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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.

but also weld sequencing or treatment measures before and after welding [2, 3]. This shows the complexity in estimation of post-welding imperfections being of interest here. This specific study refers to I-shape sections welded by conventional arc welding processes. However, similar considerations apply to other cross-sectional shapes showing the substantial need of further research in this field. Girders are typically manufactured under workshop conditions and assembled on site.

This paper discusses different aspects of analytical and numerical modelling of the buckling resistance of welded I-section columns subjected to axial compression. The section considered is of class 1 that implies no local buckling affecting the column performance. The proposed analytical formulation of the buckling resistance is based on the so-called Marchant-Rankine's-Murzewski approach (M-R-M approach). The model proposed is of a 2D type and is a simplification of the 3D one that has recently been presented by the authors. The parameters of equivalent stress-strain model of the postwelding steel are calibrated in two stages of the best fit approximation procedure and with use of numerical results of the finite element simulation of the buckling resistance. In the first stage, the postyielding inelastic tangent stiffness parameter ξE,eff is evaluated with fixed value of the first yield parameter ψeff= ψcom. A target of the second stage is to assign the best fit value of the first yield parameter ψeff and the imperfection factor n that allows for accounting the effect of geometric imperfections.

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This paper attempts to verify the Eurocode's buckling resistance criteria in case of rolled I-and Hsections in monoaxial bending about their major axis using finite element simulations and two imperfection modelling techniques, namely a) using the equivalent geometric imperfection concept in which the effect of material and geometrical imperfections is represented by an equivalent minor axis bow amplitude and the lowest eigenmode imperfection profile, and b) the separate inclusion of material and geometrical imperfections. In the latter approach, material imperfections are based on the standard rolled residual stress patterns consisting of compression/tension peak values dependent upon the h/b ratio. Moreover, the geometric imperfections are included as the tolerance limit of steel I-section rolled products. Common and higher grades of steel products are considered. The finite element shell model is utilized and built within the ABAQUS software. The Eurocode's resistance criteria are verified by using the results of FEM simulations. An impact of the moment gradient on the member buckling resistance as well as the plateau limit evaluation and the resistance increase as a result of large twist rotations accounted for are assessed. Remarks in relation to analytical formulations presented in Eurocode 3 are drawn.