qualifications for a braced compression flange

huangyhg

qualifications for a braced compression flange
i have a design where 4 inch joists frame into the backside of a 12 inch deep c-channel.  however, the top of the 4inch joists are 2.25 inches below the top of the c-channel (therefore not directly offering support to the top flange).  i have opted to put in a flange stiffener at this location.  my engineering judgment wants to allow me to qualify this location as a place of compression (top) flange bracing for the c-channel.  however, i have failed to produce any resource that allows me to actually calculate this assumption.  can anyone give me advise on how to confirm this assumption? (calculation techniques
or personal engineering judgment are both appreciated)
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if you're in the us check the aisc spec.  it contains information for quantifying and checking stability bracing.
thanks for quick response.  i am in the us, but the structure is actually aluminum.  however, i am comfortable using the approach aisc takes in defining lateral bracing as applicable to aluminum design.  i reviewed the aisc (appendix 6) very helpful.  i also did a key word search with your suggestion and found this鈥?also very helpful.
aisc faq:  what constitutes a lateral brace for a beam?