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RE: SDC D Ordinary Moment frame connection using HSS sections

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Regarding OCBF, there are virtually no serious requirements other than the connection strength ( >= 2*design force).
If HSS braces are used, I would keep the gusset plates since they allow out of plane buckling of braces which enhances energy dissipation.
Suresh Acharya, S.E.

From: Joseph R. Grill [mailto:jrgrill(--nospam--at)]
Sent: Thursday, August 14, 2008 12:54 PM
To: seaint(--nospam--at)
Subject: RE: SDC D Ordinary Moment frame connection using HSS sections

Mark and Suresh,

I did see the note in Section 11.1.  It's been a long time since I've done one of these (pre IBC).  In going through the seismic manual I saw the note, but couldn't envision how to make the connection.  Mark, your idea sounds great.  However in reviewing other criteria for the OMF I don't think I can comply with some of those, such as bracing as this is a frame within a stair tower with no floors or perpendicular framing at the horizontal beam locations.


The fabricator is open to a concentric braced frame.  I'm looking at single diagonals in the bays (3 bays high x 1bay long).  I think this works.  I do, however have a question regarding this.  I would think that the diagonals could be welded directly at the column beam intersections without gusset plates.  I don't see a requirement for the use of gussets.  Am I correct there.  The loads shouldn't be very high.


Thanks for the idea.



From: Mark D. Baker [mailto:shake4bake(--nospam--at)]
Sent: Thursday, August 14, 2008 9:01 AM
To: seaint(--nospam--at)
Subject: RE: SDC D Ordinary Moment frame connection using HSS sections




Section 11.1 of the Seismic Provisions for Structural Steel Buildings, AISC 341-05 says:


"While these provisions for OMF were primarily developed for use with wide flange shapes, with judgment, they may also be applied to other shapes such as channels, built-up sections, and hollow structural sections (HSS)"


In the situation where column meets beam and the column does not continue past beam, cut ends of column and beam at 45, backing can be installed for this joint.


Where column does run past beam, cut notch in column in a V shape (female end) and cut end of beam in a V shape (male end) to insert into the column notch. This joint also will be able to receive backing plates.


You are correct that when trying to join the beam to the column face, full pen welds are nearly impossible.




Mark D. Baker

Baker Engineering


From: Joseph R. Grill [mailto:jrgrill(--nospam--at)]
Sent: Wednesday, August 13, 2008 9:28 PM
To: seaint(--nospam--at)
Subject: SDC D Ordinary Moment frame connection using HSS sections


Can HSS sections be used in an Ordinary Moment Frame in a SDC D.  I can't see, in the seismic design manual,  where it is specifically excluded, but I can't find any information for the HSS Beam to HSS column connection design.  It seems that it can't be done since a full pen weld is difficult if not impossible to do for a HSS beam to HSS Column face.  If there is an example out there I would love to see it.  I am doing some work for a fabricator and they are expecting HSS sections due to what is seen in the construction documents.  I have to let him know real soon if he will need to go to wide flange members.


Thanks for the help,

Joe Grill


Joseph R. Grill, PE

Verde Valley Engineering, PLLC

2220 Sky Drive

Clarkdale, AZ 86324

Ph. (928) 600-5459

Fax (928) 649-3659

email: VVEng(--nospam--at)