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Fwd: ASD9 Chapter K

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Charlie,

A careful review of the LRFD shows that Cr carries ksi units and varies
depending on the relationship of Mu to My, which is independent of the steel
type used as My will be determined based on 36 ksi or 50 ksi (in actuality 50
ksi should be used when designing new beams of A36, A992, etc.).  The ASD
equations use only the 6,800 value and don't have a consideration of the flange
thickness/height.  This example is one where the LRFD should be used instead of
the ASD because any current work on stability is expressed in the LRFD.  The ASD
equations are more than 10 years old now and have not been updated for current
research findings, refinements in the equations or consideration of steel
characteristics (dual grade A36, A992, etc.).

Kevin Moore


From: CanitzCF(--nospam--at)aol.com
Subject: Fwd: ASD9 Chapter K
To: seaint(--nospam--at)seaint.org

While checking a beam for sidesway web buckling(Section K1.5), I noticed that
eqns K1-6 and K1-7 do not include Fsuby. If you calculate the equations as
shown, you end up with a in^2 unit, not kips as I would expect. I'm assuming
that the 6800 value must have a ksi unit but wouldn't the limits vary based
upon a 36 ksi vs 50 ksi yield stress or is this already factored in? Chapter
K of the LRFD spec's is similar.

TIA,

Charlie Canitz,PE
Bel Air, MD