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Idealized Strip Calculation Explanation

Idealized Strip Calculation Explanation

(OP)
Hello All,
I am working on an analysis of a simple antenna on a pressurized aircraft. This is a XPDR antenna, external doubler, double row of rivets all around, pretty straight forward.

Where I am getting hung up is figuring the end fastener rivet loading. What I am seeing is this could be an example of an "idealized strip" where at fully developed limit load the end fasteners carry the most load, making the corner rivet the critical fastener.

It seems to be tribal knowledge that "the end fastener load is lass than 30% of the total load"

Can any one explain this to me so I can add sufficient explanation in the analysis?
Or is there a better way to explain the corner critical rivet in this explanation?

Thanks all

RE: Idealized Strip Calculation Explanation

Antenna doublers have been discussed many times on this forum. Have you done a search?

The corner rivet is probably not as critical as you might think. First, keep in mind why the doubler is there... to reduce the stress in the skin around the area of a penetration.
These "strip" analyses are based on 2-dimensional analysis through a cross-section of the skin, which only passes through the two planes through the center of the hole. That means that the rivets for which you find the shear transfer load in one plane are far away from the rivets in the other plane. As you follow each row across to the corner, the shear transfer diminishes. Why? Because the rivets near the corners are not in line with the central skin hole any more. All they are doing is sharing load between both skin and doubler, not bridging over a gap in the skin. As you do the strip analysis (Swift, I hope) you aren't looking at the corners. When you complete that part of the analysis, and move on to the bigger picture of the doubler as a whole, that's when you can see the strip analysis applies where the rivet shear transfer loads are the greatest. Everywhere else, the stresses diminish.

That's assuming you have fairly small central hole, a rectangular doubler, that it's made in one piece, not jumping over a skin joint, yadayada and all the other disclaimers.

STF

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