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RE: Joist Girder Moment Frames?

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Many years ago I designed several projects utilizing joist girders in moment frames in the Kansas City area.  The problem was that when you assumed the joist girder as a rigid element, the end connections were expensive.  Using the connection design concepts of semi rigid connections as developed in Blodgett's "Design of Welded Structures" in combination with the concept of wind flexible connections, we constructed many buildings.  The moment connection plate was tapered and had an unwelded area to allow for ductile yielding.

The basic concept was to allow the moment connection plate to yield under gravity loading, but the connection would have sufficient strength to resist applied lateral moment loads.  The applied moment on the joist girder was predicated on the strength of the yielded connection plus a safety factor to assure that yielding took place in the connection plate. The gravity connection for the joist girder was independent of the moment connection plate and allowed yielding under moment loads without compromising the gravity connection.

Vulcraft was the supplier on these projects.  The projects constructed in this fashion included office buildings and warehouses.

To design this same type of system today to resist seismic loads would probably require testing of a full scale model.  I do not believe that this has ever bee done.  I believe that it would perform very well under seismic loading.  It is essentially the "seismic fuse" concept.

Harold Sprague
Krawinkler, Luth & Assoc.
4412 W. Eisenhower Blvd.
Loveland, CO 80537
Voice: 970 667-2426
Fax: 970 667-2493
Email: hsprague(--nospam--at)

-----Original Message-----
From:	Chris Palmateer [SMTP:chrisp(--nospam--at)]
Sent:	Thursday, February 12, 1998 11:34 PM
To:	seaoc(--nospam--at)
Subject:	Joist Girder Moment Frames?

I'm curious,  does anyone have any experience with utilizing open web steel joist girders as part of the lateral system in buildings?  Vulcraft will design the girders for the loading specified on the