Vertical Shell Stiffening Guidance

[theonlynamenottaken]

I'm working on an aging tank with significant loss of shell thickness. There is slated to be shell replacement in the future, if not total tank replacement. In the meantime, there is a need to increase the vertical buckling capacity of the shell as a whole.

I've been given the task of designing vertical stiffeners for the tank. I haven't been able to find much guidance on this, only really finding guidance on horizontal/ring stiffening.

Does anyone know of good references or applicable sections of codes & standards? Am I headed in the wrong direction overall with this notion of vertical stiffeners? Designing the stiffeners to carry the loads alone is overly conservative - I need to be able to include a portion of the shell to act with the stiffeners...

 

[JStephen]

In new construction, it is more cost-effective to increase plate thickness than to add vertical stiffeners, so you don't normally see them used.

In terms of analysis, you might look at two options. The AISC codes include provisions for stiffened plates with width exceeding the non-compact limits, and those provisions could reasonably be used. Then also, the latest AWWA D100 includes flat plates stiffened on each side, intended for fluted-pedestal elevated tanks.

There are also provisions in the codes for the increased stability of a cyclinder due to internal pressure.

You could also have a situation where you can show by calculation that the tank is reasonably adequate, but it doesn't meet API-653, either.