Question interpretation of "r" value in AWWA code

[chrislaope]

I would like to get an answer from those who used AWWA code (Factory-Coated Bolted Carbon Steel Tanks for Water Storage) before.

in page 15 of this code, it says:

r = force transmitted by bolt or bolts at the section considered, divided by the tensile force in the member at that section.

My question see attached pdf file.

Thanks.

 

[chrislaope]

AWWA code page 15 is attached here.

 

[jec67]

I see the key phrase "..at the the section...". Since you only have one bolt at the section (perpendicular to the direction of force), then it depends on which bolt you are looking at. The bolt closest to the end has a force of 0.5F, but the member only has 0.5 F in it at that point (the other 0.5F is transferred into the member at the inner bolt), so r=1.0 at that location. The inner bolt will have r=0.5.

 

[chrislaope]

@jec67 (Structural):
thank you for sharing your opinion, but it does not answer my question.

Here is the situation, on my desk, there are 2 design proposals from 2 different engineering company for a same size of water tank project.

One company interpret "r" value in AWWA Code as the fraction of the force in one bolt out of that section, therefore r=0.5, which results in a lighter design.

the other company interpret "r" value in AWWA Code as the force in the bolts (in this case 2 bolts) divided by the force in that section, therefore r=1.0, which results in a heavier design.

the original paragraph in AWWA code is as follows:

r = force transmitted by bolt or bolts at the section considered, divided by the tensile force in the member at that section.

what I would like to know is which interpretation for the "r" value in AWWA code is correct. Has anybody in this forum ever designed bolted water tank before? and how did you handle "r" value when you design bolted water tank?

Thanks.

 

[jec67]

chrislaope

I interpret the AWWA the same as the company that uses r=1.0. The bolt closest to the end of the plate has a force of 0.5T but the plate has a force of 1.0T; therefore, the r value is 1.0. It is a question of bolt force vs. plate force at the section considered.