AISC


Ad Hoc Task Group Report on Local Buckling (Width-to-thickness) Limits

  • Primary Investigator(s): Ben Schafer
  • Institution: AISC Committee on Specifications Task Group on Local Buckling (Width-to-thickness) Limits
  • Year Completed: 2020

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Description

The AISC Committee on Specification established an ad hoc task group to provide input on the following issues related to local buckling requirements (i.e., width-to-thickness ratios):

  1. Recommend objective of each width-to-thickness (lamda) limit in ANSI/AISC 360, Specification for Structural Steel Buildings (AISC 360) and ANSI/AISC 341 
    Seismic Provisions for Structural Steel Buildings (AISC 341)
    1. Explicitly state the objective (Mp, R, θp etc.) for all λr, λp, λmd, λhd, etc.
      Note, the objective may be system dependent, particularly in AISC 341
    2. Insure these objectives are clear to the user (through commentary, guides, user notes etc.)

  2. Review all width-to-thickness (lambda) limits in AISC 360 and 341 against objective criteria
    1. Recommend updated λ limits when not aligned with objectives
    2. Document source of all existing lamda limits
  3. Provide recommendation on material criteria and application in lambda limits
    1. Recommend whether nominal or expected Fy is appropriate for λ limits in 341 and 360
    2. Provide guidance on other material criteria implicit in λ limits (Fu/Fy, Est, COV of Fy, etc.)
  4. Recommend a consistent approach for web/flange interaction in AISC 360 and 341 λ limits
    1. Provide guidance on when web/flange interaction should be considered to meet objectives
    2. Review AISC 360 λ limits regarding web/flange interaction and provide recommendations
    3. Review AISC 341 λ limits regarding web/flange interaction and provide recommendations - Note, recent deep column research indicates changes will be needed at least in AISC 341  
  5. Provide recommendation on alternatives to use of lambda limits to achieve objectives
    1. Identify alternative means for establishing performance onjectives established in 1
      1. Continuous Strength Method of Gardner et al.?
      2. AISC 341 Appendix 1 supported analysis provisions?
      3. Testing pathways?
    2. Insure Specifications provide users pathways to alternative means when λ is an impediment

Additional Committee Member Participants

Ben Schafer, Chairman (TC 4)
Tim Fraser (TC 6)
Subhash Goel (TC 9)
Pat McManus (TC 9)
Don Sherman (TC 4)
Tom Sabol (TC 9)
Chia-Ming Uang (TC 4)
Amit Varma (Fire, TC 5)
Brent Leu, Secretary