Frame Sidesway - braced or unbraced?

[slapjack]

I'm running a computer model of a 5 story office structure (RAM). The lateral force resisting system is made up of 2 L-shaped braced fames located on opposite corners of the structure. Each floor will consist of a 3" concrete slab (rigid). With this configuration, I would assume that I should consider my frames braced against sidesway for analysis- correct?

 

[twinnell]

It depends on what type of bracing you are using. If you are using full concentric diagonal bracing, then yes you have braced frames. If you are using eccentric braced frames where the brace work point does not line up with both the column and beam centerlines, then you have to determine the displacement of the frame to be able to determine whether it is considered braced or not.

 

[slapjack]

I actually do have eccentric braced frames in one direction... concentric in the other. Can you give me a little more information on how I can determine if the frames are considered braced or not based on the displacement? Is there a section of the building code or steel manual that tells how this can be determined?

 

[twinnell]

I can't find my reference material. It was a document from RAM. Call Seth Guthrie, of RAM, and ask him to send you the document on braced and unbraced frames. He will most likely answer when you call tech support. Essentially, if you have an eccentric brace you can consider it a braced frame system until it deflects so much that it is unbraced. The document tells you where to look for that deflection criteria.

 

[slapjack]

I contacted Seth at RAM and all they have to offer is exactly what is printed in the manual. Anyone else have any info or suggestions on where to find more information on this topic?