Lateral–torsional buckling assessment of steel beams through a stiffness reduction method (original) (raw)
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Flexural–torsional buckling assessment of steel beam–columns through a stiffness reduction method
Engineering Structures, 2015
In this paper, a stiffness reduction method for the flexural-torsional buckling assessment of steel beam-columns subjected to major axis bending and axial compression is presented. The proposed method is applied by reducing the Young's E and shear G moduli through the developed stiffness reduction functions and performing Linear Buckling Analysis. To account for second-order forces induced prior to buckling, the in-plane (in the plane of bending) and out-of-plane analyses of a member are separated and stiffness reduction for the out-of-plane instability assessment is applied on the basis of member forces determined from the in-plane analysis. Since the developed stiffness reduction functions fully take into account the detrimental influence of imperfections and spread of plasticity, the proposed method does not require the use of member design equations, thus leading to practical design. For the purpose of verifying this approach, the strength predictions determined through the proposed stiffness reduction method are compared against those obtained from nonlinear finite element modelling for a large number of regular, irregular, single and multispan beam-columns.
LATERAL TORSIONAL BUCKLING RESPONSE OF STEEL BEAM WITH DIFFERENT BOUNDARY CONDITIONS AND LOADING
Strength of Materials, Vol. 46, No. 3, May,, 2014
In Eurocode 3, the general method to determine the ultimate lateral torsional buckling load of steel beams in bending is presented. This method makes use of buckling curves. The ultimate lateral torsional buckling load can also be calculated using the finite element method by means of a geometrical and material non-linear analysis on a beam including imperfections. This paper compares the ultimate loads based on the design rules in Eurocode 3 for lateral torsional buckling of laterally restrained beams in bending to the ultimate loads obtained with finite element simulations on the basis of a parameter study.
Lateral Torsional Buckling Analysis and Design of Steel Beams with Continuous Spans
2017
Design standards do not provide provisions to account for the interaction between adjacent spans of continuous beams. In the absence of such provisions, the designer may opt for calculating the lateral torsional buckling capacity for each span separately by applying the moment gradient factors provided in standards and adopting the smallest critical moment as the one governing the design. The Salvadori hypothesis of isolating a member from the rest of the structure is assessed in the present study. The elastic lateral torsional buckling resistance for continuous beams is investigated based on finite element analysis. Comparisons are made between two types of solutions: (1) those neglecting interaction effects between adjacent spans, and (2) those considering span interaction. Also examined is the effect of presence of lateral/torsional restraints at intermediate supports of continuous beams. The results illustrate the merits of adopting the FEA solution in accounting for span intera...
International Journal of Mechanical Sciences, 2011
In this paper, lateral-torsional buckling behavior of open-section thin-walled beams is investigated based on a geometrically nonlinear formulation, which considers the effects of shear deformations. A finite element numerical solution along with an incremental-iterative solution procedure is adopted to trace the pre-buckling as well as the post-buckling equilibrium paths. Formulation is applicable to a general type of open-section and load position effects are also included. Numerical results are validated through comparisons with experimental results and those based on other formulations presented in the literature. Comparisons have also been made between the results based on fully nonlinear analysis and linearized buckling analysis in order to illustrate the effects of pre-buckling deformations as well as the shear deformations on the buckling load predictions. Examples illustrate the influence of beam slenderness and moment gradient on the effects of pre-buckling deformations in predicting bucking loads.
Innovative Infrastructure Solutions
The effects of web distortion on the buckling behavior of castellated steel beams have rarely been studied; and so far, no exact formula has been proposed to predict the lateral-distortional buckling (LDB) capacity of such beams. Therefore, in the following paper, an attempt has been made to propose new formulas for predicting the LDB capacity of castellated beams using two regression models. To do this, at the first, an extensive parametric study including 480 finite element (FE) models was performed. Both material nonlinearities and initial geometric imperfections were carefully applied to the models and they were also well validated against experimental results. The next, based on the parametric study, nine non-dimensional parameters that affect the LDB behavior of castellated beams were considered, and using them as input parameters, two predictive models including stepwise regression (SR) and multiple regression (MR) were developed. The models were then used to provide new formulations for estimating the LDB strength of castellated steel beams. In the end, the proposed formulas were compared with the existing design guides available for estimating the buckling strength in AS4100, EC3, and AISC codes. The results showed that the proposed formulas for use by practical engineers are accurate enough.
