Offshore Structure Loads and Strength - Offshore Structures: Design, Construction and Maintenance - page 55

load, the angle of inclination of the wind direction to the platform should be
considered in each direction.

Example
Pipe Dia. = 0.4 m

V air = 25m ⁄ s V water = 1m ⁄ s

1m 2 1m 2

a air = ⁄ s a water = ⁄ s

m 3 m 3 ρ air = 1 : 3kg ⁄ ρ water = 1000 kg ⁄

V 2

F d = ð1 = 2Þ × Cd × ρ × × A

× ρ × π × ð D 2 F m = Cm / 4Þ × a

Air

2

F d = ð1 = 2Þð0 : 8Þð1 : 3Þð25Þ ð0 : 4Þ = 130N

2

F m = 2ð1 : 3ÞðπÞð0 : 4Þ = 4 ð1Þ = 0 : 33N

Water

2

F d = ð1 = 2Þð0 : 8Þð1000Þð1Þ ð0 : 4Þ = 160N

2

F m = 2ð1000ÞðπÞð0 : 4Þ = 4 ð1Þ = 251N

Conductor Shielding Factor
Depending on the configuration of the structure, the number of well conduc-
tors can add a significant portion to the total wave forces. If the conductors
are closely spaced, the forces on them may be reduced by hydrodynamic
shielding.
However, there will be no reduction factor due to shielding when the
spacing between conductors is equal to or greater than 4 times the conductor
diameter. With closer spacing, the following equation can be applied:

S f = 0 : 25 ð S = D c Þ

where S f is the shielding reduction factor, S is the spacing between conductors,
and D c is the conductor diameter.

2.5.2 Current Force
According to ISO 9002, the most common categories of ocean currents are:

Wind-generated currents

●

Tidal currents

●

Circulational currents ●

Loop and eddy currents ●