Section 1 Longitudinal Strength

101. Hull section modulus

1. The hull section modulus at the midship part is not to be less than the values obtained following formulas, whichever is the greater.

Ch 3

from the

Ë Ė Ë Ä Ė

CË G ŊĦŊÈÄËÄ AFÆẄ Ğ ŊĦĒF (cm ), CË G ÈĦÈĖÆ ĜËĦËĒÆË Ä AÆẄFË ĞŊĦŊĖJA FĞ À ZĢ

(cm )

ÄË : Coefficient obtained from the following formula;

Ė

ĖŊŊ

If Ä ≧ 90 m : ËŊĦĒÈ G F JËŊŊ GÄ F JË ,

If Ä < 90 m : ŊĦŊĖ Ä Ğ È

ÆẄ : Block coefficient obtained from dividing moulded volume corresponding to the by LB d

ÄË : Coefficient obtained from the following formula;

load line

ŊĦŊŊËĒ Ä Ğ ŊĦĖÈ

Æ : Coefficient given in Table 3.1

ÀZ : Bending moment(ÝÀ G Ŷ) at still water. see Par 2.

Table 3.1 Coefficient Æ

2. The longitudinal bending moment at still water ÀZ , is to take the greatest value of sagging and hogging moments calculated by a calculation method as deemed appropriate by this Society, in a loaded condition with cargo and ballast or in a working condition at still water.

3. For a dredger of less than 60 meters in length, CË of Par 1 may not be applied. However, in special circumstances, the longitudinal bending moment at still water is to be calculated.

4. A special consideration should be given to shearing stress at the transverse sections with high shearing stress.

102. Calculation of the section modulus of the transverse section of hull One of the followings is to be applied to calculate the hull section modulus.

1. The section modulus on the upper deck is to be calculated by dividing the moment of inertia by

the vertical distance from the horizontal neutral axis to the top of the upper deck beam at ship's side. The section modulus on the ship's bottom, however, is to be obtained from dividing the

above moment of inertia by the vertical distance from the horizontal neutral axis to the top of the

keel.

Ch 3

2. All longitudinal members below the upper deck, regarded to be contributive to the longitudinal strength of hull, is to be included in the calculation. However, for those above the upper deck, on- ly extended part of sheer strake may be included.

3. The openings on the strength deck is to be subtracted from the deck sectional area. However, in case where the small openings (less than 2.5 m in length, and 1.2 m in breadth) are installed, if the sum of the width of those small openings on the same transverse section is not greater than

0.06 (A G ÖẄ), these openings may be neglected in calculation. The of the openings which are greater than 2.5 m in length and 1.2 m transverse sections.

4. The unit of the area is cmË, and the length is m .

ÖẄ is the sum of the widths in breadth on the applicable

103. Loading manual

The master is to be provided with sufficient loading manual approved by this Society to enable him to adjust the cargo loading and ballasting in order to avoid occurrence of the stress not suit- able to the structures of the dredger. However, exception may be made where deemed not neces- sary by this society.