Return to index: [Subject] [Thread] [Date] [Author]

RE: 1997 AISC seismic - IBC seismic design category D - OBF brac e connections - column strength

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Title: RE: 1997 AISC seismic - IBC seismic design category D - OBF brace connections - column strength
Charlie:
 
 
While I got you on the line.   1997 UBC Table 16-N Bearing wall systems has "Braced frames where the bracing carries gravity loads". While IBC Table 1617.6 Bearing wall systems has "ordinary braced frames".

Is the IBC saying that if the braced frame carries gravity loads it cannot be a special concentrically braced frame and that an ordinary braced frame that carries gravity load must be designed with R=4 instead of R=5? This would be a big change from the UBC which said if the "bracing carries gravity loads".

Thanks,

Scott M Haan P.E.
Plan Review Engineer
Building Safety Division http://www.muni.org/building
Development Services Department
Municipality of Anchorage
phone:907-343-8183  fax:907-249-7399
mailto:haansm(--nospam--at)ci.anchorage.ak.us

-----Original Message-----
From: Charlie Carter [mailto:carter(--nospam--at)aiscmail.com]
Sent: Wednesday, May 02, 2001 6:56 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: 1997 AISC seismic - IBC seismic design category D - OBF brac e connections - column strength

>Is [the lack of a requirement to consider orthogonal effects] an
>oversight in the conversion to the IBC from the UBC, that the AISC
>[Seismic] Provisions [were not amended to require such consideration]?

I'm seeking a more formal answer to your question, but in the mean time I can tell you that requirements regarding orthogonal effects were considered in the development of the AISC Seismic Provisions, but intentionally written as you read them in the AISC Seismic Provisions. That is, the non-requirement is intentional and, I believe, was intentionally carried in similar fashion forward into the IBC by reference. If I remember correctly, the AISC Committee on Specifications decided that consideration of orthogonal effects should be left to the judgement of the designer. I'll be back later with a more official response when I have it.

Charlie