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Fwd: Is SMRSF permitted in Seismic Zone 2?

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I am extremely grateful for the three enlightening responses to my =
posting. I do not wish to repeat my arguments, but I still feel that the =
following points, not touched by any of the three, merit your special =

(a) How does one reconcile the wording of Section 1631.2.7 with that of =
Section 1921.2.1.3, of the UBC? The former says that in Zone 2, the =
frame SHALL AS A MINIMUM, be IMRSF while the latter says that it SHALL =
be IMRSF? Would you not agree that it is ONLY by using an IMRSF, in Zone =
2, that one can reconcile both the said sections?

(b) How would someone using an SMRSF in Zone 2, enter the code for =
meeting the requirements of providing special confinement details, for =
"frames resisting forces induced by earthquakes"? Section 1921.2.1.3 of =
the code unambiguously states that the frames in Zone 2 SHALL be IMRSF =
"proportioned to satisfy ONLY Section 1921.8". On the other hand, the =
detailing requirements -- that would naturally go with an SMRSF -- are =
specified in Sections 1921.2 through 1921.7 of the code, which sections =
are applicable to structures located in Zones 3 and 4 only, under the =
provisions of section 1921.2.1.4.

(c) How would someone using SMRSF in Zone 2, handle the "members not =
part of the lateral load resisting system"? The provisions for such =
members are very lenient for structures falling in Zone 2, as only =
Section 1921.7.2 is applicable to such members, as stipulated in Section =

Very significantly, even ACI 318 does not have ANY special detailing =
requirements for "members not part of the lateral load resisting =
system", for structures falling in Zone 2. Naturally, this facility =
SHOULD not be available if some one uses an SMRSF in Zone 2 and invites =
large inelastic displacements, as a result. To my mind, these large =
displacements are very likely to significantly endanger the structural =
safety of the gravity members. Does this, too, not reinforce the belief =
that significant inelastic action is not INTENDED in Zone 2, in the =
first place -- as would be the case if we were to use an SMRSF -- by any =
of the above two codes?

Perhaps if the word "permitted", used by me in my first posting, is =
replaced with the word "contemplated", my case would become more =

Your help would be greatly appreciated.


Rizwan Mirza, P.E.
Lahore, Pakistan

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Subject: Is SMRSF permitted in Seismic Zone 2?
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Richard Lewis, P.E.
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