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

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

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  1. 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

  2. Profiles evolve – how does design keep up?

  3. 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.

  4. Examine bending Fictitious profile Local buckling occurs at 0.75 of the reference bending load

  5. 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

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

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

  8. M,T Direct Strength for Pipe… (could be strain based)

  9. 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

  10. 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

  11. 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.

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

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