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RE: RISA to sway or not to sway

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If you’re modeling in-plane loading only in RISA-2D, then this is a fine application for the program.  To account for the different levels of bracing, all you need to do is tell the program what unbraced lengths and K values would be appropriate to use for the allowable stress calculations.  This can be as simple as double-clicking the member of interest (which brings up the Member info dialog) and then selecting the design tab.  You tell us what the in-plane buckling length for that member is and what the out-of-plane buckling length for that member is and we’ll do the code check.  If you leave these entries blank, then the program will assume the full member length.  Also, keep in mind that you might have to enter in a higher K value based on the support and sway. 




Josh Plummer, SE

RISA Technologies


From: Sharon [mailto:sharon(--nospam--at)]
Sent: Wednesday, September 06, 2006 4:31 PM
To: seaint(--nospam--at)
Subject: RISA to sway or not to sway




I have modeled a 2-story, 4-bay (60’ long) moment frame in RISA-2D.  The frame is supported out-of-plane completely at the roof level but only at the 2 exterior columns at the floor level.


What is the best way to model the 3 interior columns and the floor level beams?




Sharon Robertson, P.E.

Arcon Engineers 
5625 Ruffin Rd, Ste 130 
San Diego, CA  92123
858/503-7858 fax

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