Section 3 Design Loads

301. Loads

1. The modes of operation for each unit are to be investigated using realistic loading conditions in- cluding gravity loading with relevant environmental loading for its intended areas of operation. The following environmental considerations should be included where applicable: wind, wave, current, ice, seabed conditions, temperature, fouling and earthquake.

2. Drawings of a unit are to be approved for the environmental conditions. Where possible, the above design environmental conditions apply to units and structural members should be based upon sig- nificant data with a period of recurrence of at least 50 years for the most severe anticipated environment.

3. Results from relevant model tests may be used to substantiate or amplify calculations.

4. Limiting design data for each mode of operation should be stated in the operating manual.

302. Wind loads

Sustained and gust wind velocities, as relevant, should be considered when determining wind loading. Pressures and resultant forces should be calculated by the method referred to in section 4.2 or by some other method to the satisfaction of the Society.

303. Wave loads

1. Design wave criteria should be described by design wave energy spectra or deterministic design waves having appropriate shape and size. The design wave height to be used for wave load calcu- lation may be specified by the Owner under the approval of the Society. The design wave period to be used for wave load calculation is to be the period which gives the maximum effect to the unit.

2. The wave forces utilized in the design analysis should include the effects of immersion, heeling and accelerations due to motion.

3. In calculating wind loads, the following requirements are to be applied.

(1) The wave loads are to be calculated, based on acceptable wave theories appropriate to the de- sign depth of water at the operation area subject to the approval by the Society. The wave loads, however, may be determined from the tank test approved by the Society on a model of the unit.

(2) Waves from all directions are to be considered on the unit.

(3) The wave loads produced by shipping water on the deck, the loads acting directly on the im- mersed elements of the unit and the loads resulting from heeled positions or accelerations due to its motion are also to be considered.

(4) The vibration induced by waves is also to be considered.

304. Current loads

Consideration should be given to the interaction of current and waves. Where necessary, the two should be superimposed by adding the current velocity vectorially to the wave particle velocity. The resultant velocity should be used in calculating the structural loading due to current and waves.

305. Loads due to vortex shedding

Consideration should be given to loading induced in structural members due to vortex shedding.

306. Deck loads

For deck loads, uniform and concentrated loads on the respective portions of the deck in each

mode of operation and transit condition are to be taken into account. The values of the loads, however, are not to be less than given in Table 3.1.

uniform

Table 3.1 Deck Loads

307. Other loads

Other relevant loads should be determined in a manner to the satisfaction of the Society.