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Eurocode 3 design rules for the lateral stability of welded I‐members are based on the assumption of hot‐rolled flanges. In practice, a large amount of welded I‐section members is made of flame cut flanges. However, residual stresses of hot‐rolled and flame‐cut flanges are quite different. The latter are more favourable with respect to out‐of‐plane buckling. The beneficial effect of flame‐cuts commonly performed at the flanges tips is then neglected in design standards. A literature review of lateraltorsional buckling tests on welded I‐members with flame‐cut flanges highlights a scarcity of results on mono‐symmetric and/or non‐uniform members. In addition, tests are generally performed on stocky cross‐sections while welded members are usually slender. Lateral‐torsional buckling tests have thus been conducted on four S355 slender welded members made of flame‐cut flanges: two uniform beams and two tapered beams. Within both couples of beams, one had a doubly symmetric cross‐section, the other one being mono‐symmetric. Experimental results highlight the impact of tapering and/or increasing the compression flange thickness whatever the beam type. These experimental tests are then modelled with shell finite elements considering imperfections, residual stresses and material laws measured experimentally. The results are in good agreement with experimental tests. Additional finite element analyses are performed varying the residual stresses distribution. A significant impact of the flange fabrication process is confirmed, flame‐cuts increasing substantially the lateral‐torsional buckling resistance. [ABSTRACT FROM AUTHOR]

As thin walled HSS columns are very flexible, they usually exhibit excessive deformation when resisting a bending moment or transverse loads. Adding exterior/interior diaphragms is one way to remedy the problem. Another option that can significantly increase strength and stiffness is to allow passing plates through the hollow column by means of Laser Cutting Technology (LCT). This solution was tested on CHS columns within the RFCS LASTEICON project. The first outcomes were promising. One of LASTTS new RFCS project's overarching concerns is to enlarge the range of application of the passing‐through solution onto SHS columns. The goal of this research paper is to present the behaviour of I‐beam‐to‐SHS column moment resisting joints using passing‐through plates under opposite bending moments. First, a solid‐based finite element model is presented. This model is used to conduct a sensitivity analysis with different SHS column and passing plates geometry. The failure mode is resulting contribution of both weld/tube‐wall tearing in tension, and chord face crushing in compression. Analytical models are developed in an attempt to ascertain the bending resistance and initial rotational stiffness of this new type of connections. [ABSTRACT FROM AUTHOR]

Conventional I‐beam‐to‐SHS‐column moment resisting connections are generally stiffened with external diaphragms in order to limit excessive deformation of the tube‐wall. Passing through plates welded to the tube is an alternative solution that can develop significant strength and stiffness. This solution has been applied to CHS column and initial findings from RFCS project LASTEICON were encouraging. RHS columns are also widely used in practice due to simplicity of connections manufacturing. The new RFCS project LASTTS aims to investigate the application of this technique of passing through plates to SHS columns using laser cutting technology. The objective of this paper is to present the behaviour of I‐beam‐to‐SHS column moment resisting joints using passing‐through plates under equal hogging bending moments. A finite element model using brick elements is firstly presented. This model is used to perform a sensitivity analysis varying passing through plates thicknesses as well as SHS column dimensions. The failure mode is caused by the flange plate buckling inside the tube. Analytical models are developed to determine the bending resistance and initial rotational stiffness of these connections. [ABSTRACT FROM AUTHOR]

In practice, the elastic lateral‐torsional buckling of doubly symmetric I‐section steel members is analyzed assuming free warping at supports. However, welded stiffeners, bolted end‐plate connections or column base plates maintain elastically the opposite flange out‐of‐plane rotations and thus induce substantial warping restraints. This paper proposes analytical formulations for the evaluation of the elastic critical bending moment for lateral‐torsional buckling of beams taking into account warping restraints at supports. Assuming series of displacement and rotation fields containing one or two terms, the energy method permits to derive expressions of the critical bending moment under constant and linear distribution of the bending moment. A single expression of the warping coefficient kw is proposed whatever the shape of the bending moment diagram. The factor C1 can be conveniently calculated by multiplying two coefficients that depend on the shape of the bending moment diagram and on the warping restraint stiffness, respectively. Finite Elements analyses of beams with warping restraints at supports have been performed considering a beam element model developed with LTBeamN and a shell element model created in ANSYS. The analytical model is in good agreement with the numerical results obtained by the two finite element models. [ABSTRACT FROM AUTHOR]

