Dynamic pile impedances for fixed-tip piles

The behavior of a laterally loaded pile with fixed-tip boundary condition (i.e., displacement and rotation, are perfectly restrained) is evaluated using a recently proposed, improved Tajimi-type model. The model performance in both, static and dynamic regime is first validated against rigorous finite element solutions and subsequently compared with Winkler model results for a selected range of pile-soil system parameters. In addition, pile impedances for fixed-tip piles are compared with previously proposed impedance expressions for hinged-tip piles. Results indicate that pile tip fixity has moderate impact on the pile stiffness in rotation but show stronger influence for pile stiffness in swaying and cross-swaying. The effect of tip fixity on pile impedances diminishes when piles are longer than approximately ten pile diameters. The proposed expressions for damping were evaluated across a wide range of frequencies, and damping was found to be most pronounced in rotation across the entire spectrum of pile-soil stiffness ratios examined. Winkler based formulations from literature almost exclusively over-predict damping for fixed tip piles.