OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

Although dynamic erfects are not explicitly included i.n the above criteria, the design margin>~ are
considered cOllservative and may alJow for some dynamics. At terminals where dynamic effects from
pass"ing ships, wave actioD, etc. are significant, shore-based mooring equipment may have to be
deployed to supplement the ship's equipment.

2.3 COMPUTATION OF ENVIRONMENTAL LOADS

FOR ANY WIND AND CURRENT COMBINATION

Environmental loads induced by wind and curre nt can be computed with the procedures described

in Reference 3 which are al.so listed in this ee tion for ease of reference. The forces and moments

generated are suitable for a computer analy. is of the required mooring restraint. Tbe foHowing

non-dimensional coefficients are used in tbe calculation of design loads:

C. - longitudin al force coefficient

C, - lateral force coefficient

C" - yaw momenl coefficient

Additional subscripts wand c are used to distinguish between wind and current.

The sign convention. and coordinate system adopted are illustrated in Fig. 2. I. Force and moment

coefficients are a function of wind and current angle of attack. The wind and current coefficient

are based upon data obta ined from model tests.

Instead of a latera.l force coefficieot and a ~'aw moment coefficiem, some sources quote a late ral

force coefficient at the forward perpendicuJar (CYF) and a lateral force coefficient at the aft per-

pendicular (CyA). T his is generally more convenient for hand calculations , but either convention ca n

be converted to lhc other with the following equations:

(a) From total force/yaw moment system to forces at perpendicular syStem:

eYA = t c , -C,y

(b) From forces at perpendicular system to total force/yaw moment system:

The wind forces/momenl acting on a moored ship are calculated using the following equations:

Longitudinal F"" ==. c,~ ( 7600 p", ) , V;,AT (I)

wind force

Lateral wind F yw c"..,( ~) V~.Al (2)

force^7600

Wind yaw moment M.., .... = C w ( ~ ) Vl Al Lsp

7600 -

(3)

The current forces/moment acting on a moored ship are calculated using the equations:

Longi t udinal

current force

(4)