Brace Length Reduction due to Gusset Plate (SCBF) 2

[Gumpmaster]

Has anyone seen any references that deal with the unbraced length of braces in special concentric braced frames. Specifically, I'm looking for some sort of reduction in the unbraced length due to the gusset plate bracing the end of the brace member, or the gusset providing some sort of fixity so I can adjust my K factor.

P.S. I'm using HSS braces.

Thanks.

 

[JAE]

Is this in a significant seismic area?

 

[Gumpmaster]

SDC E, pretty significant.

 

[csd72]

Since the gusset is more flexible than the brace, I wouldnt use K any less than 1.

Check out

http://www.aisc.org/Content/ContentGroups/Documents/Connections_IV_Proceedings/307.pdf

http://www.aisc.org/Content/ContentGroups/Documents/Steel_Tips1/144_dec_98.pdf

http://www.isope.org/publications/journals/ijope-10-4/abst-10-4-p292-RSP-14-Ariyoshi.pdf

 

[mrMikee]

csd72,

That looks like some good information. I'm printing them out right now, these need to go into my files.

Thanks,
-Mike

 

[JAE]

The second link (nice work csd72) indicates what I was heading towards in my question above. AISC indicates that rigid end connections absorb more energy that "pinned" ends at braces as this requires three plastic hinges to form instead of one.

However, many braces are designed as pinned and you have to watch out that you detail the gusset to allow out-of-plane buckling to occur - See Figure 2.8 in the Steel Tips link (second link) above.