SCBF Column Design Query

[coolad2007]

Hi all,

I am designing 8 story industrial steel structure with SCBF system. Its a pretty symmetrical square box kind of structure and with loads at different level. I ran it in Etabs and wanted to cross check results manually for column design. I wanted to know if the columns whihc are also the part of SCBF would need to be designed considering overstrength factor or not, for amplified loads. Or does Rho apply in such laod combinations.

Thanks in advance

 

[SethGuthrie]

The columns in SCBF need to be checked for the standard form load combinations with rho factors included, not the amplified seismic combos with Omega. But, the connections are designed for the higher level seismic loads (e.g. column splices) or the capacity of the member (e.g. gussets).

 

[BAretired]

Okay, I give up...what is SCBF? I'm pretty sure you are not referring to the Sacred Cat of Burma Fanciers or the Scottish Concert Band Festival.

BA

 

[SethGuthrie]

Special Concentrically Braced Frame was my assumption.

 

[shin25]

You should look into AISC seismic design manual (aisc 341 if I am right).

Rho is related to redundancy in the system and apply to the lateral force resisting system as a whole and may not apply to system where rho is 1. For these systems where rho is 1, enough capacity still remains in case a member in the force resisting were to fail.

The method for designing columns for scbf should be related to maximum expected ultimate capacity of the braces which may be similar to system over strength or global over turning capacity of the foundations.

 

[shin25]

Plasticity in scbf is achieved thru yielding of the braces only where columns must remain elastic. This is why columns must be designed for forces larger than capacity of braces.