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RE: Welded Connection at OMF

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Tom,

 

Thanks.  Yes, I followed all the twists and turns to get to the AISC Seismic Design Manual.  Quite a bit of page turning!  As far as the fillet welds go, you can also use “the maximum moment that can be developed…..”, which in my case is much less than 1.1RyFyAg.  Although the architect doesn’t mind all the full pen welds etc., I also have a steel beam framing through the joint at the same elevation as the connection, I told him he would mind when it is all put together in the field.  Running the beam over the column really simplifies the whole mess.  This morning I was contemplating all the calculations for the beam continuous over the column when I figured that if I (as you have found) that if I use my connection software and turned everything 90 degrees I can save a lot of hand calculations and I’ll have the same “approved” connection (sort of) just column to beam instead of beam to column.  I’m sure I won’t have any trouble with the building official, I have worked with him many times in the past.

 

Thanks again.  Sometimes we just need a bit of confirmation.

Joe

 

From: Tom.Hunt(--nospam--at)fluor.com [mailto:Tom.Hunt(--nospam--at)fluor.com]
Sent: Tuesday, October 28, 2008 10:14 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Welded Connection at OMF

 


Joe,

Backing up a bit just for clarification, you would first have to be sure your system is allowed per ASCE 7-05 Table 12.2-1, including all the footnotes, which by your message it appears you have done.  The next item is the detailing requirements which Table 12.2.1 shoots you to ASCE 7-05 Chapter 14 for a steel OMF, however, IBC Section 1613.1 excludes this chapter but IBC Section 2205.2.2 requires AISC 341 Seismic Detailing in all Design Categories D, E, and F (by now your head should be hurting?!).

Now that you are in AISC 341 Chapter 11 for OMF, Section 11.2a, Item #3 allows your double sided fillet weld but you must design it for 1.1RyFyAg (LRFD) or (1.1/1.5)RyFyAg (ASD).  If you can make your weld work with these numbers then a weld access hole would not be required nor would it be required if you were using a bolted end plate design.  If you were using complete joint penetrating welds on both beam flanges then the access holes would be necessary in order to achieve this type of weld.

Running the beam over the top of the column was not part of the original FEMA 350 testing so you are a little bit on your own for justification but since this is a prescriptive OMF you should be able to get it through the building department if all you numbers work out.  I had this discussion a few years ago with a building official and convinced him it was the same as the tested connection; just turned 90 degrees.

Thomas Hunt, S.E.
Fluor


"Joseph R. Grill" <jrgrill(--nospam--at)cableone.net>
10/27/2008 03:47 PM
Please respond to seaint

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Welded Connection at OMF

 




I have an OMF in a SDC D.  I think I understand from AISC Seismic Provisions that I can use a double sided fillet weld at the beam flange to the column using the maximum moment that can be developed.  Is that correct?  If so, and if I have room to make the double sided fillet by using the width of the flange at the outside and the width minus double the “k” distance at the inside, do I need to provide weld access holes?  11.2a(2) says “where weld access holes are provided…” with the next section saying that double sided fillet welds can be used.  If all this is correct, what is the tolerance for the distance from the beam flange to the column flange to make the fillet weld.  Or am I reading all that incorrectly?
 
The beam at this frame connection is pitched at a 5:12 and in addition I would like to stay away from the full pen weld and all that goes along with it if possible.  This is a custom home project and the weld access holes will create a problem for the architect.
 
I also believe that a connection can be made by running the beam continuous over the column, by using a similar procedure to that used for a wide flange beam over a HSS column as shown in the Hollow Structural Sections Connections Manual.  If not, please let me know.
 
Thanks,
Joe Grill
 
 

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