Cold-formed Thin-walled Beams Research Articles

Study on the flexural behavior of corroded built-up cold-formed thin-walled steel beams

Eight cold-formed thin-walled steel beams were performed to investigate the effect of corrosion damage on the flexural behavior of steel beams. The relationships between failure modes or load-displacement curves and corrosion degree of steel beams were investigated. A series of parametric analysis with more than forty finite element models were also performed with different corrosion degrees, types and locations. The results showed that the reduction of cross-section thickness as well as corrosion pits on the surface would lead to a decline in the stiffness and flexural capacity of steel beams, and gradually intensified with the corrosion degree. The yield load, ultimate load and critical buckling load of the corroded specimen IV-B46-4 decreased by 22.2%, 26% and 45%, respectively. The failure modes of steel beams changed from strength failure to stability failure or brittle fracture with the corrosion degree increasing. In addition, thickness damage and corrosion pits at different locations caused the degradation of flexural capacity, the worst of which was the thickness damage of compression zone. Finally, the method for calculating flexural capacity of corroded cold-formed thin-walled steel beams was also proposed based on experimental investigation and numerical analysis results.

The Numerical Investigation of Thin-Walled Beams with Modified C-Sections

Abstract Demand for thin-walled structures has been increasing for many years. Cold- formed, thin-walled channel beams are the subject of presented research. The local elastic buckling and limit load of these beams subjected to pure bending are investigated. This study includes numerical investigation called the Finite Strip Method (FSM). The presented results give a deep insight into behaviour of such beams and may be used to validate analytical models. The number of works devoted to the theory of thin-walled structures has been steadily growing in recent years. It means that is an increasing interest in practical methods of manufacturing cold-formed thin-walled beams with complicated cross-sections, including also beams with web stiffeners. The ratio of transverse dimensions of beam to its wall-thickness is high, therefore, thin-walled beams are prone to local buckling that may interact with other buckling modes. The stability constraints should be always considered when using cold-formed thin-walled beams.

Selected local stability problems of channel section flanges made of aluminium alloys

The paper addresses the issue of local buckling of compressed flanges of cold-formed thin-walled channel columns and beams with nonstandard flanges composed of aluminium alloys. The material behaviour follows the Ramberg–Osgood law. It should be noted that the proposed solution may be also applied for other materials, for example: stainless steel, carbon steel. The paper is motivated by an increasing interest in nonstandard cold-formed section shaping in local buckling analysis problems. Furthermore, attention is paid to the impact of material characteristics on buckling stresses in a nonlinear domain. The objective of the paper is to propose a finite element method (FEM) model and a relevant numerical procedure in ABAQUS, complemented by an analytical one. It should be noted that the proposed FEM energetic technique makes it possible to compute accurately the critical buckling stresses. The suggested numerical method is intended to accurately follow the entire structural equilibrium path under an active load in elastic and inelastic ranges. The paper is also focused on correct modelling of interactions between sheets of cross section of a possible contact during buckling analysis. Furthermore, the FEM results are compared with the analytical solution. Numerical examples confirm the validity of the proposed FEM procedures and the closed-form analytical solutions. Finally, a brief research summary is presented and the results are discussed further on.

Limit load of cold formed thin-walled nonstandard channel beams

Cold-formed thin-walled beams may lose the stability in different ways. The common buckling modes which have an influence on the failure of the beam are lateral-torsional, local and distortional buckling. The strength of cold-formed members can be calculated with the EffectiveWidth Method which is incorporated in many international and national standards. In this paper, the experimental and theoretical results calculated with the aforementioned method have been compared.

Effective Shaping of Cold-Formed Thin-Walled Built-up Beams in Pure Bending

Cold-formed thin-walled beams with an open cross section are widely used in different branches of industry. They tend to buckle in a variety of modes, which can be described as local, distortional, lateral-torsional buckling and bending. In this paper, the investigation on built-up I-sections, formed by assembling the stiffened cold-formed channel sections, with or without edge stiffener is presented. Parametric studies are carried out for five different section geometries with 16 specimens, tested under two point loading, to identify factors affecting the flexural strength of stiffened cold-formed steel built-up sections. The section geometries are chosen such that all types of buckling modes are met with. Critical load obtained from experiments is compared with finite element analysis results. Finally, it discusses the suitability of the current design methods (American Iron and Steel Institute) and provides design recommendations for stiffened cold-formed built-up sections.

Study of Mechanical Property of Cold-Formed Thin-Walled Steel Lightweight Concrete Composite Floor

For analysis of mechanical property and bearing mechanism of the composite floor consisting of cold-formed thin-walled steel beams and lightweight aggregate concrete panels, the static load test of a composite floor was presented. The floor specimen is simply supported at the two shorter sides of it and the other two sides free. The equivalent uniform loads are applied to the floor through piling up the load blocks on the supper surface of the floor. The displacements of the floor and strains of specimens were measured and analyzed. It is denoted that the vertical displacements of the floor varied linearly with the load while it is less than 8kN, but the slips of main beam and concrete panel vary nonlinearly during the whole loading process. It was seen that there were not evident cracks in the concrete panels while the applied loads are much larger than the normal loads.

Multicriteria optimization of cold-formed thin-walled beams with generalized open shape under different loads

The paper presents an analysis of the optimal design of cold-formed beams with generalized open shapes under pure bending, uniformly distributed loads, concentrated loads and axial loads with constant bending moment. The optimization problem includes the cross section area as the first objective function and the deflection of a beam as the second one. The geometric parameters of cross sections are selected as design variables. The set of constraints includes global stability condition, selected forms of local stability conditions, strength condition and technological and constructional requirements in a form of geometric relations. The strength and stability conditions are formulated and analytically solved using mathematical equations. The optimization problem is formulated and solved with help of the Pareto concept of optimality. The numerical procedure, based on the Messac normalized constraint method, include discrete, continuous and discrete-continuous sets of design variables. Results of the numerical analysis for different loads of beams with monosymmetrical cross section shapes are presented in tables.

