Horizontal Stiffness and Damping of Piles in Inhomogeneous Soil

Abstract

A practically-oriented analytical procedure for determining the dynamic stiffness and damping (impedance coefficients) of a laterally-loaded pile in soil exhibiting different types of inhomogeneity with depth, is presented. To this end, an energy method based on the Winkler model of soil reaction in conjunction with pertinent shape functions for the deflected shape of the pile, are employed. A new elastodynamic model for the wave field around a pile is also introduced. The method is self-standing and free of empirical formulae or constants.Dimensionless closed-form solutions are derived for: (1) the distributed (Winkler) springs and dashpots along the pile; (2) the dynamic stiffness and damping coefficients at the pile head; (3) the "active" length beyond which the pile can be treated as infinitely long; (4) the relative contributions to the overall head stiffness and damping of the soil and the pile media.Swaying, rocking and cross swaying-rocking impedances are considered for parabolic, exponential, and multi-layered inhomogeneous soil. The predictions of the model compare favorably with established solutions, while new results are presented. An illustrative example is provided.

Size Limitations for Piles in Seismic Regions

“…(2) and (3) by setting Pp = 0.  being the Winkler stiffness parameter (which is about to 1.5 for inertial loading -see Novak et al, 1978, Roesset, 1980, Dobry et al, 1982, Syngros, 2004, Anoyatis et al, 2016, Karatzia & Mylonakis 2016, qI = 1−(1−2t/d) 4 a dimensionless geometric factor accounting for wall thickness, t, of a hollow pile, Sa a dimensionless spectral amplification parameter, g being the acceleration of gravity.…”

Rotational seismic excitation effects on CIDH pile-supported bridge piers

“…16are not essential assumptions. Alternatives can be found in a recent study by Karatzia and Mylonakis [31].…”

Geotechnical Seismic Isolation Using Eps Geofoam Around Piles

“…(1) refers to perfectly smooth interfaces between pile and inclusion, and between inclusion and soil. k s represents the value of the soil spring constant, typically expressed as k s = δ E s with δ being a dimensionless coefficient typically ranging from 1 to 2.5 depending on soil inhomogeneity, pile-soil stiffness contrast and boundary conditions at the pile head [14][15][16]. A value of 2 was adopted for the herein reported analyses.…”

“…Utilizing the virtual work method and a set of pertinent shape functions for pile deflection [16,17,19,22], the static stiffness coefficients K hh , K rr and K hr corresponding to swaying, rocking and cross-swaying-rocking, respectively, at the pile head can be readily determined. The stiffness terms corresponding to a two-layer soil are [22] …”