Seismic design as per API650

[Anand23404]

Dear fellows!
Greetings!

please help me out the problem i am facing now.My quesry is about Equation E-4.6.1-1 of API 650, 2013. it says '...However, Ai>= 0.007and for S1> 0.6...Ai> 0.5S1.(I/Rwi)= 0.625Sp(I/Rwi)"

Here, please be noted that i am getting S1 value which is greater than 0.6 and Ai value is greater than 0.007.

Eq.4.6.1-1 yields higher value than Eq.4.6.1-3.

Now please elaborate as when I should use equation E.4.6.1-1 and E.4.6.1-3??

regards

 

[mariog123]

IMO, it is a simple math language

Impulsive spectral acceleration parameter, Ai:
[Ai=....] (E.4.6.1-1)
However, Ai ≥ 0.007 (E.4.6.1-2)
and, for S1 ≥ 0.6:
[Ai≥....] (E.4.6.1-3)

I understand that, for all cases, Ai must be the greater of the value calculated by E.4.6.1-1 and 0.007.
For cases when S1≥0.6, Ai must be the greater of the value calculated by E.4.6.1-1 and 0.007 and the value calculated by E.4.6.1-3