been applied to model their behaviour. The analytical model idealises both the steel sheeting and the concrete as a collection of thin-walled plates and separates the bending and shear action between horizontal and vertical elements. The effects of concrete in tension and slip between the concrete and steel have been included. The method has been used to analyse the results of 32-full-scale slab tests and is found to give good results.
TL;DR: In this paper, the second of two articles devoted to the study of spherical tanks filled to capacity with liquid, the analytical expressions derived earlier are used to conduct a comprehensive parametric investigation of their structural response, espicially as regards the bending disturbances in the region of the vertical supports.
Abstract: In this, the second of two articles devoted to the study of spherical tanks filled to capacity with liquid, the analytical expressions derived earlier are used to conduct a comprehensive parametric investigation of their structural response, espicially as regards the bending disturbances in the region of the vertical supports. The relative importance of these bending effects (both in magnitude and in extent) is illustrated by comparing the total stresses with their membrane counterparts for several typical liquid containers which cover the practical range of radius-to-thickness ratios.
TL;DR: In this article, a theoretical analysis of the transverse stresses in the flanges of a simply supported box girder, under a symmetrical static concentrated load acting at the mid-span, is conducted using the finite element technique.
Abstract: A theoretical investigation into the transverse stresses in the flanges of a simply supported box girder, under a symmetrical static concentrated load acting at the mid-span, is conducted using the finite element technique. Substantial membrane transverse stresses are detected. An explanation of this phenomenon is presented. The explanation is investigated by dividing the box girder into two identical channels. A torque is introduced by virtue of the central load being offset transversely with respect to the shear centre of each channel, and hence membrane transverse stresses are induced. In order to verify the above allocation of cause to consequence, certain lines of enquiry in connection with the behaviour of open and closed thin-walled girders are pursued. Correlation between the results revealed by the finite element analysis and those determined using simple structural mechanics principles is indicated.
TL;DR: In this paper, the interaction equations for biaxially loaded angle sections are presented and lower and upper bound solutions are also given for the case of bending combined with torsion.
Abstract: Interaction equations for biaxially loaded angle sections are presented in this paper. Lower and upper bound solutions were also given for the case of bending combined with torsion.