huangyhg

r=3
in designing steel for seismic forces, where does it say if you use r=3 or less you dont need to design with the special seismic provisions? aisc? fema350?
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end of table 1617.6 of ibc.
part 'e' of inverted pendulum systems.
why it is under inverted pendulum systems, i have no clue, but this is what the bldg. departments are going by (so i have been told).
ibc section 2212.1.1 is the section you're looking for. it says for structures in seismic design category a, b or c you can use the r of 3, and not have to conform to the aisc seismic provisions. sdc d, e & f is required to conform per section 2212.1.2
2212.1.1 is restating what the table gives you.
as i understand it, you still have to use the omega and cd values that is at the end of the table i mentioned as well. you can't use r=3 and then whatever omega and cd values you find that match your actual system from the table.
re: ibc table 1617.6
ibc misprinted the early versions of the code putting structural steel not detailed for seismic... under item 6.
it is now separated into its own category, item 7.

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