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Support Beam in Skirt Anchor Box

MchA

Mechanical
Joined
Dec 5, 2023
Messages
24
Location
IT
Hello everyone,

I’d like to clarify a doubt regarding the skirts used for reactor and column towers.

In many cases, I’ve seen a support beam (e.g., an IPE profile) installed inside the skirt, typically located midway or near the base within the anchor box area, as shown in the picture below. However, design codes such as ASME VIII Div. 1/2 and EN 13445-3 generally focus only on the skirt and anchor box calculations — and don’t provide specific guidance or requirements for adding a reinforcement beam inside the skirt.

I’m trying to understand how the necessity of such a support/stiffening beam can be justified:
  • Is it usually based on FEA or specific local stress concerns?
  • Could it be considered overly conservative or unnecessary in standard designs?
  • Are there any recognized guidelines or analytical methods to define when it is needed?
  • From your experience, is there any cost/benefit evaluation or design philosophy that helps decide whether to include it or not?
In my case, I have a column with a fabricated weight of 125 tons, about 200 tons including internals. The skirt has been designed to withstand this weight along with wind and earthquake loads.

We were considering installing an IPE300 beam inside the skirt, partly to help during lifting operations. However, it has been pointed out that this beam could negatively affect the structure, since the top and bottom rings (as well as the entire anchor ring) may not work properly — the skirt could ovalize, and the entire load might transfer to the welds between the skirt and the beam.

I plan to evaluate this by FEA, but I would also really appreciate your opinions, experiences, or any reference literature regarding this design detail. Is there any analytical method or empirical justification to support (or avoid) this approach?

Thank you in advance!
 

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What you're looking at are base ring stiffeners. They really only help with lifting, they increase stiffness to help distribute load from the tailing lug throughout the skirt/base ring.

Take a look at Dennis Moss' Pressure Vessel Design Manual. I have the 3rd edition, and section 7-5 gives a method of design. COMPRESS software also can calculate stresses in the base ring with stiffeners.

Here's another post talking about them: https://www.eng-tips.com/threads/stiffener-beam-tailing-lugs.179407/
 

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