The loading behaviour of initially bent large scale laboratory piles in sand

Field measurements indicate that piles are sometimes bent during driving. This paper reports on the results of an experimental study, at laboratory scale, of the behaviour of bent single piles when subjected to vertical loads. Varying degrees of bend were adopted for both friction and end bearing piles. The test piles, which were embedded in a cohesionless soil, were instrumented to measure the distributions of axial load, bending moment, and transverse shear along the pile shaft.The behaviour of bent piles was found to be far more complex than that of straight piles. For both the friction and end bearing piles, the response of the piles was governed by the degree of bend and the magnitudes of the moments and shears were significant at all levels of the applied load. An important feature in the pile response was the large residual moments and shears locked in the pile on unloading. The implications of the observed pile behaviour in relation to practice are discussed. A review of the reported cases of pile bending is also presented.