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RE: Ordinary moment connections - pre-engineered metal buildings

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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.