Section 2 Design requirements

2.1 Codes and Standards

2.1.1 Compliance with the various limit states given in Pt 9, Ch 1, 3 Limit states of design is to be based on analyses for the load combinations given in Pt 9, Ch 2, 3 Load combinations. The resulting concrete section checks are to meet the requirements of a recognised National or International Code or Standard for structural concrete, see Pt 12, Ch 1, 9 Concrete structures, for recognised Codes and Standards.

2.1.2 Not all recognised Codes and Standards adequately address all of the following:

Shell and panel members typical of offshore structures.
Panels subjected to both in-plane and out of plane loads (transverse shear).
Assessment of transverse shear and resistance in directions non-orthogonal to the main axes.
Multi axial stress in concrete.
Crack control and liquid tightness.
The effects of water pressure in cracks and pores on the applied loads and resistance.
Fatigue of concrete, reinforcement and shear steel.
Second order effects including panel buckling.
Discontinuity regions, including complex nodes.

Where the selected Code or Standard does not adequately address all the above areas of design, it should be supplemented by suitable alternatives as agreed by Lloyd’s Register (LR).

2.2 Design loads and design strength of materials

2.2.1 The design loads for a given limit state are obtained by multiplying the characteristic loads defined in Pt 9, Ch 2 Loads and Load Combinations with the appropriate partial load factors given in Table 2.3.1 Load factors and combinations for use with characteristics loads in Pt 9, Ch 2, 3 Load combinations.

2.2.2 The characteristic strength of materials used in design is normally based on the compressive strength of the concrete, the yield or proof stress of the reinforcement or the ultimate strength of a pre-stressing tendon, below which not more than five per cent of all test results are expected to fall. The characteristic fatigue strength is normally based on the value below which not more than 2,5 per cent lie.

2.2.3 For analysis of sections, the design strength of steel for a given limit state is derived from the characteristic strength divided by the appropriate partial safety factor, . The factor () is introduced to take account of differences between actual and laboratory values, local variations, and inaccuracies in assessment of the resistance of sections. It also takes account of the importance of the limit state being considered.

2.2.4 For analysis of sections, the design strength of concrete for a given limit state is derived from the in situ strength divided by the appropriate partial safety factor, . The in situ strength of the concrete is a function of the characteristic strength and is defined in the selected concrete structural Code or Standard.

2.2.5 It is vital that the material factor, , used in the design is consistent with the requirements of the selected concrete structural Code or Standard, for all materials and limit states.