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Re: Knee Braced Frame-Effective Column Length[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: Re: Knee Braced Frame-Effective Column Length
- From: "Michael Donoghue" <cmd(--nospam--at)ibm.net>
- Date: Tue, 9 Mar 1999 17:11:05 -0600
James; Could you not look at the knee brace as a moment couple just as you have in a moment connection? Wouldn't that act as an effective moment connection (albiet a deep one) for the column? cmd -----Original Message----- From: James F Fulton <James_F_Fulton(--nospam--at)RohmHaas.Com> To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org> Date: Tuesday, March 09, 1999 4:52 PM Subject: Knee Braced Frame-Effective Column Length >Consider a 5 story bldg. where all levels above the first elevated floor are >X braced, but the first elevated floor level has knee braces from the girders >to the columns below. All the girders are simply connected to the columns. >Therefore, the frame up to the first level has sidesway, which incidentally >makes up most of the lateral deflection of the levels above under lateral >load. I consider the frame up to the first level to be an "unbraced frame" >because of the sidesway, even though it has knee braces, and K=1 does not >apply here. How does one determine the "K" value and corresponding effective >length of these first level columns ? The "sidesway uninhibited" curves in >the ASD (9th) or LRFD (2nd) are based on *rigid* connections between the >girders and columns such that the girders provide rotational restraint to the >columns. But in my case the girders are pin connected to the columns, so in >theory rotational restraint is absent. I would appreciate any insight to this >problem. Thanks. > > >
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