• Title, Summary, Keyword: torsional buckling

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Analytical and Parametric Investigations on Lateral Torsional Buckling of European IPE and IPN Beams

  • Yilmaz, Tolga;Kirac, Nevzat
    • International journal of steel structures
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    • v.17 no.2
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    • pp.695-709
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    • 2017
  • Lateral torsional buckling is one of the main failure modes controlling the strength of the slender thin-walled members. A transversely or transversely and axially combined loaded member that is bent with respect to its axis of greatest flexural rigidity may buckle laterally and twist as applied load reaches its critical value unless the beam is provided with a sufficient lateral support. This study intends to present a unique convenient equation that it can be used for calculating critical lateral-torsional buckling load of simply supported European IPE and IPN beams. First, an analytical model is introduced to describe lateral-torsional buckling behavior of beams with monosymmetric cross-section. The analytical model includes first order bending distribution, load height level and monosymmetry property of the section. Then, parametric study is carried out using the analytical solutions in order to establish a simplified equation with dimensionless coefficients. The effect of slenderness and loading positions on lateral-torsional buckling behavior of IPE and IPN beams are studied. The proposed solutions are compared to finite element simulations where thin-walled shell elements and beam elements including warping are used. Good agreement between the analytical, parametric and numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of European IPE and IPE beams can be determined by presented equation and can be safely used in design procedures.

Torsional Buckling Behavior of Composite Cylinder (복합재 실린더의 비틀림 좌굴 특성 연구)

  • 이춘우;권진회
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.92-95
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    • 2002
  • A nonlinear finite element method is presented to evaluate the torsional buckling moment and failure of composite laminated cylinders. For the progressive failure analysis, the complete unloading method is used based on the maximum stress failure criteria. An arc-length method is incorporated to trace the postbuckling equilibrium path. Present finite element method is verified by the existing experimental and analytical results. The results of the parametric study show that the torsional buckling moments are sensitive to the geometric change, but are not much affected by the lay-up angle. All cylinders tested numerically show the unstable torsional buckling, and therefore the torsional buckling always leads to the catastrophic failure.

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Inelastic lateral-torsional buckling strengths of stepped I-beams subjected to general loading condition

  • Park, Jong Sup;Park, Yi Seul
    • Structural Engineering and Mechanics
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    • v.48 no.2
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    • pp.275-289
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    • 2013
  • The cross sections of multi-span beams are sometimes suddenly increased at the interior support of continuous beams to resist high negative moment. An earlier study on elastic lateral torsional buckling of stepped beams was conducted to propose new design equations. This research aims to continue the earlier study by considering the effect of inelastic buckling of stepped beams subjected to pure bending and general loading condition. A three-dimensional finite element-program ABAQUS and a statistical program MINITAB were used in the development of new design equations. The inelastic lateral torsional buckling strengths of 36 and 27 models for singly and doubly stepped beams, respectively, were investigated. The general loading condition consists of 15 loading cases based on the number of inflection point within the unbraced length of the stepped beams. The combined effects of residual stresses and geometrical imperfection were also considered to evaluate the inelastic buckling strengths. The proposed equations in this study will definitely improve current design methods for the inelastic lateral-torsional buckling of stepped beams and will increase efficiency in building and bridge design.

An alternative evaluation of the LTB behavior of mono-symmetric beam-columns

  • Yilmaz, Tolga;Kirac, Nevzat;Anil, O zgur
    • Steel and Composite Structures
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    • v.30 no.5
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    • pp.471-481
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    • 2019
  • Beam-columns are structural members subjected to a combination of axial and bending forces. Lateral-torsional buckling is one of the main failure modes. Beam-columns that are bent about its strong axis may buckle out of the plane by deflecting laterally and twisting as the values of the applied loads reach a limiting state. Lateral-torsional buckling failure occurs suddenly in beam-column elements with a much greater in-plane bending stiffness than torsional or lateral bending stiffness. This study intends to establish a unique convenient closed-form equation that it can be used for calculating critical elastic lateral-torsional buckling load of beam-column in the presence of a known axial load. The presented equation includes first order bending distribution, the position of the loads acting transversely on the beam-column and mono-symmetry property of the section. Effects of axial loads, slenderness and load positions on lateral torsional buckling behavior of beam-columns are investigated. The proposed solutions are compared to finite element simulations where thin-walled shell elements including warping are used. Good agreement between the analytical and the numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of beam-columns with mono-symmetric sections can be determined by the presented equation and can be safely used in design procedures.

I-girder with Discrete Torsional Bracing: Lateral-torsional Buckling and Torsional Free Vibration (I-거더 불연속 비틀림 브레이싱: 횡-비틂 좌굴 및 비틀림 자유진동)

  • Nguyen, Cahn Tuan;Moon, Ji-Ho;Kim, Hyun-Soo;Lee, Hak-Eun
    • 한국방재학회:학술대회논문집
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    • pp.85-85
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    • 2010
  • Discrete torsional bracing systems are widely used in practice to increase the strength of I-girders bridges. This paper proposes equations for lateral-torsional buckling strength, torsional natural frequency and stiffness requirements of I-girders with discrete torsional bracings. Firstly, the equations to calculate the critical moment of the I-girder with discrete torsional bracings are introduced. The proposed equations are then compared with the results of finite element analyses and those from previous studies. The equations to calculate the torsional natural frequency are also presented in the same manner. From the results, it is found that proposed equations agree well with results of finite element analyses regardless of the number of bracing points. Finally, the reduced formula for the total torsional stiffness requirement is proposed for the design purpose.

