OCIMF_Mooring_Equipment_Guidelines_(Second_Edition)

reaction applies a moment about the cent reline, which must be resisted by the interlocking chain
link. The manner in which this resisting moment is applied is complicated. For the purpo e of
analysis, a resisting moment N between chain Links will be assumed to act about t.he chain link
centreline.

The venica1 component of the interlink tension is P sin al2. This force applies a bending moment
M at the centre of the chain link. From the dimensions of the link, this moment is

M - 2dP sin a/2

Considering the chain link as a beam consisting of two cylinders, each with its cenlreline a distance

u from t.he celltroid, the moment of inertia is

7rrl4 rodl( 1.3d sin fJ)'

+ -------------

32 2

The maximum tensile stress in Ihe chain is at the top cen!Te of the link. The distance to the outer

fibre at that point is

c = x = 1.3d sill {J + O.5d

By superposition of the tensile force which is exened by tbe horizontal component of P acting on
the area of the li.nk and the ma'(jmum tensile force whjch is produced by lhe vertical component of
P applying a moment M, the total stress at this point is

2P cos al2 2PdC sin al2

To facilitate plolting and comparison of the stress level, a non-dimcllsionaJ stress parameter is

defined by multjplying lhe abo~'c equation by d llP

(Id" 2 2edJ

• cos a/2 + --sin al2
  P 7r I

This factor has been plotted in Figure F6 as a functjon of the diameter ratio for various angles (3.

For cODvenience the surface diamet.cr corresponding to 76 mm (3 in.) chain is also indicated on

the abscissa of tne figure.

F.4 INCREASE IN MAXIMUM STRESS

Marsh and ThUIston analyzed the stress distribution in a stud Link cbain under straight tension

using Stress equations which are more sophisticated than those used here. They measured these

stresses by strain gauging chain links. The results of their analysis (figure 3 of Marsh and Thurston

reference) sbow the maximum tension stress in straight tension occurs at the outside of tJ1C link

at a position about 70° from tbe end of the link. The non-dimensional value of this stres s,

adl

is 2.

P

This non-dimensional stress value is plolled as a horizontal dashed line in Figure F6. It ind.icates

that the maximum stress due to straight tension is higher than that due to being lensioned over

the surface for snrface to chain diameter ratios greater than about 7 when {J = 250 • The actual

diameter ratio al which stress due to tensioning over the surface becomes greater than thai due

(0 tensiorurrg over the surface becomes greater than that due to straight tension depends on the

angle {3, which is undetermined.