Section 5 Shell envelope framing

5.1.1 The scantlings of frames, or side longitudinals, web frames or transverses, and stringers below 1,6T above base are to satisfy the requirement of Pt 4, Ch 1 General Cargo Ships and this Section, but may be required to be confirmed by direct calculation. The scantlings of these members above 1,6T from base may require special consideration on the basis of the particular structural arrangements, design deck loading, hull vertical bending stresses, and position of the member above the waterline.

5.1.2 The scantlings of side transverses supporting shell longitudinals above 1,6T are to satisfy the requirements of:

1. Pt 4, Ch 1, 6 Shell envelope framing, Pt 3, Ch 5, 4 Shell envelope framing and Pt 3, Ch 6, 4 Shell envelope framing.

2. The minimum geometric properties required in order to provide rotational constraint to the end of the deck transverse in way:

   

but is not to be less than 0,339S k P _s L _d ² cm³

_s is not to be less than _d cm⁴

5.1.3 The required modulus of transverse main and 'tween deck frames, which may have reasonably constant convex curvature over their entire length, may be corrected for curvature as follows:

5.1.4 Where ramp openings are fitted adjacent to the ship’s side, adequate support for the side framing is to be provided.

5.2.1 The side structure in the forward and after portions of the hull is to be strengthened against bow flare or wave impact pressure. Typically, strengthening is to be considered over the following areas:

• over the after body in way of a flat counter stern which is close to the waterline.
• over the fore end side and bow structure above the waterline and up to the deck at side.
• other areas where the hull exhibits significant flare.

5.2.2 The scantlings of secondary stiffeners are not to be less than:

1. Effective plastic section modulus of stiffeners:

   Z p

   =

   3,75h s s cm kl e 2 x 10–3 cm3

   where

   h s	=	wave impact head, in metres, as defined in Pt 4, Ch 2, 4.3 Strengthening for wave impact loads 4.3.2
   s cm	=	mean spacing of secondary stiffeners, in mm, measured along a chord between parallel adjacent members or equivalent supports, as shown in Figure 2.4.2 Chord spacing and mean chord spacing for secondary members

   Other symbols are as defined in Pt 4, Ch 2, 1.5 Symbols 1.5.2.

2. Web area of secondary stiffeners

   A

   =

   3,7s cm k h s x 10–4 cm2

where

Other symbols are as defined in Pt 4, Ch 2, 1.5 Symbols 1.5.2.

5.2.3 The effective section properties of secondary stiffeners are to be taken as:

1. Plastic section modulus of secondary stiffeners, Z _p, is to be taken as:

1. Web area of secondary stiffeners, A _s, is to be taken as:

5.2.4 Where the stiffener web is not perpendicular to the plating, tripping brackets have to be fitted in order to obtain adequate lateral stability.

5.2.5 The scantlings of primary members are not to be less than:

1. Section modulus of primary members

   Z

   =

   2 γz k h s q v e 2 cm3

2. Web area of primary members

   A

   =

   0,2 γA k h s q v e cm2

   where

   h s	=	wave impact head, in metres, as defined in Pt 4, Ch 2, 4.3 Strengthening for wave impact loads 4.3.2
   	=	and

γ_A and γ_Z are strength factors dependent on the load position

for q < 1 γ_A = q ³ – 2q ² + 2 and γ_Z = 3q ³ – 8q ² + 6q
for q = 1 γ_A = 1 and γ_Z = 1

for web frames:

for primary stringers:

1. The web of the primary member is to be adequately stiffened.

5.2.6 The extents of the wave impact pressure are to be derived as follows:

1. the vertical extent, g _bfv, is to be taken as:

   

2. the horizontal extent, g _bfh, is to be taken as:

   g bfh

   =

   4 m

   where

   =

   K bf and ψ are given in Pt 4, Ch 2, 4.2 Bow flare and wave impact pressures 4.2.1.

5.2.7 For primary members with cut-outs for the passage of secondary stiffeners, and which may have web stiffeners connected to the secondary stiffener, buckling checks are to be carried out to ensure that the primary member web plating and web stiffener will not buckle under the design load. The buckling procedure to be followed is given in Table 5.1.3 Buckling procedure for primary member web plating and web stiffener in Pt 3, Ch 5 Fore End Structure. Where the web stiffener is fitted with a bracket, the buckling capability of the web stiffener in way of the cut-out is to take account of the bracket. Where no web stiffener is fitted, the buckling capability of the primary member web plating is to be checked for the total load transmitted to the connection.

5.2.8 Where the angle between primary structure web and the plating is less than 70°, the effective section modulus and shear area are to take account of the non-perpendicularity.

5.2.9 The structural scantlings required in areas strengthened against bow flare slamming are to be tapered to meet the normal shell envelope requirements.

5.2.10 The side structure scantlings required by this Section must in no case be taken less than those required by the remaining Sections of Pt 4, Ch 2 Ferries, Roll On-Roll Off Ships and Passenger Ships.