I recently performed the design of a rectangular steel tank using Solidworks FEA. The was setup as per the tutorials within this forum, using a non-uniform distributed pressure of 9810 n/m^2 along the side walls, as per the attached. The FEA result showed a deflection of 8mm maximum from this simulation setup which was acceptable. The tank was this built according to this design, however, much to my dismay the deflection on the side walls was vastly greater than 8mm, it was in fact in the region of 35mm and I believe close to failure! The tank is bulging out at the bottom of the tank roughly a 1/4 of the way up, a result which is barely present on the simulation.

Either I did not set the simulation up correctly or Solidworks FEA is not reliable. I would greatly appreciate it if some light could be shed on the situation?

My tank model and simulation is attached. I have also included a photo of the actual tank, if you zoom in you can see it bulging on the opposite end.

Any help would be greatly appreciated.

Regards