Flexural–torsional buckling assessment of steel beam–columns through a stiffness reduction method (original) (raw)
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Lateral–torsional buckling assessment of steel beams through a stiffness reduction method
Journal of Constructional Steel Research, 2015
This paper presents a stiffness reduction approach utilising Linear Buckling Analysis (LBA) with developed stiffness reduction functions for the lateral-torsional buckling (LTB) assessment of steel beams. A stiffness reduction expression is developed for the LTB assessment of beams subjected to uniform bending and modified for the consideration of moment gradient effects on the development of plasticity. The proposed stiffness reduction method considers the influence of imperfections and plasticity on the response through the reduction of the Young's modulus E and shear modulus G and obviates the need of using LTB buckling curves in design. The accuracy and practicality of the method are illustrated for regular, irregular, single and multi-span beams. In all of the considered cases, the proposed method is verified against the results obtained through nonlinear finite element modelling.
Numerical analysis of local and global buckling of a stiffened beam-column
Tehnicki vjesnik - Technical Gazette
Preliminary communication The linear buckling phenomenon is obviously very important for stability of compressed supports. The determination of buckling resistance is an important characteristic of the design of steel structure. Besides, the presence of stiffeners in structural plate elements has a vital role in order to increase critical buckling load capacity. However, these stiffeners cause a redistribution in buckling behaviour in terms of local and global buckling. In this paper the transverse and longitudinal stiffeners were employed on a real beam-column structure to maximize the critical buckling loads. The objective is to find the optimum geometry of stiffeners. Based on the finite element method, a numerical model is made using the Abaqus program in order to observe the critical buckling capacity. The results showed that the local critical buckling has been significantly affected by stiffener's position in the case of transverse stiffeners, but little effect is observed on the critical local and global buckling in the case of longitudinal stiffeners.
A stiffness reduction method for the in-plane design of structural steel elements
Engineering Structures, 2014
Stiffness reduction offers a practical means of considering the detrimental influence of geometrical imperfections, residual stresses and the spread of plasticity in the analysis and design of steel structures. In this paper, a stiffness reduction approach is presented, which utilises Linear Buckling Analysis (LBA) and Geometrically Nonlinear Analysis (GNA) in conjunction with developed stiffness reduction functions for the design of columns and beamcolumns in steel frames. This approach eliminates the need for modelling geometrical imperfections and requires no member buckling checks. For columns, inelastic flexural buckling loads can be obtained using LBA with appropriate stiffness reduction, while GNA with stiffness reduction is required to determine an accurate prediction of beam-column failure. The accuracy and practicality of the proposed method is shown in several examples, including regular and irregular members. For the latter case in particular, it is found that the proposed approach provides more accurate capacity predictions than traditional design methods, when compared to results generated by means of nonlinear finite element modelling.
Finite element solutions for the buckling of columns and beams
International Journal of Mechanical Sciences, 1971
The accuracy of the finite element method in dealing with problems of the buckling of columns and beams is demonstrated by providing solutions to a variety of examples. Among the subjects included in the study are the influence of restraints and of partial plasticity of the cross-section. In all cases agreement with existing solutions is good. NOTATION B torsional stiffness of restraint C lateral stiffness of restraint E Young's modulus F intensity factor G shear modulus I minor second moment of area J torsion constant [K] stiffness matrix M~ fully plastic moment t thickness Wcr critical load F warping constant
Buckling resistance evaluation of steel beam-columns using refined General Method approach
MATEC Web of Conferences, 2019
Different aspects of Eurocode 3 General Method (GM) approaches are discussed in this paper. The purpose of present study is to improve the application of GM approach for both beam-columns without intermediate lateral-torsional restraints and with these restraints. The results from the proposed GM are compared with those from Eurocode 3-1-1 interaction equations according to Method 1 and Method 2. A better consistency between the developed GM approach and the Eurocode's interaction equation approach than Eurocode 3 GM approach is observed.
Major axis in-plane buckling resistance of I-section beam-columns under moment gradient
Routledge eBooks, 2021
The inelastic second-order resistance of I-section beam-columns under arbi trary loading cases of one-directional bending is mainly dependent upon two factors, namely the direction of bending and the contribution of the web and flanges to the section moment of inertia in the plane of bending. Based on the concept of an approximate method of the evalu ation of inelastic second-order resistance of beam-columns presented by the authors else where, the objective of the present study is to develop the model parameters representing functions for accounting an approximate inclusion of distributed plasticity effects of plastic zones (stress redistribution along the member length) and within the member most stressed section (stress redistribution across the most stressed section depth). The model parameters for major axis bending are assessed for narrow flange I-section beam-columns (symbol I is used for the narrow flange section identification) on the basis of results obtained from a number of FEM simulations based on an accurate shell modelling technique and using Abaqus software. The concept of equivalent geometric imperfections is applied in compliance with the so-called Eurocode's general method in order to include globally the effect of geomet ric and material imperfections. The resulting model parameters evaluated for I-section steel work elements being laterally and torsionally restrained are compared with those developed elsewhere for hot-rolled wide flange HEB section members subjected to both compression and bending about the major principal axis. Additionally, results are compared with those obtained in previous studies and those of Eurocodes interaction criteria based on Methods 1 and 2. Concluding remarks with regard to the in-plane buckling resistance of double-tee sec tion beam-columns are presented.
