Abstract: Dynamic stiffness for lateral vibration of a viscoelastic floating pile in a nonlinear viscoelastic soil layer is investigated. We make the soil portion below the floating pile end equivalent to a virtual soil-pile and divide the whole soil layer into a nonlinear viscoelastic inner zone and a linear viscoelastic outer zone. This way, a semi-analytical solution for dynamic behavior in the frequency domain of the composed pile is obtained using the equivalent linearization method and variable separation method. Expressions of dynamic stiffness on top of the floating pile are given. Dynamic stiffness of the pile are then analyzed numerically for different vibration frequencies. Effects of the physical and geometrical parameters are examined. It is revealed that the dynamic lateral stiffness of the floating pile depends heavily on the amplitude of the vibration, nonlinear soil property, pile length, etc. Generally, stiffnesses of the pile are significantly decreased due to soil nonlinearity. Furthermore, the increment of stiffness cannot be achieved only by increasing length of the floating pile. There exists an optimization pile length. The results obtained are useful in pile design.

Key words: lateral vibration, nonlinear dynamic stiffness, pile-soil interaction, floating pile