Local buckling design without effective width new developments in the building industry

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Local buckling design without effective widthnew
developments in the building industry

• TRB - A2C06 Committee Meeting
• January 2004
• Ben Schafer, Ph.D.
• The Johns Hopkins University

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Profiles evolve how does design keep up?
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Direct Strength

• In the building industry we have recently added a
  new alternative method for local buckling design
  that
• requires no effective width calculation, and
• incorporates a numerical analysis that accurately
  predicts local buckling even for complicated
  cross-sections.

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Fictitious profile
Examine bending
Local buckling occurs at 0.75 of the reference
bending load
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Idea for incremental profile improvement
Local buckling at 4 times reference Local
buckling at 2.7 times reference

• Big boost from 0.75! I want to take advantage of
  that.
• hard to calculate by hand
• effective width becomes overly complicated

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Conventional approach

• Via a specification we get
• all local buckling modes,
• effective widths,
• effective properties, and
• finally the strength.

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Direct Strength Approach

• Via alternative we get
• all local buckling modes calculated exactly, and
• the strength.

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Direct Strength for Pipe
(could be strain based)
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Thrust - Columns

• Lipped channels
• Lipped zeds
• Lipped channels with int. web stiffener
• Hat sections
• Rack post sections

267 columns , b 2.5, f 0.84
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Bending - Beams

• Lipped and plain channels
• Lipped zeds
• Hats with and without intermediatestiffener(s)
  in the flange
• Decks with and without intermediate stiffener(s)
  in the web and the flange

569 beams, b2.5, f0.9
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DSM for flexible pipe?

• More research would be needed to bring the Direct
  Strength Method to flexible pipe, but the
  existing research plus the success of the AASHTO
  method demonstrate it is possible.
• Design for thin-walled flexible pipe has
  benefited from existing research, new design
  methods provide new opportunities for
  simplification and optimization.

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www.ce.jhu.edu/bschafer
CUFSM
DSM
Pipe