Iranian Classification Society Rules

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Section 6 Stiffeners

601. Section modulus

1. The section modulus of stiffeners is not to be less than that obtained from the following formula :

: bending moment factor, defined in Table 3.4.9 and Table 3.4.12, for load and boundary

conditions and for, not defined in previous Tables, tic bending theory.

: span of the stiffeners (m ).

spacing of stiffeners (m ).

-values are directly from general elas-

: designed pressure, defined in Ch 2.

allowable stress, defined in Table 3.4.5.

Table 3.4.9 Bending Moment Factor ( )

Structures
Continuous longitudinal members	85
Non-continuous longitudinal members	100
Transverse members	100
Vertical members, and fixed	100
Vertical members, simply supported	135
Bottom longitudinal members	85
Bottom Transverse members	100
Side longitudinal members	85
Side vertical members	100
Deck longitudinal members	85
Deck Transverse members	100
W.T. bulkhead stiffeners, fixed ends	65
W.T. bulkhead stiffeners, fixed on ends (lower)	85
W.T. bulkhead stiffeners, simply supported ends	125
W.T. bulkhead horizontal stiffeners, fixed ends	85
W.T. Bulkhead horizontal stiffeners, simply supported	125
W.T. bulkhead stiffeners, fixed one ends (upper)	75
Tank cargo bulkhead, fixed ends	100
Tank cargo bulkhead, simply supported	135
Deckhouse stiffeners	100
Casing stiffeners	100

2. The values, defined in Par 1, are to be regarded as the requirement about an axis parallel to the plating. As an approximation the requirement to standard section modulus for stiffeners at an obli- que angle with the plating may be obtained if the formula in Par 1 is multiplied by the following factor.

: angle between the stiffener web plane and the plane perpendicular to the plating. However, for -values less than 12° corrections are normally not necessary.

3. When several members are equal, the section modulus requirement may be taken as the average re- quirement for each individual member in the group. However, the requirement for the group is not to be taken less than 90 % of the largest individual requirement.

4. Front stiffeners of superstructures and deckhouses are to be connected to deck at both ends with a connection area not less than that obtained from the following formula :

And, side and after end stiffeners in the lowest tier of erections are to have end connections.

5. The section modulus of longitudinals or transverse stiffeners supporting the bottom plating is not to be less than that obtained from the following formula :

bending moment factor.

= 85, conventional longitudinals.

= 100, transverse stiffeners.

slamming pressure, defined in Ch 2, 301.

: allowable stress, 180/

6. The shear area of longitudinals or transverse stiffeners less than that obtained from the following formula :

supporting the bottom plating is not to be

allowable stress,

: spacing of stiffeners (m

as defined in Par 5.

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