Ndt tests on an existing r.c. bridge: how to manage different test campaigns

An interesting case study is discussed in this paper that could represents a yardstick in the approach to an existing structure. In this case an isostatic (Gerber scheme) prestressed r.c. bridge is considered; this scheme is quite usual for simple bridge. In present paper a particular situation is discussed. The bridge was built in 1970 as an element of a series of similar bridges. During his service life it suffered poor structural maintenance and it shown transverse and longitudinal displacements that were considered unacceptable for its use. So four series of different structural tests (both non destructive and partial destructive [concrete cores], both static and dynamical load) were carried out. Results of these tests are evaluated independently each other by different Authorities and regardless real structural scheme and viscous behaviour in concrete. So wrong conclusions were carried out and in 2012 the bridge was assumed near collapse. In 2013 the Local Authority (Chieti Municipality) ordered a new series of static test and structural analysis. By means of a correct management of previous results and coherent, but simple, structural model, it had possible to detect a security level that is adequate to original design provisions and to previous Code. A simple recalibration of load capacity was carried out, according to actual structural Code. Now the bridge is on duty regularly and a maintenance program will start in the near future.