Generalized Elastic Lateral-Torsional Buckling of Steel Beams

Lateral-torsional buckling of unrestrained steel beams under fire conditions: improvement of EC3 proposal

A concise review is provided of the classical elastic lateral-torsional buckling moment for steel beams as utilized in the AISC Specification (2022). Rather than make assumptions regarding the cross-section properties, the derivation is provided in its general form for an arbitrary steel beam—that is, one that may be asymmetric and may include any manner of varying geometry, thickness, or cross-section shape. The cross-section properties that underpin the calculation are fully detailed. The assumptions that are inherent in the classical derivations (no shear, no cross-section distortion, etc.) are also fully detailed. The manner in which the generalized lateral-torsional buckling formula may be simplified for particular sections (e.g., a singly symmetric channel) with no loss of accuracy is explained. Adaptations and approximations utilized in the 2022 edition of the AISC Specification for elastic lateral-torsional buckling moment of specific sections (e.g., mono-symmetric I-section, angles, etc.) are assessed against the actual elastic solution, and the accuracy and clarity of the assumptions utilized are evaluated. The generalized formula, consistent with current assumptions but applicable to all structural steel cross sections, is recommended for future reference in the main body of the AISC Specification.

Experimental and numerical investigation on flexural-torsional buckling of Q460 steel beams

Reliability and lateral buckling of thin-walled steel beams have become major concerns among researchers in civil engineering. A comparative study on the reliability of these beams has been conducted, focusing on the effects of lateral-torsional buckling (LTB) in both linear and non-linear domains. Initially, a non-linear model is applied within the context of large torsion using non-linear kinematics. Galerkin's method is utilized to derive equilibrium equations for simply supported beams, and numerical solutions are obtained using the Arc-length method. Theoretical and numerical results are examined for bi-symmetric I-section beams subjected to uniformly distributed loads. Additionally, a coupled model termed 'Coupling Reliability Lateral Buckling' (CRLB) is developed to assess the reliability index of steel beams, taking into account the non-linear post-buckling behavior of these beams.

A proposal based on the effective section factor for the lateral-torsional buckling of beams with slender I-shaped welded sections

Lateral-torsional buckling of steel beams with slender cross-sections in case of fire

The effect of residual stresses in the lateral-torsional buckling of steel I-beams at elevated temperature

Lateral-torsional buckling of steel beams with simultaneously tapered flanges and web

Some particular and selected problems aimed at ultimate limit state and probability-based studies pertaining to lateral-torsional buckling of steel beams are described. Stochastic analysis of the ultimate limit state of a slender member IPE220 under bending was elaborated. The values of non-dimensional slenderness for which the statistical characteristics of random load-carrying capacity are maximal were determined. The stochastic computational model was created in the programme ANSYS. Geometric nonlinear solution was employed. In the conclusion of the article, the question of the random effect of the initial rotation of the cross-section on the load-carrying capacity is discussed.

ABSTRACTTapered steel beams are commonly applied in modern steel structures due to their less weight and more optimal solutions of the structural designs. That is why effective engineering solutions of the problem of their lateral‐torsional buckling is expected. In the paper a procedure to solve the problem of calculating critical buckling moment of a tapered beam is proposed with the application of potential energy calculations using Ritz method. Respective solution allows to obtain critical moments initiating lateral buckling of the simply supported, modestly tapered steel I‐beams. In particular, lateral‐torsional buckling of beams with tapered flanges and the web are considered. Detailed, numerical, parametric analyses are carried out. Typical engineering, uniformly distributed design loads are considered for load applied to the top flange, shear centre, as well as to the bottom flange. The parametric analysis of beam with tapered cross‐section, demonstrates that tapering of flanges influences much more the critical moments than tapering of the web.

