Define response spectrum cases

[h-badawy]

Dear experts

Regarding to the scale factor of the respnse spectrum function as per UBC-97 item 1631.2 and 1631.5.4 the elastic response spectrum should be divided by (R/g) but in ASCE-05 item 12.9.2 the elastic response spectrum should be divided BY (R/I),and the different between two values is very high for example
UBC value =4.5/9.81 =0.459
ASCE value =4.5/1.2 =3.75
My question is there any item in ASCE code mentioned that we should take the effect of the (g) acceleration in the calculation of the response spectrum function .

 

[wannabeSE]

In ASCE 7-05, the spectral acceleration units are in g's per figure 11.4-1. So you need to multiply Sa by g to get an acceleration in units of length/time².