Seismic retrofit of a prestressed concrete road bridge by deck isolation with friction pendulum devices

The paper deals the proposal of seismic retrofit intervention for an existing multi-span prestressed concrete road bridge, achieved by the use of Friction Pendulum System (FPS) as isolating system located between piers top and deck. A design process consisting of an appropriate application of capacity-design principles as well as the Direct Displacement-Based Design approach was implement-ted. To assess the impact of the FPS nonlinear behaviour on the bridge performance, a device model that can represent the variation of the normal force and friction coefficient, bi-directional coupling and large deformation effects during nonlinear dynamic analyses is used. The paper examines the effects of the modelling parameters on the seismic response of the retrofitted bridge evaluated through nonlinear time-history analyses involving a solution of the complete set of equilibrium equations at each time increment. The results obtained highlight the effectiveness of the seismic retrofit strategy