ACCOUNTING FOR NONLINEAR SOIL WITHIN DYNAMIC SOIL-STRUCTURE INTERACTION CALCULATIONS IN EARTHQUAKE ENGINEERING

Abstract eng:
The performance of more accurate simulations that account for new physical phenomena at stake arises as an interesting way for the assessment of structural seismic resistance. In this framework, the present work deals with the numerical modelling of nonlinear dynamic soil-structure interaction. Dynamic soil-structure interaction problems are usually solved using a sub-structuring technique where the soil-structure system is decomposed into two sub-domains: the nonlinear superstructure and the linear (visco)-elastic unbounded soil. The superstructure might include, in addition to the actual structure, a part of soil showing a nonlinear behaviour. To address this problem, a BEM-FEM coupling strategy is adopted in this work. On one hand, the superstructure is modelled by a FE method which enables to account for nonlinear constitutive laws as well as complex geometries in a straightforward way. Besides, the problem within the superstructure is formulated in the time domain. On the other hand, the interaction forces coming from the linear unbounded soil are represented by means of an impedance operator defined on the soil-superstructure interface and computed with a Laplace-domain BE method. This hybrid Laplace-time domain approach [1], which contrasts with more classical frequency-based formulations [2], uses convolution quadratures-based techniques [3] to evaluate the interaction forces in the time domain. In order to bring out the main features of this approach, a nonlinear application is assessed and compared to a full-FEM solution. It deals with a 3D model of a reinforced concrete building founded on a nonlinear soil. A global damage constitutive law is chosen for the structure [4]. The elasto-plastic soil Hujeux constitutive law [5], well-adapted for cyclic loadings, is adopted for the soil.

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