The response of an initially curved cantilever strut with a lumped mass at the tip subject to arbitrary axial impact loads is described, as a model for the dynamic response of unrestrained piles during driving. The differential equation of motion defining the lateral movement of impact-loaded cantilever struts is derived. This equation includes the effect of inertial resistance to motion provided by both the strut self-mass and the mass of the pile hammer. The shape of force pulses produced during pile driving was approximated by an equivalent trapezoidal force pulse. The differential equation of motion was solved for this force pulse using the runge-kutta technique. The solution was found to agree with observed pile behaviour during driving. It is shown that the magnitude of lateral displacements reduces as the mass of the pile hammer increases, because of inertial effects. (Author/TRRL)
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