Section 8 Double bottom structure
Clasification Society 2024 - Version 9.40
Clasifications Register Rules and Regulations - Rules and Regulations for the Classification of Ships for Service on the Great Lakes and River St. Lawrence, July 2022 - Chapter 4 Ship Structures - Section 8 Double bottom structure

Section 8 Double bottom structure

Parent topic: Chapter 4 Ship Structures

8.1 Definitions

8.1.1 Breadth, B, in the calculations of the double bottom structure, is to be as per Pt 3, Ch 1, 6.1 Principal particulars 6.1.3 of the Rules for Ships and where a hopper side structure has been arranged as per Ch 4, 7.2 Hopper side structure the moulded distance, in metres, may be between the longitudinal bulkheads.

8.2 General

8.2.1 A double bottom structure is generally to be fitted from the collision bulkhead to the after peak bulkhead, and between the side tank longitudinal bulkheads in the cargo hold region, compatible with the design and proper working of the ship.

8.2.2 The requirements of Pt 4, Ch 1, 8 Double bottom structure of the Rules for Ships are to be applied, together with the requirements of this Section.

8.2.3 Longitudinal framing is to be adopted in way of the cargo hold region.

8.2.4 Where the double bottom tanks are interconnected with the wing tank structure, the double bottom scantlings are also to satisfy the requirements of Pt 4, Ch 1, 9 Bulkheads of the Rules for Ships.

8.2.5 The additional requirements for ships specially strengthened for heavy cargoes are given in Pt 4, Ch 7, 1.3 General class notations 1.3.2 of the Rules for Ships.

8.2.6 The buckling requirements of Ch 4, 3.6 Hull buckling strength are to be satisfied.

8.2.7 Special consideration is to be given to double bottom structure for self-unloading bulk carriers.

8.3 Girders

8.3.1 Where a centre girder is to be arranged, a vertical ordinary angle stiffener (or equivalent) may be fitted on one side with a max. spacing 1,00 m, in lieu of a docking bracket.

8.3.2 Side girders, generally two each side of the centreline, are to be fitted in addition to the side tank bulkhead.

8.3.3 Alternative arrangements will be considered on the basis of the results of direct calculations.

8.3.4 Duct keels, where arranged, are to comply with the requirements of Pt 4, Ch 1, 8.3 Girders 8.3.7 of the Rules for Ships.

8.4 Inner bottom plating and stiffening

8.4.1 The minimum thickness of the inner bottom plating on a non self-unloading bulk carrier is to be according to Table 7.8.1 Strengthening for heavy cargo requirements of the Rules for Ships, in association with a maximum stowage rate not exceeding 1,00 m3/tonne. For self-unloading bulk carriers, the minimum thickness is to be as per Pt 4, Ch 1, 8.4 Inner bottom plating and stiffening 8.4.1 of the Rules for Ships.

8.4.2 On self-unloading bulk carriers, the vertical pillars from the cargo hopper support structure clear of the hopper side structure are to be arranged in line with floor and inner bottom longitudinal intersections. Doubling plates shall be arranged on the inner bottom plating under the heels of the vertical pillars. The inner bottom longitudinal slots in the double bottom floors under the vertical pillars are to be closed with collars, where necessary.

8.5 Floors

8.5.1 Where transverse framing is adopted in the wing tanks and longitudinal framing inboard of the longitudinal bulkhead, a transverse bracket is to be arranged in line with the outboard single bottom floor, inboard of the longitudinal bulkhead, extending to the first bottom shell longitudinal inboard of the longitudinal bulkhead, see Figure 4.8.1 Floor.

Figure 4.8.1 Floor
Copyright 2022 Clasifications Register Group Limited, International Maritime Organization, International Labour Organization or Maritime and Coastguard Agency. All rights reserved. Clasifications Register Group Limited, its affiliates and subsidiaries and their respective officers, employees or agents are, individually and collectively, referred to in this clause as 'Clasifications Register'. Clasifications Register assumes no responsibility and shall not be liable to any person for any loss, damage or expense caused by reliance on the information or advice in this document or howsoever provided, unless that person has signed a contract with the relevant Clasifications Register entity for the provision of this information or advice and in that case any responsibility or liability is exclusively on the terms and conditions set out in that contract.