Unseating Risk of a Continuous PC Box-Girder Bridge: Experimental Monitoring and Numerical Analysis

A peculiar problem occurred in the Furiano viaduct, a continuous prestressed concrete (PC) box-girder bridge (890 m long) of the A20 highway in Sicily, Italy. This viaduct is exhibiting large sliding displacements on the bearings pertinent to the “movable abutment”, almost approaching the maximum allowable stroke (in relationship to the installed plate) and causing the rupture of the overlying expansion joint. This accident was plausibly due to an erroneous placement of the bearings in the construction phase. The viaduct was then closed to the traffic as a precautionary measure, and a monitoring system, consisting of temperature and displacement sensors providing synchronous measurements, was implemented in situ. In this paper, we shed light on the technical causes of the expansion joint collapse, and we investigate the unseating risk (i.e., the bearings fall beyond the support plate) via experimental data accompanied by analytical evaluations of long-deform deformation phenomena (shrinkage and creep) and comparisons with numerical thermal-induced movements obtained from a finite element model incorporating the mild curvilinear configuration and the statically indeterminate nature of the bridge.