Knee Brace as a substitute for X-Bracing 1

[Ipetu]

I am designing a rectangular platform for an industrial application. All four bays in the vertical plane were provided with diagonal x-bracing. Due to clearance requirements the diagonal x-bracing is not acceptable. Can the x-bracing be replaced with knee braces? Or are knee braces together with rigid moment connections required? Thanks in advance.

 

[Ron]

I have done this before where equipment shelters needed clearance, so x-bracing was out. Knee braces should work well unless you are in an extremely high wind area.

 

[asixth]

Knee braces are common for structures with a small 'racking' force. Your frame may become more flexible because of the eccentricity of the bracing.

 

[haynewp]

You are switching from concentrically braced frames to knee braced frames (ordinary moment frames in AISC 341-05) so there are different seismic limitations under this document. I don't what code you are under.

 

[Einsteim]

Yes, knee braces are acceptable and practical. You may need stiffer columns and/or beams to limit lateral deflection. X-braces are used because they are more efficient that knee braces, but knee braces are common. Be sure to check the columns and beams for the added moment you will impose on them. Also, we typically round the code required lateral load up to be conservative.