Stochastic Finite Element Pile Settlement Analysis Under Dynamic Loading

Abstract eng:
With the spectacular increase of computing power and the advances in simulation methods, it is now possible to investigate realistic geotechnical problems in the framework of the stochastic finite element method [1,2]. In this paper, a 2D pile settlement problem is treated considering the spatial variability of the stiffness of the soil. The pile is modeled with beam elements while the soil is modeled with four-node quadrilateral plane strain elements. The spatial variability of the elastic modulus of the soil is described by a homogeneous non-Gaussian stochastic field with statistical characteristics derived from experimental data. The soil-pile system is subjected to natural seismic records corresponding to various levels of seismic intensity. The response variability is computed using Monte Carlo simulation. Parametric investigations are carried out examining the effect of probability distribution, coefficient of variation (COV) and correlation length of the stochastic field on the settlement variability. In the static case [3], the settlement COV starts from small values for small correlation lengths (wide-banded stochastic field) and tends to large values for large correlation lengths (random variable case). A magnification of uncertainty is observed in the case of large input COV(>50%). In the dynamic case, the response COV of a frame structure has been found to vary significantly not only with the correlation length but also in many different ways among the records of the same intensity level [4]. In order to examine the differences in settlement variability between the static and dynamic case, a comparison of the results in [3] with those obtained from a nonlinear dynamic analysis of the soil-pile system is finally performed. References [1] G. Stefanou, The stochastic finite element method: past, present and future. Computer Methods in Applied Mechanics and Engineering, 198, 1031-1051, 2009. [2] D.V. Griffiths, G.A. Fenton, Probabilistic settlement analysis by stochastic and random finiteelement methods. J. of Geotechnical and Geoenvironmental Engineering (ASCE), 135, 16291637, 2009. [3] G. Stefanou, G. Pittos, M. Papadrakakis, Stochastic finite element pile settlement analysis. Proc. of the 4th European Conference on Computational Mechanics (ECCM 2010), Paris, France, May 16-21, 2010. [4] G. Stefanou, M. Fragiadakis, Nonlinear dynamic analysis of frames with stochastic nonGaussian material properties. Engineering Structures, 31, 1841-1850, 2009.

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