r value for drift calcs

huangyhg

r value for drift calcs
i am working on a bridge.  the framing in the short direction is a steel moment frame.  this sits on a concrete girder and concrete pier (forming a t on which the moment frame sits) at each end.  i was using and r value of 2.2 per 1997 ubc for cantilevered column structures.  can i use this same value when calculating the inelastic displacement, dm = 0.7*r*ds?  or do i need to use the r value for a steel moment frame, r = 8.5?
check out our whitepaper library.
use the same r factor you used to calculate your forces.