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Watch for the additional drift.  I have seen people make the same decision and then regret it when it comes time to detail brick veneers and the like.  The EBF's are clearly a better system for seismic loads, but there are some penalties.  Isolating architectural elements can be a real pain when drifts become problematic.
Jake Watson, P.E.
Salt Lake City, UT
-----Original Message-----
From: Dan Hernandez [mailto:dhernandez(--nospam--at)]
Sent: Wednesday, May 21, 2003 1:00 PM
To: seaint(--nospam--at)
Subject: RE: OCBF

I see that you're correct about section 14.3a. The beam to column connection should account for the RyFyAg force of the brace. I suppose
the horizontal component of the brace force should equal the beam axial force.
As to the brace design forces, I too have found that the forces are much higher than the force due to load combinations. So much so that
I'm going to switch from OCBF's to EBF's. The R value is much higher so the seismic forces will be reduced and the connection requirements
for my braces are less stringent in terms of load. A little more detailing (link detailing requirements) but I think worth it. 
-----Original Message-----
From: Seth W. Cutler [mailto:seth(--nospam--at)]
Sent: Wednesday, May 21, 2003 2:00 PM
To: seaint(--nospam--at)
Subject: Re: OCBF


I've been working on interpreting this for a couple weeks now and I'm still not really sure what the current methodology is.  My current feel for this is that the beam-column connection should be designed based on the same load as the brace connections.
  This is because AISC Seismic Provisions (1997) Part 1, Section 14.3a includes it in it's design requirements.  I think it just makes sense if you have to design those other connections like that, it should be carried all the way thru.

Now, my issue with this is we have to design for the expected tensile strength of the brace.  Now, this becomes a fairly high load for some of my connections when the expected load is no where close.  Compression controls all of the braces because of their KL/r ratio.  Are you seeing this as well?


At 05:07 AM 5/21/2003, you wrote:
I need help. I'm a little confused about how to design brace connections. According to AISC Seismic Provisions (1997) Supplement No.2 Part 1, Section 14.2 it states that " The required strength of the members and connections, other than brace connections, in OCBFs shall be based upon Load Combinations 4-1 and 4-2. ..."  The 2002 commentary to AISC Seismic Provisions define brace connections as brace to gusset, gusset to beam and gusset to column. How am I to design the beam to column connection? If I'm to use the uniform force method then the force in the brace affects the beam to column connection design force. Am I missing something? I thought the brace connection included the beam to column connection.
Thanks in advance,
Dan Hernandez, P.E.
Laurene & Rickher, P.C.
(704) 522-0495
(704) 522-0499 f