Comparative Study of Lateral Torsional Buckling of Steel Beams using SAP 2000 and STAAD Pro
United International Journal for Research & Technology, 2021
When a steel beam is designed for lateral-torsional buckling, the elastic critical moment Mcr is an important design parameter. The factor that is considered for Lateral-torsional buckling is point of action of load. In this study, Double symmetric I-section, monosymmetric I-section and built-up I-section beams are considered for rotation around the minor axis and warping considering various load heights and varying degrees of end restraint. Various beam lengths and different forms of load with centric loading, beams with a channel cross-section are examined. Mcr (elastic critical moment) is determined using software and compared to values obtained using an empirical expression called the 3-factor formula in EC3 and the IS 800:2007. The disparity between the software tools under investigation is due to the different methods and assumptions used to calculate Mcr. SAP2000 and STAAD.Pro are the software tools used in this report.
2017
Lateral torsional buckling is a limit state for I-shaped steel beams that may often be a controlling issue in structural steel design. When these members are not appropriately braced so as to prevent lateral deformations and torsion, they are subjected to risk of failure by lateral torsional buckling before reaching their ultimate capacity. This paper investigates elastic lateral torsional buckling of simply supported I-shaped steel beams under concentrated load and linear moment gradient using design standards and codes, approaches from the literature and finite element analysis. Several unbraced member lengths and end moment values are taken into account to compare and evaluate these approaches in terms of elastic critical moment and end moment ratios. Analysis results show that lateral torsional buckling is a crucial stability problem for I-shaped steel members that are under flexure and it is reflected with adequate safety in the design codes and standards considering finite element analysis outcomes.
Numerical Methods in Civil Engineering, 2023
This paper uses a parametric numerical study to assess the Lateral-torsional buckling (LTB) performance of several semi-compact beams: S1, S2, and S3. The carrying capacity of these beams, predominantly loaded in bending, is approached by elastic and inelastic buckling analyses. A series of parameters that are believed to influence the resistance to LTB of class 3 beams to (EC3) steel I-beams, namely boundary conditions, flange thickness, and load application level, are investigated. An eigenvalue analysis that predicts the theoretical buckling strength through 3D computational elastic beam models is first conducted using LTBEAM software and ABAQUS. A good agreement in the prediction of Mcr was found. Then, a parametric inelastic buckling analysis is performed using the Riks method implanted in ABAQUS. Results have shown the importance of the lateral restraint conditions and the transverse stiffeners to LTB resistance of compressive flange slenderness following EC3-1-1 for cross sections with a class 3 web and class 1 or 2 flange. In addition, an interaction of local buckling (LB) and LTB in the flanges was observed exclusively for restrained beams. The applied load level strongly affects the beams' elastic and inelastic resistance to LTB.
A comparative study of beam design curves against lateral torsional buckling using AISC, EC and SP
Structural Mechanics of Engineering Constructions and Buildings
Introduction. Structural stability is an essential part of design process for steel structures and checking the overall stability is very important for the determination of the optimum steel beams section. Lateral torsional buckling (LTB) normally associated with beams subject to vertical loading, buckling out of the plane of the applied loads and it is a primary consideration in the design of steel structures, consequently it may reduce the load currying capacity. Methods. There are several national codes to verify the steel beam against LTB. All specifications have different approach for the treatment of LTB and this paper is concentrated on three different methods: America Institute of Steel Construction (AISC), Eurocode (EC) and Russian Code (SP). The attention is focused to the methods of developing LTB curves and their characteristics. Results. AISC specification identifies three regimes of buckling depending on the unbraced length of the member ( Lb ). However, EC and SP util...
DYNA
This study focused on the experimental assessment of the behavior of I-shaped steel beams with longitudinal stiffeners under the action of lateral-torsional buckling. Thirty-three IPE-140 steel beams with and without longitudinal stiffeners were tested under simple-support conditions with a laterally unbraced length ranging from 0.69 to 6.0 m. The stiffeners spacing was 0.42 m, which represented three times the depth of the section. The structural behavior of the beams is discussed in terms of their flexural capacity, the lateral displacement of the compression flange and the failure twist angle. The results showed that the use of longitudinal stiffeners increased the flexural capacity up to 82%, decreased the lateral displacement of the compression flange and the failure twist angle up to 72 and 90% respectively, with respect to the specimens without stiffeners.