The application of the hyperelasticity constitutive relationships for modelling of elastomeric bridge bearings is presented. Elastomers which are used for bridge bearings are nearly incompressible materials. Consequently, two models of hyperelasticity for rubber-like materials, i.e. neo-Hookean and Yeoh models are considered. The neo-Hookean model is the simplest possible model of hyperelasticity but unfortunately it has a number of disadvantages (i.e. at certain deformation modes it gives physically unreasonable predictions). The Yeoh model for nonlinear elastic materials is superior to neo-Hookean model and leads to rational description of the behavior of the elastomers for significant elongations and is implemented in many commercial programs using finite element method (FEM). In this work, ABAQUS program is utilized for modelling of chosen bridge bearings. The parameters of two constitutive models are determined based on experimental results and are used in numerical calculations for selected examples of bridge bearings. Concluding remarks are drawn and directions of future research are outlined.

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This work concerns mainly the finite element (FE) implementation of polyconvex incompressible hyperelastic models. A user material subroutine (UMAT) has been developed and can be utilized to define the aforementioned material behaviors in the FE system ABAQUS. The subroutine is written using a novel strategy in order to maximally simplify the relations for the analytical material Jacobian (MJ). The UMAT code is attached in the appendix. The developed subroutine allows to significantly decrease the time of computations and to avoid possible convergence difficulties. The structure of the code enables modifications which may lead to a rheological, damage or growth models, for instance.

A parametric model for foam-like materials is proposed and its correlation with experimental results is analyzed. The class of foam-like materials is assumed to be described by an isotropic elastic potential based on a general model proposed by Ogden. The class is parametrized using the relative mass density of the material. Functional relations between material parameters and the relative mass density are obtained from experimental data. A simple application problem, namely the optimization of a foam for maximum energy absorption under homogeneous compression, is formulated and solved numerically. [S0021-8936(00)02802-6]

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