Scott: Here in Southern California we use
an exception to the UBC. 1999 SEA California Recommended
Lateral Force Requirements and Commentary
Sec 105.4.4 Combinations
Along the Same Axes
Exception: For light frame buildings in occupancy
groups 4 & 5 and of two stories or less in height, the lateral force
resisting elements are permitted to be designed using the least value of R for
the different structural systems found on each independent line of resistance.
The value of R used for the design of diaphragms for a given direction
of loading in such structures shall not be greater than the least value used
for any of the systems in that same direction.
Johnson & Nielsen Associates Palm Springs, CA