Subject: Update on Steel Moment Frame Publications
From: "Ron O. Hamburger" <ROH(--nospam--at)eqe.com>
Date: Thu, 25 May 2000 07:53:18 -0700
In several recent posts,the question of how to design steel moment frame
connectiosn has been raised, with advice sugested. Currently, the UBC requires
that connections for SMF systems be demonstrated by test to be capable of
developing plastic rotation demands of 0.03 radians. The AISC Seismic
Specification, FEMA 267, FEMA 267a and FEMA 267b provide information on how to
conduct such tests and several different types of connections that have been
Today, most engineers use a connection that has already been tested by others.
This is acceptable, as long as the member sizes in the test specimen were
reasonably representative of those being incorporated in the project. Again,
the FEMA267 seris provides guidanceon "how similar" a test should be to a design
Most designs today are using one of the following connection types:
1- Reduceed Beam Section (or dog bone)
2- Proprietary Slotted Web Connection (SSDA of Southern California - licensor)
3- Propritetary Sideplate Connection (Sideplate of Southern California -
4- Cover plated connections
Summary data on past testing of RBS and coverplate connections can be found on
the SAC web site. The licensors of proprietary connections will provide their
own qualification data, when a license is purchased.
In about 1 month, the SAC project will transmit to the FEMA 350, 351, 352 and
353 documents to FEMA for publication. They should be available, free of
charge, by the end of summer. These publications will provide design
procedures, standard details and specifications for a series of prequalified
connections that can be used on projects, within their prequalification limits,
without further substantiating tests. The prequalified connections are:
Welded Unreinforced Flange - Bolted Web ( a connection similar to the "old
warhorse pre-Northridge Connection) but constructed with better control of
materials and workmanship. It is approved for application to OMF.
Welded Unreinforced Flange - Welded Web ( similar to the above, but with a full
pen welded beam web to column connection). This is approved for SMF service.
However, field welding and quality assurance requirements are extensive.
Reduced Beam Section (the dog bone) - approved for SMF
Free Flange - a vesion of the Welded Unreinforced Flange connection in which a
large cope is made in the beam web, and a heavy shear connection plate is used
to transfer flexural and shear stresses to teh column. It is approved for SMF
Welded Flange Plate - a type of cover plated connecttion in whicht the beam
flanges weld to cover plates, that then weld to teh column. Approved for SMF
Bolted End Plate - similar to the Welded Flange plate, but attachment to the
beam is made with high strength bolts. Approved for SMF service.
End Plate - available in stiffened an unstiffened versions. The beam shop welds
to an end plate (similar to a bse plate connection on a column) The end plate
then field bolts to the column. Approved for SMF service.
Bolted T - a type of PR connection in which split tees are used as bolted
connectors between the beam and column. Also approved for SMF service.