API-650: EC.9.4.6

[Cobra17]

I'm going through the example problems in API-650 - 2020 edition and for EC.9.4.6, I can't figure out how they go from Xc=23.0 ft to 8,795,200 ft-lb... or Xr for that matter. I get that they are using Ac (convective spectral acceleration parameter), but how does 23ft become 162,874,400?

Xc * Wc = 23.0[ft] * 7,095,000[lb] = 163,185,000... close enough?? or am I missing something

for Xr:

Xr = 41 ft, but I can't figure out where the 100,624,100 is coming from. Xr * Wr is no where close.

 

[JStephen]

It looks like they've mis-labeled things. The line after Xr = is actually the Ai(WiXi+WxXs+WrXr), the first half of the expression inside the square root sign.
The line after Xc is actually Ac(WcXc), the second half of the expression inside the square root sign.
There should have been text that said "Then the first half of this is " or something like that.

 

[Cobra17]

Thanks... I couldn't figure out why they were using Ai and Ac twice.