the ultimatedead load corresponding to the selected pick-up point is then read off from the
appropriate curve. Next the ultimate dead load bending moment is compared with the
ultimate moments of resistance for various sizes of reinforcement as shown on the charts
and the appropriate reinforcement is selected. A partial safety factor of 1.4 on the bending
moment due to dead load is suitable for normal designs, and this value has been used in the
derivation of Figure 7.2 and Table 7.2.
It is evident that there is a maximum lifting length for a pile of given cross-sectional
dimensions and size of main reinforcement. The design curves shown in Figure 7.2 have
been used to obtain the maximum lifting lengths for the three pick-up conditions for square
piles in Table 7.2. Also shown in these tables are the requirements for the link steel over a
length equal to three times the pile width at the head and toe, and in the body of the pile, in
accordance with BS8004.
The reinforcement stress and bar spacing previously referred to ensure that, from
considerations of exposure and durability, a surface crack width of 0.3 mm is not exceeded.
This is permitted by EC2 (Clause 7.3.1) for concrete in foundations in non-aggressive soil,
in wet or rarely dry conditions, and for concrete exposed to sea water including splash zone.
Requirements for cover to reinforcement in aggressive environmental conditions, as
recommended by EC2, are discussed in Chapter 10.
378 Structural design of piles and pile groups
010203040
Length of pile (m)010203040
Length of pile (m)04080120160200240B CArrangement of
reinforcementDesign bending moment,kNm240
200
160120
8040
0280
240
200
160120
80
40
Ultimate r 0esistance moment withDesign bending moment,kNmUltimate resistance moment with04080120160200240280pick up at A300 300 mm 350 350 mm
4 25 mm f4 25 mm f4 32 mm f4 20 mm f4 20 mm f
Pick up at AMain
bars40 mm
cover
to links0.2L0.5L0.5L0.33L 0.6L0.2L
Pick up B Pick up CPick up A0 5 10 15 20 25 51015202530
Length of pile (m) Length of pile (m)0B C B C358060
40
20Design bending moment,^0kNm4 32 mm fUltimate resistance moment withUltimate resistance moment with
Design bending moment,(^80) kNm
60
40
20
(^00)
20
40
60
80
100
0
20
40
60
80
100
(a) (b)
(c) (d)
Pick up at A
400 400 mm
Pick up at A
400 40 mm f
4 32 mm f
4 25 mm f
450 450 mm
4 40 mm f
4 25 mm f
L
Figure 7.2Diagrams showing required lifting points for reinforced concrete piles of various cross-sections
(see also page 337).