Minimum Thickness Calculation for Riveted Tank Shell

[osers]

Hello all, could anybody explain the API 653 paragraph 4.3.4.1: "E is 1.0 for shell plate 6 in. or more away from rivets. See Table 4.3 for joint efficiencies for locations within 6 in. of rivets.". What does it mean the 6 in. away from rivets?. If possible, please attach a sketch to the answer.

 

[JStephen]

It just means if you're out in the middle of the plate away from the riveted seams, you use a factor of 1.00, otherwise, whatever joint efficiency the table says. It may show there somewhere exactly how that distance is measured. If not, the attached sketch is how I would interpret it.

 

[osers]

Thank you very much JStephen, now I think things are more clear to me, the sketch you attached helped me so much. But I still have a doubt: that mean that for riveted thanks I have to calculate 2 minimum thicknesses, one for the locations within the 6 in. of rivets using E according Table 4.3 and other for locations 6 in. or more away from rivets using E = 1?. Thank you in advance.

 

[fegenbush]

osers,

For tank inspection, you are correct that you must calculate two minimum thickness numbers. This represents two different failure modes: Plate base material yielding (in center of plate) and plate bolt hole rupture (at or near the holes). This is not too dissimilar from the shear lag effect in bolted beam connection design shown in common references such as the AISC Steel Construction Manual.

 

[osers]

fegenbush,

Thank you very much for your answer, now everything is clear.