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Modelling and analysis of high-damping rubber bearings for the seismic protection of bridges

Grant, DN; Fenves, GL; Auricchio, F; (2005) Modelling and analysis of high-damping rubber bearings for the seismic protection of bridges.

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High-damping rubber (HDR) bearings are used in seismic isolation applications for buildings and bridges, although no models are currently available for the accurate description of the shear force–deformation response, including the effects of strain-stiffening and strain-induced degradation, under bidirectional loading. A strain rate-independent, phenomenological model is developed which effectively represents the stiffness, damping, and degradation response of HDR bearings, for use in seismic analysis and design applications. Calibration of the model is carried out over a series of bidirectional test data, using the downhill simplex algorithm to obtain a set of material parameters for the bearing. Existing design procedures for seismically isolated bridges provide inconsistent recommendations, particularly for the design of piers. A design methodology that targets performance goals at two levels of seismic hazard is developed, as an extension of existing displacement-based design methods. The design method aims to ensure that pier inelasticity is prevented at a “design” seismic hazard level, and is limited to a specified ductility for “maximum credible” hazard. Finally, a series of parametric studies is carried out, using simple isolated bridge geometries, the proposed bearing model to represent isolator response, and bidirectional ground motion input scaled by a range of scaling factors to assess the effects of bidirectional input and variable seismic intensity on isolated bridge response. The studies show that the nonlinear behaviour of HDR bearings reduces the bearing displacement demand at high intensity levels, at the expense of increased ductility demand in the piers, particularly compared to the response ofother bearing types. The multiple performance level design approach is also assessed in the parametric studies, and it performs adequately for simple bridge configurations; the method will, however, require modification to account for the effects of superstructure flexibility and more complicated bridge geometries.

Title:Modelling and analysis of high-damping rubber bearings for the seismic protection of bridges
Additional information:keywords: Bridges, By me, Isolators, Material modelling
UCL classification:UCL > School of BEAMS > Faculty of Engineering Science > Civil, Environmental and Geomatic Engineering

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