Hybrid simulation of an old reinforced concrete viaduct based on nonlinear substructuring techniques

The seismic performance assessment and retrofit of an underdesigned 400m span viaduct by means of continuous-time hybrid simulations was conceived within the SERIES European RETRO TA project. In detail, two of the twelve piers - Physical Substructures - will be loaded through dynamic actuators at the Joint Research Centre of Ispra, Italy, whilst the remaining ten piers and the deck as well - Numerical Substructures - will be numerically modelled and solved. Time history analyses conducted on a refined Finite Element OpenSEES fiber model of the bridge highlighted appreciable nonlinearities of the pier dynamic responses already under the Serviceability Limit State earthquake level. Nonetheless, implementation issues relevant to the typical execution time of the NS - few milliseconds - make complex FE fiber models not suitable for testing purposes. In this paper, a rational model reduction of nonlinear refined OpenSEES fiber-based piers is suggested as an extension of the Guyan method. Relevant numerical results are presented and commented.