BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
(OP)
IF YOU HAVE A BRACE FRAME BEAM WITH AXIAL LOAD BRACED AT 2'-0" O/C AT THE TOP FLANGE, WOULD YOU CONSIDER IT BRACED ABOUT THE Y AXIS FOR AN LY=24" OR USE THE ENTIRE LENGTH CONSERVATIVELY IN THE Y AXIS?






RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
I highly recommend attending the "Basic Design for Stability - Columns and Frames" seminar offered through AISC. I just went to the AISC web site and looks like you missed this round of seminars but keep your eyes peeled.
Maybe you can find someone who has notes from this seminar. Good luck.
RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
Another good reference for axial-torsional buckling with a more in-depth discussion is Guide to Stability Design Criteria for Metal Structures, edited by Galambos.
RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
Following the path of this force you will find that it will make My on the last column of your building which is connected to this brace so you must put in mind this considerations.
RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
Actually, if this is a discrete brace system you could actually use 1%, however, stiffness of the brace must be adequate. Again, I refer you to the seminar I mentioned above. Hopefully, we can wipe out the design of braces using strength only in our life time.
RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
My answer would be NO. I would not use an Ly of 24" unless both flanges are braced or the brace extends at least 2/3 of the depth of the beam. As Dozer noted above, if the brace does not provide torsional restraint, then it is not adequate.
On the other issue raised, I have always used the strength method (2% rule) as a basis for my bracing design. Dozer, Am I to understand that this is no longer acceptable? I have read the "Bracing for Stability" ourse by Yura and Helwig but never did come away with an effective way to determine the stiffness or stiffness limits of a brace (discrete or othwerwise). Do you have any info or resource that could better clarify this question for me?
Thanks.
JS.
RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
I have "Bracing for Stability" dated Feb 2001. This was the booklet that came with the seminar at this time. Within this booklet is a paper titled "Bracing for Stability - State of the Art", by Joseph Yura, rev'd 11/7/99. This gives stength and stiffness requirements for four different types of brace systems.
RE: BRACED FRAME BEAM UNBRACED LENGTH FO AXIAL
For your other beam with the roof trusses at the top chord, I would also say no it is not adequately braced for axial loading. If you could also attach kickers from the truss to the bottom flange of the beam, and the trusses are adequate to take the brace load, then I would consider the beam braced.