Pile Design and Construction Practice, Fifth edition

where m is the modular ratio of steel to grout (take conservatively as 18 in absence of other data
for long term, i.e. 28 days or more), D is the outside diameter, t is the wall thickness. The
suffixes g, p, and s refer to the grout, pile and sleeve respectively.
The basis of equation 6.6 was a research programme described in references 6.4 (a) to (c).
This covered a limited range of geometry of the pile connections. For this reason the
Department of Energy have applied limits to the values of C L as follows:
L/D p
C L
2 1.0
4 0.9
8 0.8
�12 0.7
Where L is the nominal grouted connection length, referred to in EC7 (Section 8) as the
tendon bond length. Obtain intermediate values for L/D p�12 by linear interpolation.
The surface condition factor C s should be taken according to the following:
(i) If shear connectors are present and satisfy requirement h/s�0.005 take C s as 1.0.
(ii) For plain pipe connections and for connections with shear connectors but with
h/s�0.005, in the absence of test data take C s � 0.6.
The values in (i) and (ii) refer to shotblasted or lightly rusted surface conditions. Other
conditions (e.g. painted surfaces) should receive special consideration.
Equation 6.6 should be applied only to connections which satisfy the geometrical limits
given below, and where mechanical shear connectors are used they are present both on pile and
sleeve surfaces in contact with grout; the connectors are at uniform spacing along the length
of the connection; outstand and spacing of shear connectors on pile and sleeve are the same;
shear connectors on driven piles should cover sufficient length to ensure contact with grout
after driving; shear connector cross-section and welds on each grout/steel interface should be
designed to transmit total load applied to the grouted connection. The geometrical limits are
Sleeve geometry 50 � (D/t)s � 140 Pile geometry 24 � (D/t)p � 40
Grout annulus geometry 10� (D/t)g � 45 L/D p �2
Shear connector height ratio 0 * �h/D p �0.006
Shear connector spacing ratio 0 * �D p /s�8
Shear connector ratio 0 * �h/s�0.04
Shear connector shape factor 1.5�w/h�3 (consistent with welded square bar or
hemispherical weldbeads)
where w is the nominal width of the shear connector including welds.
The American Petroleum Institute recommendations (3.5) are much simpler. The equations are:
For operating and environmental conditions combined with dead loads and maximum or
minimum live loads appropriate to normal operations of the platform:
f ba � 0.138 � 0.5f cu h s (MN/m2 )
Piles to resist uplift and lateral loading 319
(6.8)