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Mariner's Formulae 
Quick reference guide 

Hydrostatic Loading 




HYDROSTATIC PRESSURE
Pressure at any point in a fluid = ρ x g x h [KN/m^{2}]
where ρ = density of liquid [tonnes/metre^{3}]
g = 9.81 [metre/second^{2}]
h = distance of the point from liquid surface [metre]
HYDROSTATIC LOAD
(1) Load acting on an immersed plate = Pressure x Area
= (ρ x g x h) x A [KN]
where ρ = density of liquid [tonnes/metre^{3}]
g = 9.81 [metre/second^{2}]
h = centroid of the immersed area from liquid surface^{*} [metre]
A = immersed area of the plate [metre^{2}]
(2) Load taken by a stiffener of an immersed plate = ρ x g x h x A [KN]
where ρ = density of liquid [tonnes/metre^{3}]
g = 9.81 [metre/second^{2}]
h = centroid of the immersed panel area from liquid surface
= depth of immersion of the plate divided by 2 [metre]
A = immersed area of the rectangular panel plate supported by
the stiffener
= width of panel x depth of immersion [metre^{2}]
CENTRE OF PRESSURE
 the point of an immersed plate at which the resultant hydrostatic load acts.
Centre of pressure from liquid surface
= 2nd moment of area of immersed area about surface
1st moment of immersed area about surface
= I + A(h)^{2} [metre]
A(h)
where I = I _{NA} [metre^{4}]
= 2^{nd} moment of area of the immersed area about
the neutral axis which is parallel to the liquid surface
A = immersed area [metre^{2}]
h = position of the neutral axis from the surface [metre]
= centroid of the immersed area from the liquid surface
CALCULATION OF CENTROID
Centroid of immersed area from liquid surface = Σ (A x y)
ΣA
where Σ(A x y) = Moment of area about liquid surface
= (A_{1}.y_{1} + A_{2}.y_{2} + A_{3}.y_{3} + ....)
y_{n} = distance of centroid of each immersed area, A_{n}
from the liquid surface
ΣA = total immersed area

