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RE: Construction Type

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These are referring to the types of construction permitted in the AISC Specification, though I am not sure why MASTERSPEC has them organized as they do. And, there is a mix of terms between ASD (Type 1, 2, and 3) and LRFD (Type FR, PR, and Simple) from Specifications before the 2005 AISC Specification.


Type 1 and FR mean fully restrained (rigid) moment connection. Type 2 and Simple mean simple shear connection. Type 3 and PR mean partially restrained (semi-rigid) moment connection. In the 2005 AISC Specification, the terms FR, Simple, and PR are used.


As far as how these apply to the different types of buildings, it depends what connections you are using in those buildings. For moment frames, the lateral system usually has FR moment connections, though I have seen a few with PR moment connections. The gravity system in moment frames is usually Simple. In braced frames and frames with shear walls, the connections are usually Simple throughout, though the terms get a little stretched when trying to call a brace connection transmitting axial force through a gusset “Simple”.


You also mentioned FMC in your question. These are flexible moment connections – the age-old “type 2 with wind” connections popularized originally by Bob Disque and recently updated for modern practice by Lou Geschwindner and Bob Disque in a paper in the AISC Engineering Journal. The title is “Flexible Moment Connections for Unbraced Frames Subject to Lateral Forces--A Return to Simplicity”. It is available as a free download for members of AISC here: (search on “Disque”, scroll down, and look for the above title in the list that is generated)


Or, here is the direct link to the file:


You can also find Bob’s 1964 and 1975 papers on the subject if you want to read the historic origins of this type of design.


Hope this helps.




From: Sklar, Mitch [mailto:mitch.sklar(--nospam--at)]
Sent: Wednesday, April 26, 2006 11:03 AM
To: seaint(--nospam--at)
Subject: Construction Type


The following  construction types appear in section 05120 of the masterspec.


B. Construction: Type FR, fully restrained; Type 2, simple framing.

C. Construction: Type PR, partially / FR, fully restrained.

D. Construction: Type 1, rigid frame. / 2, simple framing. / 3, semirigid framing.

Can I get a consensus on the definition of each type and what kind of buildings they would typically apply to? Such as a two story steel framed structure w/PR-FMC connections or a 1 story masonry shear wall structure with CFMF trusses.