A comparison of initial stiffness formulations for small-strain soil–pile dynamic Winkler modelling. Issue 81 (February 2016)

• Record Type: Journal Article
• Authors: Prendergast, L.J.; Gavin, K.
• Is Part Of: Soil dynamics and earthquake engineering. Issue 81(2016:Feb.)
• Page Start: 27
• Page End: 41
• Publication Date: 2016-02
• Subjects: Piles -- Frequency -- Modulus subgrade reaction -- Dynamics -- SHM; Soil dynamics -- Periodicals; Earthquake engineering -- Periodicals; Sols -- Dynamique -- Périodiques; Génie parasismique -- Périodiques; 624.176205
• DOI: 10.1016/j.soildyn.2015.11.006
• Languages: English
• ISSNs: 0267-7261

Abstract

Abstract: Dynamic Soil-Structure Interaction (DSSI) is an area of much ongoing research and has wide and varied applications from seismic response analysis to offshore wind foundation response. DSSI covers a wide range of load regimes from small-strain vibrations to large-strain cyclic loading. One of the most common ways to model DSSI uses the Winkler model, which considers the soil as a series of mutually independent springs. The difficulty with modelling DSSI arises with the inelastic and nonlinear load–displacement response of soil with increasing strain, therefore modelling of large-strain DSSI relies on the specification of many interrelated parameters. The relative magnitude of these parameters can have a significant effect on the modelled response. In this paper, the specification of an initial stiffness coefficient to model the elastic (small-strain) response of a soil–pile system is investigated. The coefficient of subgrade reaction method can be used to generate spring stiffness moduli for Winkler type models. A number of subgrade reaction theories have been proposed and their application to the problem of static loading has been widely studied. However, relatively little research concerning the application of these models for small-strain dynamic loading has been undertaken. This paper describes a sensitivity study in which a number of subgrade reaction models were used to estimate the frequency response at small-strain levels for a range of pile geometries and ground conditions. A field investigation was undertaken on two piles with different slenderness ratios to estimate the frequency response and damping ratios. The experimental results were compared to predictions of damped natural frequency obtained from numerical models using the force input and measured damping ratio from each experiment. The ability of each subgrade reaction formulation to model the response at small-strain levels is evaluated. Highlights: A parametric study compares subgrade reaction coefficients for Winkler models. A numerical study is performed of the frequency responses predicted by each method. Soil stiffness profiles for loose and dense sand are developed to study density effects. A field test on two piles with different L/D ratios is undertaken for model comparison. The field test stiffness is established from the site G 0 profile.