Kinematic Bending of Fixed-Head Piles in Nonhomogeneous Soil

Kinematic bending of elastic single fixed-head piles in continuously inhomogeneous soil is explored in both static and dynamic regime. A generalized parabolic function is employed to describe the variable shear modulus in the inhomogeneous stratum, which can simulate both cohesive and cohesionless soil deposits. The problem is treated numerically by means of rigorous elastodynamic finite-element analyses and simplified beam-on-dynamic-Winkler-foundation (BDWF) formulations. A novel expression is proposed for the active length of a pile in inhomogeneous soil, by means of kinematic interaction considerations. This allows an alternative interpretation of kinematic soil-pile interaction along an effective depth, contrary to existing definitions in which soil response is evaluated at a specific location. Following this interpretation, a design formula for kinematic pile-head moments is derived for both static and dynamic loading. A new dimensionless parameter is identified to govern dynamic pile bending, which allows a straightforward assessment of frequency effects in pile design. (C) 2014 American Society of Civil Engineers.