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B31.1 S_A w/ "Footnote 2" Materials

B31.1 S_A w/ "Footnote 2" Materials

B31.1 S_A w/ "Footnote 2" Materials

(OP)
This probably falls into "who cares?" but I'm still curious.

Reference B31.1 equations 1A (S_A), 1B (S_A liberal), 11a (S_L), and footnote 2:

"For materials with a minimum tensile strength over 70ksi, eqs (1A) and (1B) shall be calculated using S_c or S_h values no greater than 20ksi, unless otherwise justified."

With a material that qualifies for that footnote, S_c = 25ksi, S_h = 25ksi.  I could push S_L to 25ksi.  Equation (1A) (f=1.0) would give 30ksi considering the 20ksi max for S_c and S_h, but the liberal allowable would be:
1.0*(1.25*S_c + 0.25*S_h + (1.0*S_h - 1.0*S_L)) = 25ksi.

Eq 1A = 30ksi
Eq 1B = 25ksi

This seems counter-intuitive to me.  Is that how you read the code as well?

Should the sustained load margin be taken with S_h = 25ksi still?  Would that fall under "further justification"?  1B simplifies things down to one S_h term, so maybe that is not stretching.

- Steve Perry
http://www.linkedin.com/in/stevenhperry
This post is designed to provide accurate and authoritative information in regard to the subject matter covered.  It is offered with the understanding that the author is not engaged in rendering engineering or other professional service.  If you need help, get help, and PAY FOR IT.

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