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

2019 ◽  
Vol 9 (9) ◽  
pp. 1944
Author(s):  
Rafał Piotrowski ◽  
Andrzej Szychowski
Keyword(s):  
Twist Angle ◽  
Major Axis ◽  
Steel Beams ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Critical Moment ◽  
Simple Physical Interpretation ◽  
Approximation Formulas ◽  
Lateral Rotation ◽  
Elastically Restrained

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.

scholarly journals Lateral-Torsional Buckling of Beams Elastically Restrained Against Warping at Supports

2015 ◽  
Vol 61 (4) ◽  
pp. 155-174 ◽  
Author(s):  
R. Piotrowski ◽  
A. Szychowski
Keyword(s):  
Twist Angle ◽  
Symbolic Language ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Beam Loading ◽  
Simple Physical Interpretation ◽  
Theoretical Investigations ◽  
Approximation Formulas ◽  
Accuracy Of Results ◽  
Elastically Restrained

Abstract The study presents the results of theoretical investigations into lateral torsional buckling (LTB) of bi-symmetric I-beams, elastically restrained against warping at supports. Beam loading schemes commonly used in practice are taken into account. The whole range of stiffness of the support joints, from free warping to warping fully restrained, is considered. To determine the critical moment, the energy method is used. The function of the beam twist angle is described with power polynomials that have simple physical interpretation. Computer programs written in symbolic language for numerical analysis are developed. General approximation formulas are devised. Detailed calculations are performed for beams with end-plate joints. Critical moments determined with programs and approximation formulas are compared with the results obtained by other researchers and with those produced by FEM. Very good accuracy of results is obtained.

scholarly journals The Collapse Analysis of the Lateral-Torsional Buckling of I-Shaped Stepped Steel Beams

2020 ◽  
Vol 6 (3) ◽  
pp. 295
Author(s):  
Kelsen Trista Kweenisky ◽  
Naomi Pratiwi ◽  
Paulus Karta Wijaya
Keyword(s):  
Plate Thickness ◽  
Maximum Amplitude ◽  
Cover Plate ◽  
Steel Beams ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Beam Shape ◽  
Critical Moment ◽  
Stepped Beam ◽  
Collapse Analysis

The use of a non-prismatic member such as a stepped beam as a design method has the ability to function as a tool for steel beams optimization. A cover plate is partially welded on the upper and lower flange of the member at the maximum bending moment location to increase its flexural strength and, under critical load, flexural members bend about its strong axis, displace to the lateral direction, and twist coincidentally through a phenomenon known as the Lateral-Torsional Buckling (LTB). There is, however, no equations in the AISC 360-16 specification to calculate the critical moment of a stepped beam (Mst). Therefore, this research focuses on developing Mst for a simply supported stepped beam which deforms on its shear center under static-transverse loading through the use of a collapse analysis and the behavior of the beam. The results showed the welded cover plates consequently increased the LTB resistance of the prismatic I-shaped steel beam from 9.8% to 202% while the critical moment increased more significantly with an increment in the ratio of the cover plate length to the unbraced length (α). The cover plate thickness was observed to have dominantly affected only a large α ratio while the post-buckling characteristic of large α showed a sudden collapse phenomenon. Furthermore, the LTB modification factor was generated in this study due to the initial geometrical imperfection from the first mode of Eigen shape with maximum amplitude Lb/2000 (Cb1) and stepped beam shape (Cst) which were required to estimate the critical moment of a stepped beam based on the AISC equation for a prismatic beam.

scholarly journals Experimental assessment of I-shaped steel beams with longitudinal stiffeners under lateral-torsional buckling

DYNA ◽  
2018 ◽  
Vol 85 (207) ◽  
pp. 278-287
Author(s):  
Néstor I. Prado ◽  
Julian Carrillo ◽  
Gustavo A. Ospina ◽  
Dario Ramirez-Amaya
Keyword(s):  
Lateral Displacement ◽  
Twist Angle ◽  
Steel Beams ◽  
Flexural Capacity ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Experimental Assessment ◽  
Longitudinal Stiffeners ◽  
Simple Support ◽  
Support Conditions

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.

scholarly journals A comparative study of beam design curves against lateral torsional buckling using AISC, EC and SP

2019 ◽  
Vol 15 (1) ◽  
pp. 25-32 ◽  
Author(s):  
Vera V Galishnikova ◽  
Tesfaldet H Gebre
Keyword(s):  
Steel Structures ◽  
Reduction Factor ◽  
Steel Beams ◽  
Steel Beam ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Vertical Loading ◽  
Beam Design ◽  
Overall Stability

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 utilize a reduction factor (χ LT ) to treat lateral torsional buckling problem. In general, flexural capacities according to AISC are higher than those of EC and SP for non-compact sections.

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