Bridge retrofit di un ponte stradale in cap in accordo con le NTC2008

The paper deals the proposal of a procedure for the seismic retrofit of existing prestressed concrete bridge built on "Domitiana" state road in Campania district. Starting from the identification of the bridge structural geometry and of the material mechanical properties based on the original project designs, the seismic vulnerability assessment of the existing bridge was carried out. At this aim a Nonlinear Static Procedure (NSP) based on the Capacity Spectrum Method (CSM) and on Inelastic Demand Response Spectra (IDRS) was applied. According to the Performance-Based Earthquake Engineering (PBEE) principles, these procedure allows to correlate explicitly the different levels of performance to varying intensity of seismic action. Then a seismic protection strategy based on the insert of isolating system between pier top and deck was implemented. A design process consisting in an appropriate application of capacity-design principles and of Direct Displacement Based Design (DDBD) approach was applied. Finally the seismic response of the bridge, modelled with an “exact” damping matrix, was evaluated through a nonlinear time-history analysis with a direct integration of motion equation using a set of recorded accelerograms whose spectra are consistent with the design spectrum proposed by the Italian Code.