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# AWWA D100-05 Wind Pressures

## AWWA D100-05 Wind Pressures

(OP)
Can anyone advise me on the correct interpretation of Kz and how to apply it (Velocity pressure exposure coeffiecient)?  Previously in the D100-96 standard the BCL and the top of tank were the only heights considered for calculating the pressure to use for the entire tank structure.  The wording used to define qz and Kz (D100-05) lead me to believe that Kz should be calculated at the centroid of EACH MEMBER.

Bottom Line:  Should I calculate Kz once using the overall tank elevation and then apply this pressure to the entire tank, Or should I calculate Kz for each individual member?

Any help with this would be much appreciated!
Replies continue below

### RE: AWWA D100-05 Wind Pressures

I believe you CAN calc Kz for each member, but it is often time consuming and not worth the effort.  I would pick the worst case and run with it.

### RE: AWWA D100-05 Wind Pressures

(OP)
Should the worst case be calculated using the overall tank height or the centroid of the tank bowl?  Thanks!

### RE: AWWA D100-05 Wind Pressures

overall tank height.

### RE: AWWA D100-05 Wind Pressures

The way I read the current specification, the pressure for the major parts of the tank (shell plate, for example) are figured for the centroid of that area.  Meaning for a standpipe 150' high, Kz is at 75' or so.  I'm not sure that's the best way to do it, but that's the way it's worded.

If the loads are figured by hand, use uniform pressure.  If doing this by spreadsheet or programming, I'd figure each load at separate height.

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