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RE: UBC 1630, Ev Question

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Tom Hunt wrote:

"UBC Section 1630.1.1 Equation 30-1 requires E = pEh + Ev which is stated to be
used in the load combinations of Section 1612.  In Section 1612.2.1, Basic Load
Combinations, "E" appears in two equations, 12-5 and 12-6.  HOWEVER, in reading
the SEAOC Blue Book, Ev was intended for equation 12-5 ONLY (See Blue Book
commentary C105.1.1 and Equation 101-5).

Was this a mistake or did ICBO/UBC conscientiously change this??  For a regular
building, this has the effect of changing equation 12-6 to 0.7D +/- 1.0E.  This
probably wont effect footing sizing since they are sized using allowable load
design but this could throw concrete columns into tension and could increase
anchor bolt diameter and embedment if you are using strength design (ACI 349
approach)."

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Mark Deardorff responded:

According to the ICBO seminar I attended last fall it will be corrected in the
2000 IBC. I don't recall seeing it in the draft, however.

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The 1997 UBC specifically excludes E-sub-v from allowable stress combinations.

The 2000 IBC doesn't have an E-sub-v term.  It uses 0.2S-sub-DS D instead.
However, the IBC doesn't exclude 0.2S-sub-DS D from allowable stress
combinations.  That means that the IBC will essentially require 0.7D +/- 1.0E
for foundation design.  This will probably result in LARGE foundations.

Rick Drake, SE
Fluor Daniel, Aliso Viejo