Impact of Support Closed Section Ribs on the Critical Moment for Lateral Torsional Buckling of Steel Beams

Piotrowski, Rafał; Szychowski, Andrzej

doi:10.30540/sae-2018-001

Cited by 4 publications

(6 citation statements)

References 4 publications

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“…It was shown that the use of support ribs with closed section significantly increased the critical loading of the beams of under consideration. In study [37], the influence of various types of supporting ribs with a closed cross-section on the critical moment of the lateral torsional buckling for differently loaded beams was examined. Detailed calculations were made for uniformly loaded beams.…”

Section: Introductionmentioning

confidence: 99%

Lateral Torsional Buckling of Steel Beams Elastically Restrained at the Support Nodes

Piotrowski

Szychowski

2019

Applied Sciences

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The study shows the results of theoretical investigations into lateral torsional buckling of bisymmetric I-beams elastically restrained against warping and against rotation in the plane of lateral torsional buckling (i.e., against lateral rotation) at the support nodes. The analysis accounted for the whole variation range of node stiffnesses, from complete warping freedom to full restraint, and from complete lateral rotation freedom to full restraint. It was assumed the beams are simply supported against bending about the major axis of the section. To determine the critical moment, the energy method was used. Both the twist angle function and the lateral deflection function of the beam were described using power polynomials with simple physical interpretation. Computer programmes were developed to make numerical and symbolic “computations”. General approximation formulas for the critical moment for lateral torsional buckling were derived. The formulas covered the basic and most frequently found loading diagrams. Detailed computations were performed for different values of the index of fixity against warping and against rotation in the plane of lateral torsional buckling. The critical moments determined using the programmes devised and approximation formulas were compared with the values obtained with LTBeam software (FEM). A very good congruence of results was found.

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Section: Introductionmentioning

confidence: 99%

Lateral Torsional Buckling of Steel Beams Elastically Restrained at the Support Nodes

Piotrowski

Szychowski

2019

Applied Sciences

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“…The analysis of the warping stiffness of different types of stiffeners [ 31 , 32 ] showed that the effect produced by curbing the beam section’s warping was negligibly small when flat stiffeners (of commonly found thicknesses) were used, compared with closed-section stiffeners. Consequently, the contribution of flat stiffeners t p = 8 mm, located in the axis of the B–E critical beam ( Figure 1 b), was neglected when the stiffness of the beam elastic restraint against warping α ω (6) was determined, i.e., it was assumed that α ω R = 0.…”

Section: The Model Of Designated Critical Beam (Methods 3)mentioning

confidence: 99%

“…For each of the span variants, two types of stiffening were taken into consideration at joints B and E, namely flat stiffeners ( Figure 1 b) and closed-section stiffeners ( Figure 1 c). These two methods of stiffening are characterised by a large disparity in the obtained warping stiffness [ 31 , 32 ]. It was assumed that the homogeneous grillage beams were weld-connected at joints B and E. In this way, it was possible to obtain full continuity in the transmission of displacements, including warping, and in the transmission of cross-sectional forces, including bimoments.…”

Section: Diagram Of the Analysed Structurementioning

confidence: 99%

Elastic Critical Resistance of the Simple Beam Grillage Resulting from the Lateral Torsional Buckling Condition: FEM Modelling and Analytical Considerations

