Pounding between bridge decks. Computational details and results

The observation of damage to structures, either buildings or bridges, due to earthquake induced pounding, dates back to early San Fernando (1971) and Mexico City (1985) post-earthquake reconnaissance reports. Recent ground shakings that have struck Italian territories have renewed the awareness of the necessity to clarify some aspects related to the pounding-induced forces acting on the bridge and viaduct piers. Historically pounding has been studied by either of two approaches, that are: 1) the stereo-mechanical approach, based on the physical laws of the impact phenomenon and the definition of a restitution factor, and 2) the force-based approach, based on the definition of the local force due to impact. Moreover, impact can be either soft or hard, depending on the amount of earthquake-induced energy dissipated locally through the damage of the colliding bodies. In this study, pounding response of two linear SDOF (Single Degree Of Freedom) systems has been studied through different models, namely: 1) Linear Spring, 2) Kelvin-Voigt, 3)Hertz, 4) Hertz-damp and 5) Stereo-mechanical model. Those models have been applied using both backward and forward spectrum-compatible and artificially generated ground motions. After introducing 1) the details of each of those models, 2) the main differences among them, and 3) the numerical computational strategy implemented, the main results are presented. Among these latter, being the early results of an exploratory and propaedeutic work for a Doctoral Thesis, the pounding-inducted response spectra, either in terms of peak displacement or pounding force, are developed.