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Evaluation of Lateral-Torsional Buckling Strength of I-Girder with Corrugated Web under Uniform Bending (균일한 휨모멘트가 작용하는 파형강판 복부판 I-거더의 횡-비틂 좌굴강도 평가)

  • Moon, Ji Ho;Yi, Jong Won;Choi, Byung Ho;Lee, Hak Eun
    • Journal of Korean Society of Steel Construction
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    • v.19 no.5
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    • pp.463-472
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    • 2007
  • This paper presents theoretical and finite element analysis results for the lateral-torsional buckling of I-girders with corrugated web under uniform bending. Lateral-torsional buckling is a major design aspect for flexural members composed of thin-walled I-section. However, torsional rigidities such as the warping constants of the I-girders with corrugated web are not fully understood yet. In this paper, bending and pure torsional rigidities of I-girders with corrugated web are first described using the results of previous researchers. Then, the location of the shear center and the warping constants are derived. Using the derived section properties of I-girders with corrugated web, the lateral-torsional buckling strength is determined. Finite element analyses are conducted and the proposed lateral-torsional buckling strength of I-girders with corrugated web is successfully verified. Finally, the effects of corrugation profiles of the web on the lateral-torsional buckling load of I-girders with corrugated web are discussed.

Elastic Buckling Behavior of Orthotropic Equal-leg Angle Members (직교이방성 등변앵글부재의 탄성좌굴)

  • 김정곤;윤순종
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.54-59
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    • 2001
  • This paper presents an analytical investigation pertaining to the elastic buckling behavior of pultruded fiber reinforced plastic equal-leg angle members under concentric axial compression. The elastic local and global buckling (flexural, torsional, and flexural-torsional) analyses are conducted, respectively, and the analytical results are compared with the existing experimental results. The differences were more than 10%, and the experimental results were higher than the analytical results.

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Flexural-torsional buckling tests of cold-formed steel compression members at elevated temperatures

  • Heva, Yasintha Bandula;Mahendran, Mahen
    • Steel and Composite Structures
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    • v.14 no.3
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    • pp.205-227
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    • 2013
  • Current design standards do not provide adequate guidelines for the fire design of cold-formed steel compression members subject to flexural-torsional buckling. Eurocode 3 Part 1.2 (2005) recommends the same fire design guidelines for both hot-rolled and cold-formed steel compression members subject to flexural-torsional buckling although considerable behavioural differences exist between cold-formed and hot-rolled steel members. Past research has recommended the use of ambient temperature cold-formed steel design rules for the fire design of cold-formed steel compression members provided appropriately reduced mechanical properties are used at elevated temperatures. To assess the accuracy of flexural-torsional buckling design rules in both ambient temperature cold-formed steel design and fire design standards, an experimental study of slender cold-formed steel compression members was undertaken at both ambient and elevated temperatures. This paper presents the details of this experimental study, its results, and their comparison with the predictions from the current design rules. It was found that the current ambient temperature design rules are conservative while the fire design rules are overly conservative. Suitable recommendations have been made in relation to the currently available design rules for flexural-torsional buckling including methods of improvement. Most importantly, this paper has addressed the lack of experimental results for slender cold-formed steel columns at elevated temperatures.

Distortional buckling of I-steel concrete composite beams in negative moment area

  • Zhou, Wangbao;Li, Shujin;Huang, Zhi;Jiang, Lizhong
    • Steel and Composite Structures
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    • v.20 no.1
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    • pp.57-70
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    • 2016
  • The predominant type of buckling that I-steel concrete composite beams experience in the negative moment area is distortional buckling. The key factors that affect distortional buckling are the torsional and lateral restraints by the bottom flange. This study thoroughly investigates the equivalent lateral and torsional restraint stiffnesses of the bottom flange of an I-steel concrete composite beam under negative moments. The results show a coupling effect between the applied forces and the lateral and torsional restraint stiffnesses of the bottom flange. A formula is proposed to calculate the critical buckling stress of the I-steel concrete composite beams under negative moments by considering the lateral and torsional restraint stiffnesses of the bottom flange. The proposed method is shown to better predict the critical bending moment of the I-steel composite beams. This article introduces an improved method to calculate the elastic foundation beams, which takes into account the lateral and torsional restraint stiffnesses of the bottom flange and considers the coupling effect between them. The results show a close match in results from the calculation method proposed in this paper and the ANSYS finite element method, which validates the proposed calculation method. The proposed calculation method provides a theoretical basis for further research on distortional buckling and the ultimate resistance of I-steel concrete composite beams under a variable axial force.

Lateral buckling formula of stepped beams with length-to-height ratio factor

  • Park, Jong Sup
    • Structural Engineering and Mechanics
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    • v.18 no.6
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    • pp.745-757
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    • 2004
  • Lateral-torsional buckling moment resistances of I-shaped stepped beams with continuous lateral top-flange bracing under a single point load on the top flange and negative end moments were investigated. Stepped beam factors and a moment gradient correction factor suggested by Park et al. (2003, 2004) were used to develop new lateral buckling formula for beam designs. From the investigation of finite element analysis (FEA), new lateral buckling formula of beams with singly or doubly stepped member changes and with continuous lateral top-flange bracing subjected to a single point load on top flange and end moments were developed. The new design equation includes the length-to-height ratio factor to account for the increase of lateral-torsional buckling moment resistance as the increase of length-to-height ratio of stepped beams. The calculation examples for obtaining lateral-torsional buckling moment resistance using the new design equation indicate that engineers should easily determine the buckling capacity of the stepped beams.