Common Structural Rules - Common Structural Rules for Bulk Carriers and Oil Tankers, January 2019 - Part 1 General Hull Requirements - Chapter 3 Structural Design Principles - Section 6 Structural Detail Principles - 8 Double Side Structure
8 Double Side Structure
8.1 General
8.1.1 Side shell and inner hull bulkheads are generally to be longitudinally framed. Where the side shell is longitudinally framed, the inner hull bulkheads are to be longitudinally framed. Alternative framing arrangements are to be specially considered by the Society.
8.1.2 Where the double side space of bulk carriers is void, the structural members bounding this space are to be structurally designed as a water ballast tank. In such a case the corresponding air pipe is considered as extending 0.76 m above the freeboard deck at side. For corrosion addition, the space is to be considered as a void space.
8.2 Structural arrangement
8.2.1 Primary supporting members
Double side web frames are to be fitted in line with web frames in hopper tanks. In addition, double side web frames are to be aligned with web frames or large brackets in topside tanks.
Vertical primary supporting members are to be fitted in way of hatch end beams of bulk carriers or similar large deck opening supporting transverse structure.
In general, horizontal side stringers are to be fitted aft of the collision bulkhead, up to 0.2 L aft of the fore end, in line with fore peak stringers.
8.2.2 Transverse stiffeners
Transverse stiffeners on side shell and inner side, where fitted, are to be continuous or fitted with bracket end connections within the height of the double side. The transverse stiffeners are to be effectively connected to stringers. At their upper and lower ends, shell and inner side transverse stiffeners are to be connected by brackets to supporting stringer plates.
8.2.3 Longitudinal stiffeners
Longitudinal stiffeners on side shell and inner side, where fitted, are to be continuous within the length of the parallel part of the cargo hold region. They are to be fitted with soft toe brackets in way of transverse bulkheads aligned with cargo hold bulkheads and are to be effectively connected to transverse web frames of the double side structure.
Longitudinal framing of the side shell is to extend outside the cargo hold region as far forward as practicable.
8.2.4 Sheer strake
Sheer strakes are to have breadths not less than 0.8 + L/200 m, measured vertically, but need not be greater than 1.8 m.
The sheer strake may be either welded to the stringer plate or rounded.
If the sheer strake is rounded, its radius, in mm, is to be not less than 17 ts, where ts is the net thickness, in mm, of the sheer strake.
The upper edge of the welded sheer strake is to be rounded smooth and free of notches. Fixtures such as bulwarks, eye plates are not to be directly welded on the upper edge of sheer strake, except in fore and aft parts. Drainage openings with a smooth transition in the longitudinal direction may be permitted.
Longitudinal seam welds of rounded sheer strake are to be located outside the bent area at a distance not less than 5 times the maximum net thicknesses of the sheer strake.
The welding of deck fittings to rounded sheer strakes is to be avoided within 0.6 L amidships.
The transition from a rounded sheer strake to an angled sheer strake associated with the arrangement of superstructures is to be designed to avoid any discontinuities.
8.2.5 Plating connection
Connection between the inner hull plating and the inner bottom plating is to be designed such that stress concentration is avoided.
The connections of hopper tanks plating with inner hull and with inner bottom are to be supported by a primary supporting member.
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