The force due to wind acting on a moored drilling unit should be determined using equation here below:

 

 

 

 

​Where

Fw = wind force [N]

Cw = wind coefficient = 0.615 [Ns2/m4]

Cs = shape coefficient

Ch = height coefficient

A = vertical projected area of each surface exposed to the wind, [m2]

Vw = design wind speed [m/s]

 

The projected area exposed to the wind should include all columns, deck members, deck houses, trusses, crane booms, derrick substructure and drilling derrick as well as that portion of the hull above the waterline. In calculating wind areas, the following procedures should be followed:

 

• The projected area of all columns should be included.

• The blocked-in projected area of several deck houses may be used instead of calculating the area of each individual unit. However, when this is done, a sharper factor, Cs of 1.10 should be used.

• Isolated structures such as derricks and cranes should be calculated individually.

• Open truss work commonly used for derrick mast and booms may be approximately by taking 60 percent of the projected lock area of one face.

• Area should be calculated for the appropriate hull draft for the given operating condition.