Hi all,

I'm trying to find the maximum allowable pressure inside a rectangular storage tank filled with dielectric oil. The tank consists of 6 aluminium 6061-T6 plates which are connected with corner joint fillet welds. I assume that the welds will fail first, which will determine the maximum allowable pressure.

Which stresses do I add together in order to get the maximum principle stress in the weld? I made a calculation for the shear stresses in the weld using the Huber-Hencky equation and I calculated stresses in the long edges of the side plate and top plate (assuming these plates would be clamped on all edges). I took an internal pressure value of 4.5 bar (0.45 MPa). A sketch of the situation can be found in the attachement.

I am not quite sure how to add these stresses and I may overlook something. Any help would be much appreciated. Thank you in advance!