The current Eurocode 3 rules for buckling of welded I-section members are based on the assumption of hot-rolled flanges. However, flame-cut flanges are widely used in practice and induce significantly different residual stress distributions, affecting the lateral-torsional buckling resistance. Experimental tests and finite element analyses considering residual stress distributions clearly highlighted the beneficial effect of flame-cut flanges compared with hot-rolled flanges on the lateral-torsional buckling resistance of welded I-beams. To complete these preliminary results, a large number of non-linear finite element analyses are performed considering welded beams made of hot-rolled or flame-cut flanges. The beams are composed of steel grades S275 and S355. Numerical results confirm the influence of the flange fabrication process on the buckling behaviour. Eurocode 3 rules are found to be overly conservative for welded beams made of flame-cut flanges. Consequently, proposals are made that are more suitable for estimates of the lateral-torsional buckling resistance of welded beams made of flame-cut flanges. The code rules are also very conservative for welded beams made of hot-rolled flanges with a medium-to-high slenderness. A design method is thus proposed to improve the prediction accuracy of the lateral-torsional buckling resistance of slender welded beams made of hot-rolled flanges. The novel design method from prEurocode 3 provides acceptable values of the buckling resistance for welded beams made of flame-cut flanges but is restricted to uniform doubly symmetric beams. An extension of its scope to mono-symmetric uniform beams as well as tapered beams is thus suggested. An enhanced imperfection factor is proposed, adapted to welded beams made of flame-cut flanges. • Design method to compute the LTB resistance of welded beams with flame-cut flanges using the Eurocode 3 buckling curves. • Design method to compute the LTB resistance of welded beams depending on their geometry, flange fabrication process and bending moment distribution. • Adaptation of the new verification format of prEN 1993–1-1 for lateral-torsional buckling to tapered and/or mono-symmetric beams. [ABSTRACT FROM AUTHOR]

A closed form solution for the ultimate tensile resistance of a bolted flange joint is derived considering yield line failure mechanisms developed by Igarashi et al. The position of the prying force is determined based on formulations previously developed by the authors. Under various simplified assumptions and approximations, a design approach similar to that of the Eurocode 3 for T-stubs is proposed. To validate this approach, experimental tests have been performed on six connections of circular hollow sections made of bolted ring flange. A finite element model considering the elastoplastic behaviour of steel and contact conditions has been developed and the results showed a good agreement with experimental results. Based on the FEM model, a parametric study shows that the proposed analytical model is valid for a wide range of connections. [ABSTRACT FROM AUTHOR]

The buckling behaviour of a steel member is greatly dependent on the residual stress distribution, which is affected by the fabrication process. Indeed, residual stresses in welded steel members are significantly influenced by possible flame-cuts at the flange tips commonly used in practice. However, the Eurocode 3 rules do not account for the beneficial effects of the flame-cuts. Experimental data on commonly used slender members are limited, and therefore to gain further insight an experimental test campaign involving eight slender welded members is carried out. The influence of the flange dimensions and fabrication process was investigated. A new residual stress model is proposed for welded I-sections made of flame-cut flanges integrating results from the literature. Moreover, the actual buckling behaviour of welded members made of flame-cut flanges and/or with a cross section that is not uniform and doubly symmetric is studied. A literature overview of past experimental works highlights the lack of results on common mono-symmetric and/or tapered members, especially for welded members made of flame-cut flanges. An experimental study was thus conducted including lateral–torsional buckling tests on four beams: two uniforms and two tapered. Both types of beams comprised a doubly symmetric and a mono-symmetric I-section. The benefits resulting from tapering and/or increasing the compression flange thickness of an I-section beam are highlighted. The experimental results validate the use of a finite element model for studying the impact of the flange fabrication process on the lateral–torsional buckling resistance. Flame-cuts present at both flange ends increase the ultimate resistance. • Experimental study of residual stresses in welded I-section members made of hot-rolled or flame-cut flanges. • Residual stresses model for welded I-section members with flame-cut flanges. • Lateral–torsional buckling of slender welded I-beams with flame-cut flanges and various geometries. • The resistance to lateral–torsional buckling of a welded beam is greater with flame-cut flanges comparatively to hot-rolled ones. [ABSTRACT FROM AUTHOR]

