API 650 11th Edition - Seismic Anchorage
API 650 11th Edition - Seismic Anchorage
(OP)
Hello,
API 650, 11th Edition, Section E.6.2.1.2 has equations for seismic anchorage. However, Section 5.12 in combination with Table 5-21 has equations for seismic anchorage as well.
The question is, how have you approached the two conflicting equations? Do you look at both and use the most conservative number? Or...?
Also, when a tank is not required to have seismic anchorage (J <= 0.785), but anchorage is required for wind, do we need to look at the seismic uplift equation in Table 5-21? Or do we just look at the equations that are requiring anchorage (i.e. wind in this case)?
Please help!
Thanks!
API 650, 11th Edition, Section E.6.2.1.2 has equations for seismic anchorage. However, Section 5.12 in combination with Table 5-21 has equations for seismic anchorage as well.
The question is, how have you approached the two conflicting equations? Do you look at both and use the most conservative number? Or...?
Also, when a tank is not required to have seismic anchorage (J <= 0.785), but anchorage is required for wind, do we need to look at the seismic uplift equation in Table 5-21? Or do we just look at the equations that are requiring anchorage (i.e. wind in this case)?
Please help!
Thanks!





RE: API 650 11th Edition - Seismic Anchorage
You can download a draft version of Rev. 1 from API's website and see if any of this is proposed for update.
Generally, the equations should give similar answers. The anchor uplift is just based on Mc/I - P/A cast into various forms.
If a tank requires anchors for wind or pressure, you should still size the anchors and chairs for seismic load, even if seismic load by itself would not require anchors.
RE: API 650 11th Edition - Seismic Anchorage
Joe Tank