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Wh resistances are unfactored. The cross that appears against Aa indicates that tolerances are not normally applied to nominal dimensions.

Second, partial factors are applied to ground strengths and variable actions, while non-variable actions and resistances are left unfactored. This is achieved by employing partial factors from Sets A2, M2, and R1 in what is termed 'Combination 2', as illustrated in Figure 6.10. Once again, the crosses on the diagram indicate that the partial factors in Sets A2 and R1 are all 1.0 (except those applied to variable actions) and hence non-variable actions and resistance are unfactored.

(If Design Approach 1 is used to design pile foundations or anchorages, then factors must be applied to resistances instead of material properties. Factors from Set M1 are applied to material properties in both Combinations and factors from Sets R1 and R4 applied to resistances in Combinations 1 and 2 respectively. See Chapters 13 and 14 for a full discussion of this point.)

Numerical values of the partial factors needed in Design Approach 1, for persistent and transient design situations, are:

Design Approach 1 Combination 1 Combination 2

A1 M1 R1 A2 M2 R1

Permanent Unfavourable Yg 1.35 1.0

actions (G)

Favourable YG,fav 1.0 1.0

Variable actions Unfavourable Yq 1.5 1.3

Favourable YQ,fav 0 0

Coeff. of shearing resistance (tan Yep 1.0 1.25

Undrained strength (cu) Ycu 1.0 1.4

Unconfined compressive strength (qu) Yqu 1.0 1.4

Figure 6.11 shows the relative magnitude of the key parameters when using Combination 1 and Figure 6.12 using Combination 2.

In Design Approach 1, partial factors are applied early in the calculation process (to actions and material properties), close to the source of uncertainty. This approach is a particular form of material factor design discussed in Section 6.4.2.

Actions

Verification

Material strength

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