Spring and Dashpot Coefficients for Machine Foundations on Piles

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Title: Spring and Dashpot Coefficients for Machine Foundations on Piles

Author(s): Michael J. O'Rourke and Ricardo Dobry

Publication: Special Publication

Volume: 78

Issue:

Appears on pages(s): 177-198

Keywords: caps (supports) ; concrete piles; damping; foundations; machine bases; soil dynamics; stiffness.

Date: 1/1/1982

Abstract:
This paper presents a simplified procedure for calculating the equivalent stiffness and clamping of a pile supported machine foundation. Separate procedures are developed for the case where there is a small gap between the bottom of the pile cap and the soil surface (Gap Case) as well as the case where there is continuous contact at all times between the bottom of the pile cap and the soil (No Gap Case). The horizontal and vertical spring constants are developed using beam on elastic foundation concepts. Both material and geometric damping contribute to the dashpot coefficients. The radiation or geometric dashpots are developed from wave propagation considerations. The equivalent springs and dashpots for individual piles in the Gap Case compare well with corresponding values obtained from a dynamic finite element program.