Hello Leonard
Information (non FEA) for this analysis is difficult to come by. We have carried out a search, and so far have come up blank. However, there is a suggested method in the Dennis Moss book in the back where it discusses local loads on spherical shells. It uses the method set out in the British Code PD 5500 in its Annex G. This seems to be the way to go for determining the local stresses in the shell in the region of the leg attachment.
Because of the liquid load, it would appear that a bending moment will exist in the waist of the sphere between the leg supports. If the effective portion of the shell can be determined (using the Sqrt(R.t) method), it might be possible to analyse the sphere in that region as an encastre beam, but I am not sure of the validity of this approach.
An excellent programme for performing this analysis is FE Pipe, but the downside might be the cost.
ASME VIII Division 2 gives a suggestion using a unit force 'F', but it seems to me that this is not very helpful, as the real problem is the localised nature of the loading, and the tendency of the waist of the sphere to sag.
If anyone has any information to send to the forum, it would be very much appreciated.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM