API 650 appx. E

[ird192]

trying to determine moment of tank footing , ist timer , associate ran his software which I reviewed , I noticed his system loaded a value for Ss & S1 , which was used to generate a value for SDs and SD1, which in turn is used to generate a value for Ai in equation E4.6.1-1 and Ac in E4.6.1-4 . It seems the value of Ai has a major impact on the moment calculations. my question after all of the above is I can look on USGS and get a value for SDs & SD1 for my specific site , when I do that I get different values for Ai and Ac which in turn give me higher moment values , so am I wrong in used USGS values for SDs and SD1 , hope this makes sense

 

[JStephen]

Check if both are using the same Site Class. Difference in site class will then use different Fa and Fv, giving you different seismic coefficients.
Check if both are using the same edition of ASCE 7 data. If there is a governing building code, then it will generally say which edition of ASCE 7 is to be used (I think Chapter 35 in the IBC codes lists all the references, along with the year.)
And if both of those are the same, I think there are still some minor discrepancies in the Fa and Fv factors used.

Edit: See:

https://www.skghoshassociates.com/b...about-the-new-site-coefficients-in-asce-7-16/

https://www.skghoshassociates.com/blog/new-site-coefficients-in-asce-7-16-2/

 

[HTURKAK]

I would like to remind that Fa and Fv values tabulated at tables E1 and E2 are 1.0 for site class B. You are expected to choose the relevant Fa and Fv for your specific site soil conditions..



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