Lateral–Torsional Buckling Response of As-built and Heat-straightened Welded Steel Girders

• Author / Creator

  Twizell, Sheldon C.

• Lateral–torsional buckling (LTB) is a stability failure mode that occurs in unbraced segments of flexural members and is associated with simultaneous out-of-plane lateral defection and cross-section rotation. The LTB behaviour of doubly symmetric I-shaped members is generally well understood. However, there is concern that current understandings of inelastic LTB in welded steel girders may be inaccurate and not representative of the current fabrication methods employed in Canada. Moreover, recent studies (MacPhedran and Grondin 2011; Kabir and Bhowmick 2018) have indicated the current Canadian design provisions for LTB may be inaccurately estimating the inelastic LTB resistance of welded steel girders. The purpose of this study is to address these concerns and assess the LTB behaviour of modern welded steel girders through experimental and numerical means. Additionally, to assess the LTB behaviour and load-carrying performance of heat-straightened welded steel girders.

  The experimental portion of this study includes the large-scale testing of four welded steel girders and five heat-straightened girders of intermediate slenderness. The test results were used to examine the LTB behaviour of welded steel girders and assess the stability response of heat-straightened girders through comparison with the as-built response. A continuum finite element model was developed and calibrated against the experimental test results and was used to simulate the experimental specimens for two loading conditions: top flange and shear centre. The adequacy of the CSA S16-19 design provisions for welded steel girders was then evaluated by comparing the code-predicted moment resistances with those of finite element analysis. The CSA S16-19 design equation is found to adequately estimate the moment resistance of modern welded steel girders; however, CSA S16-19 can overestimate the moment resistance of girders with large web width-to-thickness ratios and high initial geometric imperfection.

• Subjects / Keywords

  • lateral–torsional buckling
  • heat-straightening
  • experimental test
  • finite element analysis
  • finite element model
  • CSA S16-19
  • CSA W59-18
  • welded steel girder
  • geometric imperfection
  • residual stress
  • lateral–distortional buckling
  • load height
  • beam
  • girder
  • steel
  • flexure

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-ccjy-hh09

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.