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Local buckling design without effective width new developments in the building industry TRB - A2C06 Committee Meeting January 2004 Ben Schafer, Ph.D. The Johns Hopkins University Profiles evolve – how does design keep up? Direct Strength

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

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

direct strength
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.
slide5

Examine bending

Fictitious profile

Local buckling occurs at 0.75 of the reference bending load

slide6

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
conventional approach
Conventional approach
  • Via a specification we get
  • all local buckling modes,
  • effective widths,
  • effective properties, and
  • finally the strength.
direct strength approach
Direct Strength Approach
  • Via alternative we get
  • all local buckling modes calculated exactly, and
  • the strength.
direct strength for pipe

M,T

Direct Strength for Pipe…

(could be strain based)

thrust columns
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

bending beams
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, b=2.5, f=0.9

dsm for flexible pipe
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 simplificationandoptimization.