7.7 Transversely loaded piles
(1)P The design of piles subjected to transverse loading shall be consistent with the design rules given in 7.4 and 7.5, where applicable. Design rules specifically for foundations involving piles subjected to transverse loading are presented below.
(2)P To demonstrate that a pile will support the design transverse load with adequate safety against failure, the following inequality shall be satisfied for all ultimate limit state load cases and load combinations:
(3) One of the following failure mechanisms should be considered:
- for short piles, rotation or translation as a rigid body;
- for long slender piles, bending failure of the pile, accompanied by local yielding and displacement of the soil near the top of the pile.
(4)P The group effect shall be considered when assessing the resistance of transversely loaded piles.
(5) It should be considered that a transverse load applied to a group of piles may result in a combination of compression, tension and transverse forces in the individual piles.
7.7.2 Transverse load resistance from pile load tests
(1)P Transverse pile load tests shall be carried out in accordance with 7.5.2.
(2) Contrary to the load test procedure described in 7.5, tests on transversely loaded piles need not normally be continued to a state of failure. The magnitude and line of action of the test load should simulate the design loading of the pile.
(3)P An allowance shall be made for the variability of the ground, particularly over the top few metres of the pile, when choosing the number of piles for testing and when deriving the design transverse resistance from load test results.
(4) Records of the installation of the test pile(s) should be checked, and any deviation from the normal construction conditions should be accounted for in the interpretation of the pile load test results. For pile groups, the effects of interaction and head fixity should be accounted for when deriving the transverse resistance from the results of load tests on individual test piles.
7.7.3 Transverse load resistance from ground test results and pile strength parameters
(1)P The transverse resistance of a pile or pile group shall be calculated using a compatible set of structural effects of actions, ground reactions and displacements.
(2)P The analysis of a transversely loaded pile shall include the possibility of structural failure of the pile in the ground, in accordance with 7.8.
(3) The calculation of the transverse resistance of a long slender pile may be carried out using the theory of a beam loaded at the top and supported by a deformable medium characterised by a horizontal modulus of subgrade reaction.
(4)P The degree of freedom of rotation of the piles at the connection with the structure shall be taken into account when assessing the foundation’s transverse resistance.
7.7.4 Transverse displacement
(1)P The assessment of the transverse displacement of a pile foundation shall take into account:
- the stiffness of the ground and its variation with strain level;
- the flexural stiffness of the individual piles;
- the moment fixity of the piles at the connection with the structure;
- the group effect;
- the effect of load reversals or of cyclic loading.
(2) A general analysis of the displacement of a pile foundation should be based on expected degrees of kinematic freedom of movement.