2023

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Transversely loaded beam grillages are quite often used in industrial construction. In order to produce a safe design of such structures, it is necessary to account for the lateral torsional buckling phenomenon, which reduces load-bearing capacity. To be able to calculate the relevant reduction factor, the elastic critical load must be determined. As regards the existing design practice for such structures, simplified conditions are assumed for the mutual restraint of the component beams. However, this approach does not correspond to reality. This study discusses the results of numerical investigations and analytical calculations concerning the effect of the elastic action of simple beam grillage (SBG) joints on the critical load, which results from the lateral torsional buckling (LTB) condition. The SBG was defined as a flat system of interconnected beams, unstiffened laterally and loaded perpendicularly to the grillage plane. The analysis covered H-shaped grillages with different span ratios of component beams, in which the main (coupling) beam was decisive for instability. The effectiveness of the use of closed-section stiffeners at the grillage joints was also investigated. The grillage elastic critical resistances (ECR) were determined for two variants of joint stiffening. The computations were performed by means of FEM numerical simulations. The spatial models were discretised with the following elements: (1) solid ones in Abaqus, (2) shell ones in ConSteel, and (3) thin-walled bars in ConSteel. The LTB critical moments of the weakest beam (critical beam), elastically restrained against warping and against lateral rotation (in the LTB plane), were computed using the analytical methods developed by the authors. To this end, the methods were proposed to determine the indexes of the critical beam elastic restraint in the adjacent stiffening beams. In the study, it was demonstrated that (1) taking into account the conditions of mutual elastic restraint and interaction of the component beams provides a more accurate assessment of the grillage ECR, (2) the use of closed-section stiffeners in the grillage joints increase the ECR compared with classic flat stiffeners, (3) the grillage ECR can be estimated based on the critical moment Mcr of the weakest beam (critical beam) when the conditions of its elastic restraint in joints are accounted for.

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“…In order to enhance beam resistance to LTB, systems of support ribs for beams (spandrel beams) were developed. They were meant to increase the deplanation rigidity of support cross sections [33][34][35][36][37][38]. Methods for analysing beams discretely braced along their span were discussed in [39][40][41][42].…”

Section: Introductionmentioning

confidence: 99%

“…It was indicated that ribs (especially closed ones) and discrete elastic bracings considerably affect the values of critical loads. The authors of [20,23,33,34,36,37,[43][44][45][46], analysed the impact of elastic restraint against warping of support cross sections for single-span beams with bisymmetric cross sections. The impact of elastic restraint against warping of the cantilever beam free end on its critical resistance caused by the LTB condition was examined in [47].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Steel Beam Elastic Restraint on the Critical Moment of Lateral Torsional Buckling

Piotrowski

Szychowski

2022

Materials

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This paper reports the results of the next stage of the authors’ investigations into the effect of the elastic action of support nodes on the lateral torsional buckling of steel beams with a bisymmetric I-section. The analysis took into account beam elastic restraint against warping and against rotation in the bending plane. Such beams are found in building frames or frame structures. Taking into account the support conditions mentioned above allows for more effective design of such elements, compared with the boundary conditions of fork support, commonly adopted by designers. The entire range of variation in node rigidity was considered in the study, namely from complete freedom of warping to complete restraint, and from complete freedom of rotation relative to the stronger axis of the cross section (free support) to complete blockage (full fixity). The beams were conservatively assumed to be freely supported against lateral rotation, i.e., rotation in the lateral torsional buckling plane. Calculations were performed for various values of the indexes of fixity against warping and against rotation in the beam bending plane. In the study, formulas for the critical moment of bilaterally fixed beams were developed. Also, approximate formulas were devised for elastic restraint in the support nodes. The formulas concerned the most frequent loading variants applied to single-span beams. The critical moments determined in the study were compared, with values obtained using LTBeamN software (FEM). Good compliance of results was observed. The derived formulas are useful for the engineering design of this type of structures. The designs are based on a more accurate calculation model, which, at the same time offers simplicity of calculation.

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Impact of Support Closed Section Ribs on the Critical Moment for Lateral Torsional Buckling of Steel Beams

Cited by 4 publications

References 4 publications

Lateral Torsional Buckling of Steel Beams Elastically Restrained at the Support Nodes

Lateral Torsional Buckling of Steel Beams Elastically Restrained at the Support Nodes

Elastic Critical Resistance of the Simple Beam Grillage Resulting from the Lateral Torsional Buckling Condition: FEM Modelling and Analytical Considerations

The Effect of Steel Beam Elastic Restraint on the Critical Moment of Lateral Torsional Buckling

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