High Damping Rubber Bearing (HDRB) isolating devices fornuclear power plants: FE modelling and damage characterization

The work describes the research activity performed at Politecnico di Milano within the field of seismic isolation of nuclear power plants buildings, during which the development of FE models in ANSYS® has been pursued along with the definition of a reasonable limit state failure domain under seismic excitation. A refined FE model of a single thin rubber layer was developed to investigate the capabilities, in terms of convergence and goodness of fit, multiple Ogden, Polynomial and Mooney-Rivlin hyperelastic material models, tuned against laboratory tests on rubber specimens. Subsequently, a complete FE HDRB model, closely representing the alternate rubber and steel layers, was set using the best 3 material models, derived from single rubber layer analyses. Specific scopes of the performed activity are: 1 – developing, tuning and testing a robust FE model for a HDRB, with specific care on material constitutive law; 2 - evaluating the reliability of an analytical approach developed by the Authors, proposing a stress field in the rubber layer; 3 - identify limit state conditions for “first damage"