Civil Engineering/Engineering Terms
QUESTION: What is the difference between this equation used by the NSCP from the standard IBC equations?
Is V measured in kips?
V = Z I C W / Rw
Z=seismic zone factor
I= Occupancy importance
C= base shear coefficient
W=total dead load
Rw= moment resisting frame
ANSWER: Dear Franco
Please write me back the IBC relationship. The difference is basically On method of design, working stress ( in this relationship) and ultimate design ( I guess IBC follow this one). Then usually you see a factor 1.4 to 1.6 difference between them.
The units is dependent of unit of W in both codes.
---------- FOLLOW-UP ----------
QUESTION: IBC standard equation for base shear:
V = Cs W
W = effective seismic weight
Cs = Seismic response coefficient
R= response modification factor
Ie= importance factor
for T<=Tl (period and long transitional period)
As I stated in my last letter , The difference is in R and Rw factor. In IBC you have smaller R which lead to ultimate design forces but in the some codes they use Rw which is bigger in quantity and lead to allowable stress design. The difference between R and Rw is almost the factor of safety say 1.5 to 2