awwa d100-05 wind pressures

huangyhg

awwa d100-05 wind pressures
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!
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i believe you can calc kz for each   
should the worst case be calculated using the overall tank height or the centroid of the tank bowl?  thanks!
overall tank height.
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.