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# Load Summation messed up with Seismic Loads

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## Load Summation messed up with Seismic Loads

(OP)
I have been running several iterations of the same 10 story building throughout the life of this project.  We have high windspeeds and (very) low earthquake forces.  Until today, I have not considered the effects of earthquakes.

I have gone through a half dozen iterations of the model and seen that the summation of reactions from DL, LL, SIDL, WindX, and WindY are generally the same, i.e:
Dead = 27,174 k (FZ)
Live = 19,828 k (FZ)
SIDL = 12,650 k (FZ)
WindEast = -757 k (FX)
WindNorth = -1,320 k (FY)    5 k (FX)
All other reactions not listed above are 0.00.

Then I add Earthquake as a primary load cases in the X and Y, and my summation of reactions is:  (FX, FY, FZ)

Dead  -1,060,  30,  27,088
Live  -563,  5,  19,828
SIDL  -169,  -65,  12,832
WindEast  -95,  26,  0
WindNorth  256,  3,678,  0
QuakeEast  -141,  -48,  0
QuakeNorth  167,  2,412,  0

As you can see, the north wind reaction goes from -1320k to 3678k, in the other direction!!!

All I have to say is What the Eff, yo!

I dont care how poorly I inputed the quake loads, my wind forces shouldn't change!

Anyone had this problem or know how I messed my model up?

Regards,

Noma

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