L-stubs are commonly used to model the tensile parts of ring flange bolted connections. Contact between opposite flanges has a significant effect on the elastic and plastic behaviour of these tensile joints. In the present paper, the effects of contact between flange plates are modelled via a refined beam model which has been previously applied with success to represent the elastic behaviour of non-preloaded L-stubs and T-stubs. Taking into account the behaviour of the flange in the contact area and bolt bending, a model is developed to predict the plastic resistance of L-stub joints. Simplifications are proposed to facilitate the determination of the contact zone and the ultimate resistances corresponding to failure modes involving flange and bolt. The comparison between analytical results with 3D finite element elasto-plastic analyses and experimental tests indicates that the proposed model provides good capacity predictions. Effects of contact, and therefore of the prying force, are particularly important in the case of relatively thin flanges. [ABSTRACT FROM AUTHOR]

Both experimental evidence and 3D finite element analyses indicate that contact forces between the connected parts influence the behaviour of bolted T-stub and L-stub connections in tension. In the present paper, a mechanical model that predict the elastic behaviour of such connections is developed. The model relies on the enhanced beam theory, proposed by Baluch et al. [13], to describe the mechanical response of the flanges in both the contact and the non-contact regions. The model response shows that the contact stresses distribution strongly depends on the ratio between the length of the contact area and the flange thickness. Furthermore, the length of the contact zone in a non-preloaded connection appears to be independent from the magnitude of the external force. Several simplifications have been proposed to facilitate the determination of the separation length which is the primary unknown of the problem. To validate the analytical and calculation models, a 3D finite element model has been developed. Analytical and numerical results are in good agreement which demonstrates the validity of the proposed mechanical model. The theoretical and numerical results confirm that prying action increases with decreasing value of the ratio between the flange stiffness and the bolt stiffness. [ABSTRACT FROM AUTHOR]

Analytical formulations for the evaluation of the critical bending moment for lateral-torsional buckling of a beam taking into account warping restraints at supports are proposed in this paper. A theoretically exact solution is firstly derived from differential equilibrium equations using infinite power series for the twist rotation. Next, the deflected shape is approximated using a single or several base functions for the displacement and rotation fields. The energy method is then used to derive approximate expressions of the critical bending moment of beams subjected to various loading conditions: constant/linear bending moment distributions, mid-span pointwise transverse force or uniformly distributed load. The warping coefficient k w does not depend on the bending moment diagram. The equivalent uniform moment factor C 1 can be conveniently expressed as a product of two coefficients, one related to the bending moment distribution and the other to the warping restraints stiffness. Finite Element analyses of beams with warping restraints at supports have been performed considering a shell elements model created in ANSYS and a beam elements model developed in LTBeamN. • Theoretical exact solution for lateral-torsional buckling with warping restraints • Approximate analytical expressions of M cr in Eurocode 3 format • A single expression of the warping factor k w. • Warping stiffness limit characterizing semi-rigid joints [ABSTRACT FROM AUTHOR]

The present paper deals with an enhanced beam model for semi-infinite prismatic solid in contact with a frictionless rigid support. To circumvent the solution of a plane elasticity problem, we propose an extension of the refined beam theory of Baluch et al. (1985) [6] which accounts for the contact interactions with a frictionless rigid foundation. We combine in a certain way two-dimensional elasticity (plane stress) and the classical engineering beam theory with the aim to derive a refined beam model which takes into account the influence of transverse normal strain as well as contact conditions. The results obtained with the proposed analytical model are compared against semi-analytical solutions for receding contact problems and against refined F.E. analyzes. It is shown that the proposed model provides accurate results and is an efficient tool to tackle problems involving semi-infinite beams in frictionless unilateral contact with a rigid foundation. [ABSTRACT FROM AUTHOR]

Component based finite element design of steel joints This paper describes the principles of multi‐level finite element modelling for design of structural steel joints. The internal part of the design by finite elements is the validation and verification of the model and its results. For models by shell and solid elements is mesh sensitivity study. In component bases finite element design (CBFEB) are the steel plates considered by geometrically and materially non‐linear analysis (GMNA). Its resistance in elastoplastic stage is limited by strains. The behaviour of components, e. g. of bolts, anchor bolts, welds etc., is treated by introducing nonlinear springs representing its behaviour in term of initial stiffness, ultimate resistance and deformation capacity. To show this process a contribution is prepared, which summarises the history of achievements of finite element analyses (FEA) in structural steel connections. This paper shows differences of the research‐oriented and design‐oriented models and the currents trends in modelling of connection components. Both have their roles in advanced analyses. The validation and verification is demonstrated on model of block shear during potential failure mode for gusset plate connection and for the base plates loaded by bending moments to both axes. The summary shows the potential in design of elements including its connection. [ABSTRACT FROM AUTHOR]