Seismic Force-Resisting System?
Seismic Force-Resisting System?
(OP)
I am doing ASCE 7-05 seismic calculations of cooling tower support steel structure (see attachment) and I am not sure what seismic force-resisting system it is. Ordinary steel concentrically braced frame (R=3.25) or Special steel concentrically braced frame (R=6) or Steel system not specifically detailed for seismic resistance (R=3)? Seismic design category is "D". Thank you,






RE: Seismic Force-Resisting System?
RE: Seismic Force-Resisting System?
Looks like you have some sort of an eccentric braced frame. Since you are Cat. D you should be using AISC 341, see ASCE 7-05, Section 14.1.3. I would look through AISC 341 and modify your bracing to match one of their braced systems, and design accordingly.
RE: Seismic Force-Resisting System?
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RE: Seismic Force-Resisting System?
According to AISC 341-05 Commentary C11.1 OMF Knee-Brace Systems – I can design tower framing in one direction as ordinary moment frames with R=3.5. How about other direction? Any suggestions?