Seismic behaviour of an in-service curved PC box girder bridge with prestressed concrete piers – preliminary analyses

Codes and design loads have changed over time and a large number of existing in-service bridges could not satisfy current static and seismic standards. In particular, a significant part of bridge infrastructures was built in the second half of the 20th century, frequently neglecting the earthquake action. Therefore, the response under seismic actions of these structure should be investigated, especially for reinforced and prestressed concrete bridges which represent the larger part of the existing infrastructure system. In this study, the seismic response of a case-study post-tensioned concrete bridge is evaluated. The bridge deck is a curved continuous box girder built with precast segments using the balance cantilever construction method, supported by eight prestressed concrete piers. A hinge joint in the middle of the central span divides the continuous deck in two parts. In order to investigate the effect of the prestress in the piers on the seismic behaviour of the structure, a global FE model of the bridge was developed. Geometry and properties of structural elements were obtained from design documentation. Non-linear time-history analyses are then performed, considering different assumption related to the prestressing force in the piers and the damping of the structure. Results in terms of displacements are then critically discussed, comparing the different cases considered.