To: "'seaint(--nospam--at)seaint.org'" <seaint(--nospam--at)seaint.org>
Subject: RE: AISC Seismic Provisions, Part I, Sect. 11.2a
From: Charlie Carter <carter(--nospam--at)aiscmail.com>
Date: Mon, 7 Jun 1999 09:21:10 -0500
1.1RyMp approximates the plastic flexural strength of the beam after it has
been yielded (represented by Ry) and strain-hardened (represented by 1.1
factor). It is one limit that can be taken to limit the forces for which
the OMF must be designed. Another is if there is a system limitation, such
as foundation uplift, or a column that doesn't (and need not) satisfy the
strong-column weak-beam ratio.
The load combinations in the AISC Specification (Section A4.1) and Seismic
Provisions (Section 4.1) are generally applicable here as well. So in that
sense, you should already have considered the other loads you mentioned
before applying the above limiting conditions. By the way, the special load
combination you mentioned for the shear connection a special one that is
provided in addition to the generally applicable laod combinations.
Hope this helps.
From: Eddie Gonzalez [SMTP:Eagonzal(--nospam--at)ENG.CI.LA.CA.US]
Sent: Friday, June 04, 1999 6:34 PM
Subject: AISC Seismic Provisions, Part I, Sect. 11.2a
Could someone verify if the following interpretation is correct?
11. Ordinary Moment Frames (OMF)
11.2 Beam-to-Column Joints and Connections
11.2a. [Moment Connections]
11.2a.1 states: "FR moment connections that are part of the Seismic Force
Resisting System shall be designed for a required flexural strength Mu that
at least equal to 1.1RyMp [Ry=1.1 for A572,Gr50] of the beam or girder or
maximum moment that can be delivered by the system, which ever is less.
This seems to mean that if 1.1RyMp is the least, then one may ignore Mdl &
If Meq is less, than must include Mdl and/or Mll, depending on the load
combination considered. This may seem obvious except that in item 2, for
Connection, load combination that includes DL & LL & S is specifically
Other documents like FEMA 310 make this issue much more clear.