ASME PTB-4, E.4.12.2 Reinforced Vessel of Rectangular Section: there is an inconsistency in data

[Josep Maria Perdigo]

In ASME PTB-4, example E.4.12.2 - Reinforced vessel of Rectangular Cross Section, there is an inconsistency in the stiffener data: The moment of inertia is not consistent with the height and area of the rectangular section. Let's see:
- Stiffener shape: rectangular
- Stiffener cross sectional area: Astif = 3.83 in^2
- Stiffener moment of inertia: Istif = 11.3 in^4
- Stiffener height: hstif = 4.125 in
- With the height and the area, we calculate the thickness: tstif=3.83/4.125 = 0.928485 in
- The moment of inertia of the rectangular section is calculated as follows:
Istif.calc = (1/12)*tstif*hstif^3 = (1/12) * 0.928485 * 4.125^3 = 5.4308 in^4 ,
which as you can see, is less than the ASME data: Istif = 11.3 in^4
- In the calculation of I11 (PBT-4, page 248), if we substitute Istif = 11.3 for the value we have calculated Istif.calc = 5.4308 in^4, we obtain:
I11 = 17.0389 in^4 instead of I11 = 22.9081
- If we measure the moment of inertia of the composite section of PTB-4, figure E4.12.2, with a CAD program, we obtain: I11 = 17.0389 in^4

I would be grateful to know if anyone has encountered this inconsistency, or is kind enough to check and confirm or revoke it.
Thank you

 

[pdiculous963]

You are correct, there is an inconsistency here. The stiffening member used in the calculations was a W4x13, however, it was drawn incorrectly in the book.