Section 6 Shell envelope framing

6.1.1 The requirements of this Section, unless specified otherwise, are applicable to all ship types, NS1, NS2 and NS3.

6.1.2 The requirements in this Section apply to longitudinally and transversely framed shell envelopes. The basic structural scantlings of NS1 ships are to be determined in accordance with Vol 1, Pt 6, Ch 3, 3 NS1 scantling determination. The basic structural scantlings of NS2 and NS3 ships are to be determined in accordance with Vol 1, Pt 6, Ch 3, 4 NS2 and NS3 scantling determination. The arrangement of framing is to be in accordance with Vol 1, Pt 3, Ch 2, 3.4 Shell framing

6.1.3 The geometric properties of stiffener sections are to be in accordance with Vol 1, Pt 6, Ch 2, 2.9 Proportions of stiffener sections

6.1.4 Higher tensile steel longitudinals within 10 per cent of the ship’s depth at the bottom and deck are to be continuous irrespective of the ship length, see also Vol 1, Pt 6, Ch 6, 6.5 Arrangement at intersection of continuous secondary and primary members

6.1.5 Stiffeners and brackets on side transverses which are connected to higher tensile steel longitudinals are to have their heels well radiused to reduce stress concentrations. Alternative arrangements will be considered if supported by appropriate direct calculations, see also Vol 1, Pt 6, Ch 6, 6.5 Arrangement at intersection of continuous secondary and primary members

6.1.6 Where higher tensile steel side longitudinals pass through transverse bulkheads in the 0,4L _R amidships, well radiused brackets of the same material are to be fitted on both the fore and aft side of the connection. Particular attention should be given to ensuring the alignment of these brackets. Alternative arrangements will be considered if supported by appropriate direct calculations.

6.1.7 Where higher tensile steel asymmetrical sections are adopted in double bottom tanks which are interconnected with double skin side tanks, the requirements of Vol 1, Pt 6, Ch 3, 6.1 General 6.1.5 and Vol 1, Pt 6, Ch 3, 6.1 General 6.1.6 are to be complied with regarding arrangements to reduce stress concentrations. Alternatively, it is recommended that bulb plate or symmetrical sections are adopted.

6.1.8 Where appropriate all ship types are to comply with the requirements of Vol 1, Pt 6, Ch 3, 14 Strengthening for bottom slamming for bottom slamming and Vol 1, Pt 6, Ch 3, 15 Strengthening for wave impact loads above waterline for wave impact above the waterline.

6.2.1 Where struts are fitted to side shell transverse web frames or longitudinal stringers to carry axial loads, the strut cross-sectional area is to be derived as for pillars in Vol 1, Pt 6, Ch 3, 12 Pillars and pillar bulkheads. If the strut is fitted at the primary member half span point, the primary member section modulus may be taken as half the modulus derived above.

6.2.2 Design of end connections is to be such that the area of the welding is to be not less than the minimum required cross-sectional area of the strut. To achieve this, full penetration welding may be required. The weld connections between the face flats and webs of the supporting structure are to be welded using double continuous welding of an equivalent area.