Seismic assessment and retrofitting of existing railway bridges

The earthquake response analysis of typical existing bridges for high speed railway was carried out through linear and nonlinear dynamic analyses using refined finite element three-dimensional lumped-plasticity models and multiple component ground motions. The seismic vulnerability of such bridges was assessed through local and global response quantities. The retrofitting scheme adopted to augment the earthquake performance of the sample bridge structures is the base isolation system comprising either lead rubber bearings or steel dampers. The present analytical study investigates and compares the response of such isolation devices. The outcomes of the numerical analyses proved that the use of base isolation systems lowered significantly the seismic demand, especially on the bridge piers and the foundation systems. Hysteretic metallic devices were found more suitable for the seismic isolation of railway bridges. Additionally, the need to comply with the serviceability requirements is found to be more stringent for the base isolation system in the design of retrofitting schemes for railway bridges than the fulfillment of the ultimate limit state. Further work is ongoing to account for the nonlinear modeling of the rail on the global response of base isolated railway bridges under multiple earthquake components