Thin-walled Steel Members Research Articles

The ECBL approach for interactive buckling of thin-walled steel members

Actual buckling curves are always characterised by the erosion of ideal buckling curves. In case of compact sections this erosion is due to the imperfections, while for thin-walled members, a supplementary erosion is induced by the phenomenon of coupled instabilities. The ECBL approach- Erosion of Critical Bifurcation Load - represents a practical and convenient tool to characterise the instability behaviour of thin-walled members. The present state-of-art paper describes the theoretical background of this method and the applications to cold-formed steel sections in compression and bending. Special attention is paid to the evaluation methods of erosion coefficient and to their validation. The ECBL approach can be also used to the plastic-elastic interactive buckling of thin-walled members, and the paper provides significant results on this line.

高速移動荷重による鋼薄肉材構成板の局部振動に対する横補剛材の影響

高速移動荷重による鋼薄肉材構成板の局部振動に対する横補剛材の影響

Torsion in thin-walled cold-formed steel beams

Thin-walled cold-formed steel members have wide applications in building structures. They can be used as individual structural framing members or as panels and decks. In general, cold-formed steel beams have open sections where centroid and shear center do not coincide. When a transverse load is applied away from the shear center it causes torque. Because of the open nature of the sections, torsion induces warping in the beam. This paper summarizes the research on the behavior of cold-formed steel beams subject to torsion and bending. The attention is focused on beams subject to torque, because of the effect of transverse loads not applied at the shear center. A simple geometric nonlinear analysis method, based on satisfying equilibrium in the deformed configuration, is examined and used to predict the behavior of the beams. Simple geometric analyses, finite element analyses and finite strip analyses are performed and compared with experimental results. The influence of typical support conditions is studied and they are found to produce partial warping restraint at the ends. This effect is accounted for by introducing hypothetical springs. The magnitude of the spring stiffness is assessed for commonly used connections. Other factors that affect the behavior of cold-formed steel members, such as local buckling, are also studied.

高速移動荷重によって鋼薄肉材構成板に生じる局部振動波の特性

On the thin-walled steel members of railway bridges, it has been clarified by measuring the vibration of a railway bridge actually that local vibration of the members increases suddenly with speeding up of train. This paper aims to elucidate the mechanism of the sudden increase of the local vibration. Firstly, the phase velocity and group velocity of the local vibration in steel component plates of thin-walled steel members are computed. Secondly, the dynamic responses of the steel component plates under high speed moving loads are analyzed. The relation the local vibration with the speeding up of the moving loads are investigated on wave form, time histories, reflection and propagation of local vibration of the plates.

Recent research on stability analysis of thin-walled cold-formed steel members

Recent research on stability analysis of thin-walled cold-formed steel members

Theoretical and experimental research on web crippling of cold-formed flexural steel members

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.

Coupled instability of thin-walled members under combined bending moment, axial and shear force

In this paper we analyse the behaviour of thin-walled steel members with an I-shaped cross-section, in the presence of phenomena of coupled instability as overall-local type and combined state of stress of bending moment, axial and shear force. The analysis has been made by the ‘column model method’ and it has been used for bending moment-curvature-axial force diagrams, modified by the presence of local instability for web buckling of steel beams. The previous analysis allows one to define interaction diagrams M Imax −λ− N , which can be used to check the steel members in relation to the overall slenderness and the local slenderness of the web panel.

Web crippling strength of thin-walled steel members with web opening

This paper is concerned with the effect of web openings on the web crippling strength of unreinforced cold-formed (thin-walled) steel members. The influence of an opening has been examined through experimental research on C-shaped lipped channel sections subjected to interior one flange loading condition. First, the web crippling provisions of various Canadian design codes have been reviewed. Then, the results of the 103 laboratory tests undertaken by the authors are presented along with the description of test procedure. The parameters covered in this investigation include web height to thickness ratio, opening height/web height and opening width/bearing length. Experimental data corresponding to sections without opening have been compared to code estimations. Based on the non-linear regression analysis of the test results a prediction equation for the influence of an opening has been established. Until further results become available, the prediction equation proposed herein may be used in the web-crippling design of thin-walled steel members with web openings.

Static analysis of flexibly connected thin-walled plane frames

The static response of plane frames including nonlinear semi-rigid connection behavior, post-local-buckling strength of thin-walled steel members and first-order geometric nonlinearity is presented. Semi-rigid connection behavior is modeled using an exponential approximation of the connection flexibility-moment relationship. Post-local-buckling behavior is approximated using an effective width concept. Both axial and bending stresses are included in the direct iteration scheme used to calculate the cross section properties for the locally buckled members. Discretization of the nonlinear equilibrium equations is based on an exact elastic stiffness matrix formulation coupled with a finite element representation of first-order geometric nonlinearity. Solution of the resulting nonlinear algebraic equations is obtained using an iterative predictor-corrector strategy along with a constant spherical arc-length constraint algorithm for the automatic selection of the load step increments. Numerical results are presented for a two story, two bay frame which demonstrate the influence of flexible connections, local buckling and/or beam-column, P-delta secondary moments.

Static/Dynamic Analysis of Locally Buckled Frames

The static and dynamic behavior of plane frames composed of thinwalled steel members is presented. Frame analysis includes post‐local‐buckling and/or first‐order geometric nonlinearities. Post‐local‐buckling behavior is included using the effective width concept which includes both axial and bending stresses. Direct iteration is used to calculate the effective cross section properties for members that have locally buckled. An “exact” elastic stiffness matrix, finite element geometric stiffness, consistent mass and Rayleigh damping matrix formulation is used to discretize the dynamic equilibrium equations. The nonlinear dynamic equations are solved using a modified Newton‐Raphson iteration strategy coupled with Newmark's time integration scheme. Static and dynamic analyses of a two‐bay, two‐story frame are considered. Static problem results are presented to demonstrate the accuracy of the formulation and the influence of local buckling and/or first‐order geometric nonlinearities. Dynamic simulations are ba...

Stress Analysis of Group of Interconnected Thin-Walled Cantilevers

The longitudinal axes of the cantilevers are assumed to be parallel while the main axes of the cross sections may have arbitrary directions. In addition to rigid diaphragms the flanges of the thin-walled cantilever may be rigidly connected by an elastic continuously distributed laminar system having bending stiffness in the direction parallel to the longitudinal axes. The analytical model may be an idealization of a group of thin-walled steel members interconnected by equidistant lammelas or a group of thin-walled stiffening elements interconnected by beams in a tall building. The basic static determinate scheme will be obtained by means of fictitious longitudinal cuts along the midpoints of the laminar system and along the ridges of the thin-walled element. The unknowns are the shear force functions along the cuts, which will be obtained from compatibility conditions along the fictive cut, expressed by a system of nonhomogeneous second-order differential equations with constant coefficients.