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 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 A Study on the Effect of Adjacent Segments of a Steel l-Beam with Lateral Supports on Its Critical Moment

2019 ◽  
Vol 258 ◽  
pp. 05034
Author(s):  
Naomi Pratiwi ◽  
Paulus Karta Wijaya
Keyword(s):  
Failure Modes ◽  
Fem Analysis ◽  
Element Model ◽  
Buckling Analysis ◽  
Steel Beams ◽  
Lateral Torsional Buckling ◽  
Critical Moment ◽  
Collapse Analysis ◽  
Adjacent Segments ◽  
Linear Buckling Analysis

One of the most common failure modes in a steel beam structure is lateral torsional buckling (LTB). The unbraced length of the beam is a crucial factor for LTB analysis. The current formula to calculate the critical moment with respect to LTB analysis has not considered the effect of adjacent segments of steel beams with lateral supports. The adjacent segments of beams actually provide restraints to the torsional rotation while maintaining the possibility of warping to occur. This research was intended to observe the effect of the adjacent segments on its critical moment by using the linear buckling analysis and collapse analysis of a finite-element model. The results from the FEM analysis were compared to the value of the critical moment obtained from the available formula in the standard. The linearised buckling analysis results show an increase in the critical moment by 7.02% to 154.83%, while the collapse analysis results show an increase of 2% to 40.41%. As the adjacent segments becomes longer, the increase is less due to the yielding of adjacent beam segments, contributing less stiflhess to the beam spanning in between lateral supports.

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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