https://accedacris.ulpgc.es/jspui/bitstream/10553/16238/3/Padron_Dynamic_Structure.pdf

Dynamic structure soil structure interaction between nearby piled buildings under seismic excitation by bem-fem model

Simplified discrete systems for dynamic analysis of structures on footings and piles

The purpose of this paper is to study the relative significance of kinematic and inertial interaction on the magnitude of forces induced in pile foundations by a seismic disturbance. The structure is modeled as a single-degree-of-freedom (SDOF) oscillator and the foundation is a typical pile group embedded in a homogeneous half-space. A three-dimensional Green’s function-based formulation, which rigorously models the pile-soil-pile interaction, is used to calculate the forces in the piles during the seismic kinematic- and inertial-interaction phases. Different structures, represented by their aspect ratios and natural frequencies, and different pile foundations, characterized by their pile rigidities and spacings, are considered in this study. The results show that the seismic shear force and bending moment in a pile are strongly contributed by the kinematic seismic interaction, except in a band approaching the natural frequency of the pile-soil-structure system. In this frequency band, the inertial interaction dominates the pile forces. The extent of contribution from the inertial interaction is governed by the damping of the foundation.

Forces in pile foundations under seismic loading

The paper presents results of a study on the harmonic response of piles and pile groups embedded in a halfspace to various forms of seismic waves. These include the Rayleigh wave as well as obliquely incident P, SV and SH waves. The pertinent mixed boundary value problems of pile-soil-pile interaction are solved by a numerical model of the boundary integral nature. All modes of foundation vibrations, i.e. translational, rocking and torsional, are included in the model. The results presented are used to highlight the salient features of the seismic response of piles. In addition, the influence of certain pile-soil parameters, such as pile rigidity and pile spacing, on the seismic behaviour of pile foundations is investigated.

Response of pile foundations to rayleigh waves and obliquely incident body waves

A simple analytical solution is presented to calculate the single-pile response when excited by the passage of Rayleigh seismic waves. Closed-form expressions for the horizontal and vertical displacement distributions are presented for piles with finite or infinite length. The analytical results for both free-head and fixed-head piles are obtained through a dynamic Winkler model, with realistic frequency-dependent ‘springs’ and ‘dashpots’. The results of the presented method are in excellent agreement with results of a rigorous solution. It is shown that in vertical motion, the differences between pile and soil displacements are far more significant than in horizontal motion, and therefore, further work is needed to investigate the importance of pile-soil-pile interaction (group effects), because of the vertical component of Rayleigh seismic waves.

G.A. von Arx

Papers

Seismic analysis of the pile foundation of the reactor building of the NPP Angra 2