Chapter 14: Appendices
Appendix 4: Calculating Reaction Forces
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Appendix 4:
Calculating Reaction
Forces
The effect of wind or seismic events on a tank is defined in terms of reaction forces
(downward, upward, and shear). For the sample application used in this appendix, we
will assume that the total horizontal shear equals the equivalent force applied at the
tank’s center of gravity (c.g.). This total shear force will be distributed evenly among the
weigh module supports. Methods for determining wind and seismic forces at a tank’s
center of gravity are discussed in Chapter 4.
CAUTION
THE FOLLOWING CALCULATIONS ARE PROVIDED AS GUIDELINES ONLY. THEY
SHOULD NOT REPLACE A STRUCTURAL ENGINEERING EVALUATION OF THE
APPLICATION BY A REGISTERED PROFESSIONAL ENGINEER WHO IS FAMILIAR WITH
LOCAL BUILDING CODES.
Vertical reaction forces are calculated using statics, which is the study of bodies at rest
(equilibrium). The following factors are used to calculate reaction forces for a tank scale:
h
T
= Height of Tank (feet)
h
L
= Height of Tank’s Legs (feet)
d
= Diameter of Tank (feet)
W
T
= Weight of Empty Tank (pounds)
W
G
= Weight of Full Tank (pounds)
R
1,2
= Reaction Forces at Weigh Module
R
T
= Reaction Force at Weigh Module due to Empty Tank Weight
R
G
= Reaction Force at Weigh Module due to Full Tank Weight
F
= Equivalent Force due to Wind or Seismic Event (applied at tank c.g.)
F
D
= Downward Force on Weigh Module
F
U
= Upward Force on Weigh Module
F
Y
= Vertical Force on Weigh Module
M
A
= Moment about Point A
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