Section 5 Pedestals and foundations

5.1.1 Pedestals and foundations for ship-mounted lifting appliances are classification items. Pedestals and foundations on offshore installations will be considered on the same basis as the main support structure, as required by the coastal state authority or regulatory body.

5.1.2 The loading conditions as defined in Ch 4, 2 Shipboard cranes, Ch 4, 3 Offshore cranes and Ch 4, 4 Submersible handling systems are to be applied in association with the allowable stress levels contained in this Section. Pedestals and foundations for lifting appliances other than shipboard cranes, offshore cranes or submersible handling systems will be specially considered on the basis of this Section, as applicable.

5.1.3 Pedestals, in general, are to be carried through the deck and satisfactorily scarphed into the hull or main support structure. Proposals for other support arrangements will be specially considered. For pedestals not carried through the decks, it is recommended that suitable gussets be provided between the pedestal and the deck to distribute loads to the deck structure.

5.1.4 The pedestal flange in way of the slew ring bearing is to be designed and be of a thickness to provide a rigid and level support for the bearing and bolting. Tolerances and arrangements proposed by the slew ring bearing manufacturer are to be adhered to.

5.1.5 Where it is considered necessary to introduce stiffening brackets to support the flange the spacing of the brackets is to be not greater than that achieved by positioning them between every second bolt.

5.1.6 This Section covers a pedestal structure which is not part of the hull or main support structure of the pedestal. The hull or main support structure is to be designed as per he applicable LR’s Rules for ship types or offshore units. See also Ch 1, 1.1 Application 1.1.13 to determine which parts of pedestals and foundations are covered by which LR requirements.

5.2.1 The pedestal is to be designed with respect to the worst possible combination of loads as detailed in the applicable parts of Ch 4, 2 Shipboard cranes, Ch 4, 3 Offshore cranes and Ch 4, 4 Submersible handling systems. Pedestals and foundations for lifting appliances other than shipboard cranes, offshore cranes or submersible handling systems will be specially considered on the basis of this Section, as applicable.

5.2.2 Stowage arrangements are to be taken into account when calculating the loads applied to the pedestal.

5.3.1 The allowable stress is to be taken as the failure stress of the component concerned multiplied by stress factor, F _p, which depends on the load case concerned. The allowable stress is given by the general expression:

where

5.3.2 The stress factors F _p for steel with ≤ 0,85 are given in Table 4.5.1 Stress factor, F_p .

where

5.3.3 For steel where > 0,85 the allowable stress is to be derived from the following expression:

The stress factor F_p is defined in Table 4.5.1 Stress factor, F_p .

5.3.4 As an alternative to the stress factors F_p as defined in Table 4.5.1 Stress factor, F_p , the stress factors as defined in Table 4.5.2 Alternative stress factor, F_p can be applied, provided all of the following conditions are fulfilled:

1. A fatigue analysis according to a recognised national or international standard (e.g. F.E.M. 1.001) has satisfactorily been carried out taking into account operational loads;

2. Overload protection systems are installed;

3. Beyond a SWL of 160t only engineered lifts are to be carried out;

4. The structural integration of the lifting appliance pedestal into the supporting ship structure is to be verified where required, taking into account the global hull girder stresses for the corresponding loading condition (still water loads and wave loading if applicable) and superimposing the stresses resulting from the lifting appliance operation.

The graphical representation of Table 4.5.2 Alternative stress factor, F_p has been provided in Figure 4.5.1 Stress factor, F_p .

5.3.5 The allowable stresses for welds are to be as per Ch 4, 2 Shipboard cranes.

5.3.6 Steels with > 0,94 are not generally acceptable and will need to be specially considered.

5.3.7 The increase of the allowable stresses due to use of the finite element method is to be as per the principles of Ch 4, 2.17 Allowable stress – Elastic failure 2.17.9.

5.4.1 Lifting appliance pedestals and foundations are to be constructed of steel which complies with LR’s Rules for the Manufacture, Testing and Certification of Materials, July 2022 and the Rules and Regulations for the Classification of Offshore Units, July 2022, as appropriate.

5.4.2 The selected steel grade is to provide adequate assurance against brittle fracture. The steel is to comply with the Charpy V-notch impact test requirements given in Ch 11, 1.2 General material requirements 1.2.2, with the operating temperature chosen as being the lesser of either that from an assigned winterisation notation or the lowest temperature of operation for the derrick system (see Ch 11, 1.2 General material requirements 1.2.4).

5.4.3 The grade of steel for pedestals and foundations on offshore installations or manned submersible handling installations is to comply with the requirements of Ch 4, 3.8 Materials and/or the requirements of the coastal state authority, as applicable.

where

The allowable stress σ_a is to be taken as defined in Ch 4, 5.3 Allowable stresses.

The above formula is intended for initial design calculations of the pedestal flange. In case other effects, e.g. horizontal loading, pre-tension in bolts, size and amount of holes in the flange, reinforcements, plate bending of the pedestal wall t_p, etc. are considered to have a significant influence on the pedestal flange design those effects need to be taken into consideration.

Alternative proposals for the calculation of pedestal flanges will be specially considered.

5.5.2 It is recommended that pedestal flanges be made of forged material. Where rolled plates are applied for pedestal flanges in place of forged material, recognised National or International Standards are to be used to assess the requirement for Z-grade material with the results of the assessment included in the design submission.