1. ECCOMAS Thematic Conference - COMPDYN 2015
Finite Element Simulation of Wave Propagation in Nonlinear Soils
Theofilos Manitaras
1*
, Manolis Papadrakakis
1
1
Institute of Structural Analysis & Seismic Research
National Technical University of Athens
Zografou Campus Athens 157 80, Greece
teojgor@gmail.com, mpapadra@central.ntua.gr
ABSTRACT
In this paper, the finite element solution of wave propagation in soils exhibiting nonlinear behavior is
presented. An enriched Ramberg-Osgood constitutive model, consistent with the extended Masing behavior
is used. The above model, accounts for the hysteretic behavior of soils which is evident and of primary
importance in cyclic loading conditions. Calibration of the model constants is achieved by fitting to
theoretical or experimental shear modulus reduction and damping curves via an optimization procedure. A
multiaxial generalization based on the octahedral shear strain is applied. The computational procedure and
the relations used to calculate the constitutive tangent tensor and its matrix form, used to achieve quadratic
rates of convergence and minimize the number of iterations of the Newton-Raphson algorithm are also
shown. In order to take into account the extent of the computational soil domain to infinity, absorbing
boundary conditions of the type proposed by Lysmer are applied to appropriate nodes of the finite element
mesh. In addition, accurate calculation of the effective nodal forces of the stress waves induced by a given
ground motion are evaluated. Comparison is made with the results produced by using different implicit
direct time integration schemes. Applications ranging from one-dimensional shear wave propagation to
three-dimensional geometries are demonstrated. They include excitation of the soil with simple wavelets as
well as complete seismic motion records of past earthquakes. Finally, best practices for successful
simulation are summarized.
Acknowledgements
The first author acknowledges support from the Bodossaki Foundation. This work has also been supported
by the European Research Council Advanced Grant "MASTER - Mastering the challenges in numerical
modeling and optimum design of CNT reinforced composites" (ERC-2011-ADG_20110209).
Powered by TCPDF (www.tcpdf.org)