Section 4 Transverse strength

4.1.1 The primary transverse strength members of the dock, throughout its length, are to be capable of withstanding the sum of the following load components:

1. Self-weight of the dock with supporting blocks.

2. Maximum ship weight ordinate obtained from the ship weight curve given in Pt 2, Ch 1, 3.3 Ship weight curve 3.3.1,

   which can be taken as:

   

   Where it is assumed that the entire ship weight is supported throughout its length by keel blocks. Where the spacing between keel blocks is deemed significant, the local loads imposed by the ship may be specially considered, see Pt 2, Ch 1, 5.13 Local strength of the structure in way of keel blocks and supporting structure.

3. External hydrostatic pressure due to given draught. The most severe condition normally occurs when the draught is equal to the depth to the top of the keel blocks.

4. Internal hydrostatic pressure due to the level of evenly distributed ballast associated with the draught as in (c) when lifting at maximum capacity.

5. Wing wall reactions required to give equilibrium on the section under consideration. These reactions at inner and outer wing walls may be taken as equal.

4.1.2 When lifting at maximum capacity with a ship length less than that of the dock, the sections clear of the ship will experience transverse hogging due to the combination of loads in (a), (c), (d) and (e) . Hence, this loading case should also be examined for the sections concerned. The most severe condition will usually occur when the ballast depth is at a minimum (i.e. rest water only).

4.1.3 The compressive and tensile stresses computed for the loading conditions given in Pt 2, Ch 1, 4.1 General 4.1.1 and Pt 2, Ch 1, 4.1 General 4.1.2 should not exceed 170 N/mm². The mean shear stress at any section through the web plating of the primary transverse members should not exceed 95 N/mm² and the Von Mises combined stress at any point should not exceed 180 N/mm².

4.1.4 For the purpose of stress evaluation, the section modulus of the primary transverse strength members is to comprise the continuous transverse material over the effective width of the primary member. The effective width of pontoon deck and pontoon bottom plating is to be taken as per Pt 2, Ch 1, 5.4 Framing or tank stiffeners 5.4.2.

4.1.5 Particular care should be given to the maintenance of transverse strength standard in end sections of floating docks with swim ends where the pontoon depth is reduced.