Sp coeficient is Z factor of 10th Ed API 650

[inammanj123]

Hi,

In API 650 if seismic zone factor is given(Z factor of 10th Ed), Can we use this value as Sp in 11th Ed onwards??

for example seismic zone factor is 0.075, so can i use Sp as 0.075??


Thank and Regards,
Inam

 

[mariog123]

Yes, see the definition under E.2.2 Notations
SP= Design level peak ground acceleration parameter for sites not addressed by ASCE methods. [See EC Example Problem 2 when using “Z” factor from earlier editions of API 650 and UBC. Since 475 years recurrence interval is basis of this peak ground acceleration, Q = 1.0 (no scaling).]

Note also that E.4.6.1 Spectral Acceleration Coefficients states that "For sites where only the peak ground acceleration is defined, substitute SP for S0 in Equations E.4.6.1-1 through E.4.6.2-1."

You may conclude that SP=S0=Z for non-ASCE sites, ground acceleration defined for 475 years recurrence interval.