Distortional Buckling of Cold-Formed Thin-Walled Channel Beams in Combined Compression and Minor Axis Bending

On the basis of the Generalized Beam Theory (GBT), this paper presents an elastic analysis of the distortional critical stress of cold-formed thin-walled lipped channels in combined compression and minor axis bending. The results obtained using the exact analysis presented herein have shown excellent agreement with previous available results. And the accuracy, validity and effectiveness of the presented solution were demonstrated. The calculating process was displayed by an example which can give reference to the research and design. This paper will contribute to the understanding of distortional mechanics in thin-walled members.

Buckling and optimal design of cold-formed thin-walled beams: Review of selected problems

The paper is devoted to cold-formed thin-walled channel beams with open or closed flanges. The global–local buckling and optimization of these beams are described. The review includes simple analytical description and calculations, numerical analysis, and the laboratory tests of selected beams. The buckling problems for flanges and webs of thin-walled beams are described in detail. Additionally, an objective comparison of the beams of different cross sections is presented. A quality measure of thin-walled beams is proposed. Comparison of selected thin-walled beams with use of the quality measure is presented in figures.

Elastic Buckling of Cold-Formed Thin-Walled Channel Beams with Drop Flanges

The subject of the paper is cold-formed thin-walled channel beams with open or closed profile of drop flanges. The geometric properties of two C-sections are described including warping functions and warping inertia moments. The analytical solutions of problems of global and local stability of thin-walled beams are presented. The theoretical solutions of elastic buckling problems of these beams are numerically found using FEM and are experimentally verified. The results of analytical and numerical investigations are compared and presented in the tables and figures.

Experimental investigations of buckling of lipped, cold-formed thin-walled beams with I-section

Cold-formed thin-walled beams with open cross-sections are widely used in different branches of industry. They tend to buckle locally because of the shapes of their cross-sections. In this paper, the results of experimental investigations of lipped I-section beams are presented. The beams have been loaded with bending moments and a concentrated force. The experimental values of critical load are compared with those obtained with the help of FEM and theoretical analyses.

Bicriteria optimization of cold-formed thin-walled beams with monosymmetrical open cross sections under pure bending

This work deals with the problem of optimal design of selected channel section shapes under bending moment. The optimization problem is given as the bicriteria one, where the cross-sectional area of the thin-walled beam is the first objective function, while the deflection of the beam is the second one. The geometric parameters of cross section were selected as design variables. The set of constraints includes global and local stability conditions, the strength condition, and technological and constructional requirements in the form of geometric relations. The optimization problem was formulated and solved with the help of the Pareto concept of optimality and preference functions. The numerical procedures include discrete, continuous and discrete–continuous sets of the design variables. Results of numerical analysis are presented in the form of tables, cross section outlines and diagrams. At the end of the work, the results are discussed and the directions of further research are provided.

Bicriteria optimal design of open cross sections of cold-formed thin-walled beams

This paper presents a analysis of the problem of optimal design of the beams with two I-type cross section shapes. These types of beams are simply supported and subject to pure bending. The strength and stability conditions were formulated and analytically solved in the form of mathematical equations. Both global and selected types of local stability forms were taken into account. The optimization problem was defined as bicriteria. The cross section area of the beam is the first objective function, while the deflection of the beam is the second. The geometric parameters of cross section were selected as the design variables. The set of constraints includes global and local stability conditions, the strength condition, and technological and constructional requirements in the form of geometric relations. The optimization problem was formulated and solved with the help of the Pareto concept of optimality. During the numerical calculations a set of optimal compromise solutions was generated. The numerical procedures include discrete and continuous sets of the design variables. Results of numerical analysis are presented in the form of tables, cross section outlines and diagrams. Results are discussed at the end of the work. These results may be useful for designers in optimal designing of thin-walled beams, increasing information required in the decision-making procedure.

Bicriterion Optimization of Cold‐Formed Thin‐Walled Beams

AbstractBicriterion optimization of cold‐formed thin‐walled beams is presented in this paper. Simply supported beams with the crosssection similar to I‐section are considered. They are loaded with bending moments on both ends. The area of the cross section and relative maximum deflection are optimization criteria. The geometrical, strength and stability constraints are taken into account during the optimization process. The results of an example problem are presented in the form of tables. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Optimization of mono- and anti-symmetrical I-sections of cold-formed thin-walled beams

Subject of the study includes mono- and anti-symmetrical open I-sections of cold-formed thin-walled beams with double flanges. The beams under uniformly distributed vertical load are simply supported at both ends. Geometric properties of each of the I-sections are separately described by dimensionless parameters. Strength, global and local buckling conditions are defined for these beams. A dimensionless objective function is assumed and formulated on the grounds of the optimization criterion. Numerical study of a family of thin-walled beams is carried out. Results of the study are presented graphically.

Optimization of open cross section of the thin-walled beam with flat web and circular flange

This paper is devoted to cold-formed thin-walled beams with open cross section. The beam cross section is optimized for a fixed cross section area under strength and stability constraints. Optimal geometrical parameters of the cross section are determined with regard to maximal and safe bending moment. The strength condition is a classical condition applied to the theory of beams for assumed allowable stress. The stability condition serves also as a classical condition for lateral buckling, taking the warping torsion into account. Moreover, the thin-walled beams have been analyzed, for which the shear center, i.e. the main pole, is located in the centroid of the cross section. Results of the numerical analysis are given. Figures present examples of optimal cross sections of the thin-walled beams.