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RE: Ordinary moment connections - pre-engineered metal buildings

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I agree you can use ordinary moment frames per the code limitations in
Seismic Design Category D.  The question is not whether they can be
used, the question is whether the connections can be designed for the
special load combinations and not the internal forces specifically
prescribed in AISC Seismic.

-----Original Message-----
From: Scott, William N. [mailto:William.Scott(--nospam--at)veco.com] 
Sent: Monday, April 05, 2004 4:26 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Ordinary moment connections - pre-engineered metal
buildings


The ICC IBC2003, Table 9.5.2.2 allows Steel OMF and IMF with endplate
connections for SDC D, E, and F per footnote "h" and allows OMF per
footnote "i" if the dead load of the roof is less than 15 psf.

-----Original Message-----
From: Haan, Scott M. [mailto:HaanSM(--nospam--at)ci.anchorage.ak.us]
Sent: Monday, April 05, 2004 3:06 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Ordinary moment connections - pre-engineered metal
buildings


It is in the 97 UBC but it is not in the 2000 IBC or AISC Seismic.  I
guess many pre-engineered metal building manufacturers are designing
OMRF connections this way in Seismic Design Category D.

-----Original Message-----
From: Jim Persing [mailto:jpersing(--nospam--at)FHOARCH.COM] 
Sent: Monday, April 05, 2004 2:37 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Ordinary moment connections - pre-engineered metal
buildings


I think that the omega level forces come directly from the 97 UBC,
Section 2213.6, para 2.
 
Jim Persing

-----Original Message-----
From: Carter, Charlie [mailto:carter(--nospam--at)aisc.org]
Sent: Monday, April 05, 2004 2:38 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: Ordinary moment connections - pre-engineered metal
buildings



AISC Design Guide 4 on end-plate moment connections is being typeset
now. It covers end-plates in SMF, primarily. I know of no basis for the
assertion that there is permission somewhere to design metal building
OMFs for omega-level forces and forget the member strength development
requirements. But I don't know everything, so I will check around and
see what I can find.

 

Charlie

 

 


  _____  


From: Haan, Scott M. [mailto:HaanSM(--nospam--at)ci.anchorage.ak.us] 
Sent: Monday, April 05, 2004 4:11 PM
To: seaint(--nospam--at)seaint.org
Subject: Ordinary moment connections - pre-engineered metal buildings

 

Someone has indicated to me that the metal building industry is not
designing ordinary moment connections per the exact wording in AISC
Seismic section 11.2a.  I have not checked if this has been discussed on
the list before.

American Institute of Steel Construction [AISC] AISC Seismic Provisions
Section 11.2a indicates that fully restrained ordinary moment
connections need to be designed for a flexural strength Mu that is at
least equal to 1.1*Ry*Mp of the beam or the maximum force that can be
delivered to the connection by the system or need to demonstrate an
inelastic rotation of at
least .01 radians per AISC Seismic Appendix S and Section 9.2a.   The
special load combinations incorporating the over strength factor are
meant to approximate the maximum force that can be delivered to an
element by the system.  

It is come to my attention that it is the metal building industry
standard practice to design ordinary moment connections for the special
load combinations and not the options specifically written in the code:
tested or 1.1*Ry*Mp or maximum load that can be delivered to the system.
The Metal Building Manufacturer's Association [MBMA] in conjunction with
the AISC are in the process of drafting the "MBMA Seismic Design Guide
for Metal Buildings" which will allow ordinary moment connections to be
designed for the special load combinations.

Are other jurisdictions allowing special load combinations to design
ordinary moment connections as an approximation of the maximum load that
can be delivered to the connection by the system?

Why aren't the AISC Seismic Provisions written to allow the special load
combinations specifically for ordinary moment connections?  

Are the AISC Seismic Provisions going to be modified to specifically
allow this method of determining the internal forces for designing
ordinary moment connections?

  

 

Scott M. Haan P.E. 
Chief of Building Inspections 

Municipality of Anchorage 
Development Services  Department 
Mission Statement:  Guide safe construction and responsible development
for the community. 







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