Pile Design and Construction Practice, Fifth edition

or parameters derived from in-situ tests. They are shown in Table 4.6. As described below
when Rckis obtained from static pile loading tests the factors are and (Table 4.7) and
when Rckis derived from dynamic impact tests the factors and are used.
The design action Fdin equation 4.2 and the design values of base and shaft resistance
are obtained by dividing the characteristic values of Rbkand Rskobtained from equations 4.3a
and 4.3b by the partial factorsbandsrespectively. These factors are

for actions (A series):Gpermanent andQvariable from Table 4.1;
for ground properties (M series):Mfrom Table 4.2;
for ground resistances (R series):Rfrom Table 4.3 to 4.5; and
correlation factors from Table 4.6.

The above partial factors are selected by adopting one or all of three design approaches
each with a different combination or set of the A, M, and R series. Thus

Design approach 1 (DA1), Combination 1: A1M1R1
Design approach 1 (DA1), Combination 2: A2(M1 or M2)R4
Design approach 2 (DA2), A1M1R2
Design approach 3 (DA3), A1 (or A2)M1R3.

The plus sign in the above list denotes ‘combined with’. As design approach DA1 will be
adopted for pile design by the British National Annex when published. DA2 and DA3 are
not considered in this text.
Taking the case of a pile loaded axially in compression and considering the limit states
STR or GEO, for DA1 Tables 4.2 and 4.3 show that the partial factors for ground properties
and ground resistances are unity. Therefore to ensure that Fdis equal to or not greater than
Rcdthe partial factors are applied to the actions. Accordingly, it is essentialthat the field
operations and laboratory testing techniques should be undertaken in a thorough manner
with the appropriate standard of quality.
Approach DA1, Combination 2 provides for alternative material factors M1 or M2. The
former is used for structural actions while the latter is applied to geotechnical actions caused
by ground movements. Similarly, when approach DA3 is used the action factor A1 refers to

 5  6

 1  2

Resistance of piles to compressive loads 147

Table 4.1Partial factors on actions (F)

Action Symbol Set

A1 A2

Permanent

Unfavourable G 1.35 1.0

Favourable 1.0 1.0

Variable

Unfavourable G 1.5 1.3

Favourable 0 0

Notes

The partial factors shown in Tables 4.1 to 4.8 are those

provided in Annex A of EC7. The mandatory factors to be

applied under the British National Annex are due to be

published in 2008, and should be consulted prior to under-

taking design to EC7 rules.

Different factors will apply to bridges in Table 4.1