Section 3 Side shell structure

3.1 Secondary stiffening

3.1.1 Transverse frames are generally to have scantlings determined as required by Pt 4, Ch 1, 6 Shell envelope framing for cargo spaces, except that where, in a machinery space situated in the midship region, it is desired to omit web frames as permitted by Pt 3, Ch 7, 3.2 Primary structure - Transverse framing 3.2.3, the section modulus of the ordinary main or 'tween deck frames is to be increased by 50 per cent, up to the level of the lowest deck above the load waterline. Where fully effective stringers supported by web frames are fitted, the stringers may be considered as decks for the purpose of calculating the modulus of the frames.

3.1.2 Longitudinal framing is generally to have scantlings determined as required by Pt 4, Ch 1, 6 Shell envelope framing for machinery spaces in the midship region, and by Table 6.4.1 Shell framing (longitudinal) aft Location 2(b) in Chapter 6 for machinery spaces clear of and aft of the midship region.

3.2 Primary structure - Transverse framing

3.2.1 Where the space is situated in the aft end region, web frames are to be fitted, spaced in general not more than five frame spaces apart, extending from the tank top to the upper deck and having scantlings as required by Table 7.3.1 Primary structure in machinery spaces. However, consideration will be given to a spacing of web frames at not more than seven transverse frame spaces apart, in association with substantially increased ordinary frames to satisfy the overall modulus and inertia requirements. The web frames are to be connected at top and bottom to members of adequate stiffness and supported at lower decks by deep beams. If the span of ordinary frames below the lowest deck or flat exceeds 6,5 m, one or more fully effective side stringers are to be fitted to support the frames. These are to have scantlings as required by Table 7.3.1 Primary structure in machinery spaces. Stringers are to be efficiently bracketed to bulkheads, and their connection to the web frames is to be such as to provide adequate continuity of face material.

3.2.2 As an alternative to the fully effective stringers required by Pt 3, Ch 7, 3.2 Primary structure - Transverse framing 3.2.1, an arrangement of light stringers spaced about 2,5 m apart may be accepted. These stringers are to have scantlings not less than those required in the panting region forward, see Pt 3, Ch 5, 4.4 Panting stringers in way of transverse framing.

3.2.3 Where the machinery space is situated in the midship region, it is recommended that web frames be fitted in the engine-room, spaced not more than five frame spaces apart and extending from the tank top to the level of the lowest deck above the load waterline. The scantlings of these webs are to be such that the combined section modulus of the web frame and the main or 'tween deck frames is 50 per cent greater than that required for normal transverse framing. These webs may be omitted if the section modulus of the transverse frames is increased as required by Pt 3, Ch 7, 3.1 Secondary stiffening 3.1.1.

3.2.4 If an effective side stringer supporting the side frames is fitted, then its scantlings and those of the supporting web frames are to be determined from Table 7.3.1 Primary structure in machinery spaces.

3.3 Primary structure - Longitudinal framing

3.3.1 Where the machinery space is longitudinally framed, side transverses are to be fitted having scantlings as required by Table 7.3.1 Primary structure in machinery spaces. For the maximum spacing of transverses, see Pt 3, Ch 7, 1.2 Structural configuration 1.2.4. Transverses are to be connected at top and bottom to members of adequate stiffness and supported at lower decks by transverses or deep beams.