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Re: moment frame conn. per FEMA[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaoc(--nospam--at)seaoc.org
- Subject: Re: moment frame conn. per FEMA
- From: Parkerres <Parkerres(--nospam--at)aol.com>
- Date: Wed, 13 May 1998 11:22:07 EDT
We design many small OMRF frames here in LA City and use the following guidelines to get around the fancy connection design. The City lets you use a Rw= 2.67 for connection design in OMRF's with flexible diaphragms. This is equivalent to Rw / (3Rw/8) when Rw=6 for OMRF. To accomodate this requirement, we run our frames in the computer using a scaling factor of 2.25 (3Rw/8) times the seismic forces on the members. We check the members with a 1.33 increase as allowed per Code. If the entire member works for this greatly increased force, we then assume that a typical, pre- Northridge flange-welded, web-bolted connection is adequate without cover plates, etc. We then check the frame for drift without the 2.25 scaling factor. Since drift governs anyway in many cases, we are not paying any premium in the steel cost and are saving in the connection cost. Plus it greatly simplifies the analysis for a small frame. Good luck, Bruce Resnick, SE Parker Resnick Str. Eng.
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