Hi
I've been running tank 3.10 and according to the report for the check of the wind overturning stability (by the way i believe it is acc.to section 5.11 and not 3.11 as it says) the report mentions that anchors are required.When I see the anchor bolts details report it says that anchorage is not required.Should i include anchorage in my design?
Another thing is that when i design the tank with rafter supported cone it doesnt require anchorage (based to anchor bolts details report).For every other type of roof (except open top of course) anchorage is required.Is this possible or there is something that i might not doing right?
Thank you in advance.

No you're not doing anything wrong. The problem here is that the various sections of the API-650 Code were developed independently. As a consequence, sometimes the various sections lead to conflicting conclusions.

Thank you for your reply.So in that case should i have the tank anchored for overturning stability reasons?

Another thing i want to ask you is about seismic design data input.I know the peak ground acceleration Sp of the area where the tank will be located (site not defined by ASCE 7 method).In the following data requesting by TANK if I use only the Sp value will i get adequate results or do I have to fill any other parameter of the ones mentioned below.

Mapped maximum earthquake for short periods (Ss) ...... 0.00000
Mapped maximum earthquake for 1 sec periods (S1) ...... 0.00000
Mapped maximum earthquake for 0 sec period (S0) ...... 0.00000
Non-ASCE peak ground acceleration (Sp) ................ 0.00000
ASCE short period design acceleration parameter (SDS).. 0.00000
--- Site Specific Data ---
Spectral acceleation parameter at 0 period (Sa0*) ..... 0.00000
Spectral acceleation parameter at any period (Sa*) .... 0.00000

Yes I would anchor the tank - better safe than sorry.

You should be ok with Sp.