Analysis Method for Laterally Loaded Pile Groups Using an Advanced Modeling of Reinforced Concrete Sections

Abstract

A Boundary Element Method (BEM) approach was developed for the analysis of pile groups. The proposed method includes: the non-linear behavior of the soil by a hyperbolic modulus reduction curve; the non-linear response of reinforced concrete pile sections, also taking into account the influence of tension stiffening; the influence of suction by increasing the stiffness of shallow portions of soil and modeled using the Modified Kovacs model; pile group shadowing effect, modeled using an approach similar to that proposed in the Strain Wedge Model for pile groups analyses. The proposed BEM method saves computational effort compared to more sophisticated codes such as VERSAT-P3D, PLAXIS 3D and FLAC-3D, and provides reliable results using input data from a standard site investigation. The reliability of this method was verified by comparing results from data from full scale and centrifuge tests on single piles and pile groups. A comparison is presented between measured and computed data on a laterally loaded fixed-head pile group composed by reinforced concrete bored piles. The results of the proposed method are shown to be in good agreement with those obtained in situ.

Analysis of Laterally Loaded Piled Raft Foundation

“…For reinforced concrete sections the 'moment-curvature-axial load' relationship is obtained taking also into account the influence of tension stiffening (Morelli et al, 2017 [30]). The pile flexibility matrix is thus updated according to the bending-moment reached at each pile-node in the previous step of the analysis procedure [26].…”

“…Where: Gtan, Gsec (Equation 3) and Gmax are the tangent, the secant and the maximum shear modulus of the soil, respectively; Rf and g are the parameters that define the shape of the modulus reduction curve in the formulation proposed in [31]. As fully described in [26,33] an analogy is assumed between the "interface pressureultimate soil resistance" ratio and the "shear stress -maximum shear stress" ratio (p/pult  /max). The ultimate lateral soil pressure profile is evaluated according to the relationships suggested in the API recommendations [16].…”

“…The shadowing effect [34] and the influence of suction (in case of partially saturated soil layers) are modelled using an approach similar to that described in Ashour et al (2004) [34] and the Modified-Kovacs model (Aubertin et al, 2003 [35]), respectively. Details are shown in [26,33].…”

“…Both free-to-rotate and fixed-head piles can be studied, nevertheless a different pile-head restraint condition can be considered. The analyses are performed incrementally as described in [26,33].…”

Pile-Head Kinematic Bending of Fixed-Head Long Piles in Homogeneous and Layered Soils Considering Pile and Soil Material Nonlinearities in Case of Moderate to Strong Earthquake Motions

“…KIN SP and ONDA are completely merged to provide a stand-alone analysis tool. Detailed description of the main assumptions in KIN SP are presented in [19,24,25]. In [18] KIN SP has been enhanced to consider the reinforced concrete model proposed by Andreotti and Lai (2017) [26].…”