Buckling and cyclic inelastic analysis of steel tubular beam-columns
Engineering Structures, 1983
A numerical procedure combining the Fin,te Segment Method (FSM) with the Influence Coefficient Method (ICM) is presented for estimating the inelastic behaviour of steel tubular beam-columns under post-buckling and cyclic loading conditions. This combination takes the advantages of FSM and ICM, overcoming the difficulties encountered in numerical analysis at the stages of buckling and post-buckling. The effects of initial imperfections, residual stresses, and end-restraints are taken into account. Generalized stress-strain relationships are used in the analysis. Complete results obtained for a pin-ended beam-column are discussed and compared with available theoretical results
In this paper, two types of steel frames, steel frame without side sway permission and another with side sway permission are created in Abaqus with 10 multiple slenderness ratio of the columns by changing the length every time starting from 1 M and ending with 10 M length of the columns, Twenty models of steel frames with single story and single bay were created, the models are with the same 2D dimensions and material properties, the cross section of the steel is (0.5*0.5) M ,and the supports are fixed, two equal forces P= 1000 N are exerted on the frames in the position mentioned in fig 6, a beam section was defined for the frame integrated before analysis with Young modulus of elasticity E=1*10 7 N/M 2 , and shear modulus G = 3.8*106 N/M2 and poisons ratio ν = 0.3. A linear perturbation step is created for buckling and 10 eigenvalues are requested for analysis, a standard quadratic beam element type is generated with global seeding of 0.6, and 20 Jobs are created for every situation and conclusions have been obtained, the critical buckling loads of the frames fall in the ranges between the Euler loads forms which has been proved for each type of frames and this scientific approach was verified in this research, in addition to that the relation between the length of the column and the eigenvalues that represent the critical loads of buckling verified, and the simulations of the mode shapes of buckling of the steel frames were identified adopting finite element analysis which shows the amount of loads necessary to reach each mode shape of buckling for each type of steel frames mentioned before .
Out-of-plane buckling resistance of rolled steel H-section beam-columns under unequal end moments
Journal of Constructional Steel Research, 2019
A novel analytical model is proposed for establishing design criteria based on the decomposition of the in-plane deformation and out-of-plane stability states. First part of this study considered the in-plane buckling resistance of beam-columns. This study uses the results from Gizejowski et al. [42] to develop an analytical model for the inelastic out-of-plane buckling resistance of beam-columns subjected to a moment gradient. The elastic flexural-torsional buckling solution is combined with the in-plane solution via the generalised Ayrton-Perry model. In order to unify the recommendations for the resistance evaluation of beams, columns, and beamcolumns, the model is customised to conform to the standard Eurocode technique of modelling buckling resistance of steel elements in compression or bending about the cross-sectional axis with the greater moment of inertia. As a result, the out-of-plane resistance interaction curves, expressed in dimensionless coordinates, which describe the beam-column flexural-torsional buckling resistance and consider lateral-torsional buckling effects, are obtained. The results of finite element simulations are used for the verification of the developed analytical formulation. Two numerical techniques of imperfection modelling are used: an equivalent geometric imperfection approach with the Maquoi-Rondal generalised initial imperfection and an approach that individually considers geometric and material imperfections. The results obtained from the proposed analytical model and those obtained using the Eurocode design criteria and other recent analytical proposals are compared. Finally, concluding remarks and directions of future studies are also presented.
Lateral buckling of thin-walled beam-column elements under combined axial and bending loads
Based on a non-linear stability model, analytical solutions are derived for simply supported beam-column elements with bi-symmetric I sections under combined bending and axial forces. An unique compact closed-form is used for some representative load cases needed in design. It includes first-order bending distribution, load height level, pre-buckling deflection effects and presence of axial loads. The proposed solutions are validated by recourse to non-linear FEM software where shell elements are used in mesh process. The agreement of the proposed solutions with bifurcations observed on non-linear equilibrium paths is good. It is proved that classical linear stability solutions underestimate the real resistance of such element in lateral buckling stability especially for I section with large flanges. Numerical study of incidence of axial forces on lateral buckling resistance of redundant beams is carried out. When axial displacements of a beam are prevented important tension axial forces are generated in the beam. This results in important reduction of displacements and for some sections, the beam behaviour becomes non-linear without any bifurcation. r