This study employs experiments and numerical simulation to analyze the dynamic response of steel beams under huge‐mass impact. Results show that lateral torsional buckling (LTB) occurs for a narrow rectangular cross‐section steel beam under transverse impact. The experiments were simulated using LS‐DYNA. The numerical simulation is in good agreement with experimental results, thus indicating that the LTB phenomenon is the real tendency of steel beams under impact. Meanwhile, the study shows that LS‐DYNA can readily predict the LTB of steel beams. A numerical simulation on the dynamic response of H‐shaped cross‐section steel beams under huge‐mass impact is conducted to determine the LTB behavior. The phenomenon of dynamic LTB is illustrated by displacement, strain, and deformation of H‐shaped steel beams. Thereafter, a parametric study is conducted to investigate the effects of initial impact velocity and momentum on LTB. The LTB of H‐shaped cross‐section steel beams under transverse impact is primarily dependent on the level of impact kinetic energy, whereas impact momentum has a minor effect on LTB mode.

Stability of load carrying elements in glass The increasing demand in modern architecture for more slender and lighter structures requires the use of new construction materials. Glass, a material that has been used for a long time in windows as a filling material, has much to offer in this regard due to its very high compressive strength and transparency. For this reason, there is a growing trend to extend the use of glass sheets to load carrying elements such as columns, beams and panels. Due to their high slenderness and high compressive strength, such elements tend to fail because of instability (i.e. column buckling, lateral torsional buckling or plate buckling). At the moment little knowledge exists about the load carrying behaviour of glass structural elements, and existing design methods for other materials (i.e. steel) have been found to be unsuitable for direct transfer to the design of glass panels. With this in mind, the main objectives of the current thesis are: The study of the load carrying behaviour of glass elements which may fail due to lack of stability by means of laboratory tests and analytical and numerical models, as well as the study of the main influencing parameters. Discussion of possible design methods for glass elements which may fail due to lack of stability for the three main stability problems (column buckling, lateral torsional buckling and plate buckling) and proposition of possible aids for design such as buckling curves. The main influencing parameters (dispersion of the glass thickness, initial deformation) on the load carrying behaviour of glass elements which may fail due to lack of stability have been measured and are evaluated herein using statistical methods. The breakage stress, the thermal prestress and the effective tensile strength are defined and explained. Existing models to determine the tensile strength of glass are discussed. The column buckling behaviour of single layer and laminated safety glass is studied by means of column buckling tests, which are compared to analytical and numerical models. The models are used to study the influence of the main parameters, particularly the shear connection due to the interlayer (PVB) in laminated safety glass, on the load carrying behaviour and buckling strength of glass elements. On the basis of this study different possible design methods for column buckling of glass elements in compression are proposed and discussed. It is shown that a second order stress analysis is the most appropriate method for glass. As a further simplification, the cross section of a laminated safety glass structural element can be modelled as a monolithic cross section with an effective thickness. Analytical and numerical models for the lateral torsional buckling of glass beams are also verified by a comparison to test results. Along with a study of the main parameters, different methods to determine the lateral torsional buckling strength are discussed, and it is shown that buckling curves for lateral torsional buckling should be developed for glass beams using a slenderness ratio based on effective tensile strength. As a result of numerical simulations, recommendations for the future development of lateral torsional buckling curves of glass beams are given. The column buckling behaviour of single layer and laminated safety glass is also studied by means of column buckling tests, analytical and numerical models. It is shown that glass panels have a large post critical load carrying capacity but the way the loads are introduced into the panels, as well as the buckling shape, have an important influence on the plate buckling capacity. A design method with buckling curves using a slenderness ratio based on effective tensile strength seems applicable for the design of glass panels. As a result of numerical simulations, recommendations for the future development of plate buckling curves for plate glass elements under compression are given.

This study presents a numerical investigation of the elastic critical lateral-torsional buckling of a steel beam subjected to simultaneous transverse loading at the top flange and negative end moments. Here, the elastic critical buckling of the steel beam was estimated by utilizing the finite element software ABAQUS. In addition, the influence of the length-to-height ratio was taken into account. Additionally, the predicted values for elastic critical buckling when applying existing design codes and a previous study were also analyzed and compared to the numerical results of the finite element analysis. The result of the comparison revealed that the projected values from the design codes and the study are conservative for the majority of cases and have a tendency to be too conservative when the length-to-height ratio increases. Furthermore, a new equation with a factor considering the influence of the length-to-height ratio and transverse loading on the top flange is proposed, and the proposed equation shows sufficient accuracy and less conservative values for most cases.

Numerical and experimental investigation of lateral torsional buckling of wood beams

Elastic buckling of cold-formed steel columns and beams with holes