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Re: [SEAOC] Steel Moment Connections with Cover Plates[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)seaoc.org
- Subject: Re: [SEAOC] Steel Moment Connections with Cover Plates
- From: "Ron Hamburger" <roh(--nospam--at)eqe.com>
- Date: Wed, 27 Mar 1996 13:37:50 PST
- Priority: normal
On3/27 - Anthony Tarek wrote: > This question is in regard to steel moment connections with cover plates. > Most of the test conditions and published results (i.e FEMA guidelines) > that I have seen have a continuous column with a beam butting against it. > If a beam is continuous over the column is it necessary to use cover plates > on the beam? And if so, does this effectively shift the plastic hinge away > from the connection. > Another scenario is to place cover plates at the column flanges instead of > beam flanges. Does this strengthen or adversely undermine the column > connection? > Response: Running the beam through the column may be an effective solution in some cases. This would not shift the plastic hinge away from the joint. You would still have a plastic hinge forming at the face of the column, where presumably, you would have a joint in the column flange, however, you would probably not be placing this welded joint into a plastified condition, so long as the column is of adequate strength relative to the beam to assure that plastic action occurs in the beam. Please note however, that you introduce a discontinuity (the welded joint) into the column at a point of high stress, which is genearlly not good practice. Essentially, you are introducing a column splice at the point of highest stress. While this is not prohibited, it can result in fracture initiation in the column, if the weld is of inadequate toughness and incorporates sufficiently large flaws or discontinuities. Full penetration welds should always be specified for this joint, not partial penetration, as the partial penetration weld can easily initiate fracture under high stress demand. You may be interested to note that a detail somewhat similar to this is quite common in Japan. A number of buidlings using this detail in Kobe experienced fracture at the column to girder splice connection, as a result of either the use of fillet welds for this joint, partial penetration welds, or welds of inadequate toughness. If this detail is attempted, it would be a good idea to perform some qualitifcation testing, as I am not aware of any available data on the performance of this connection type. Also, the full pen welds of the column flanges to the beam should incorporate notch tough weld metal (20 ft-lbs at 0deg. F) as suggested by the SAC Interim Guidelines (FEMA-267) for critical joints. Regards, Ron Hamburger Project Director for Product Development SAC Steel Project Ronald O. Hamburger, SE Regional Manager EQE International, Inc. San Francisco, California ...
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