Structural Monitoring and Rehabilitation of a Gerber Bridge

Many existing reinforced concrete bridges exhibit behavior at the Service Limit State and the Ultimate Limit State which can be considered unsatisfactory with respect to the current provisions of Codes, due to deficiencies deriving from obsolete calculation methods, ageing, material degradation, diffuse or localized corrosion and increased loads. Among these, cantilever concrete bridges with half-joints, also called Gerber bridges in Europe, may present a decrease of safety conditions for the most stressed current sections of the deck or for local potential failure mechanism of critical members, that affect the performance of elements sensitive to degradation, such as Gerber saddles. To perform vulnerability assessment, the validation of FEM models against on-site tests and investigation is of fundamental importance for acquiring information on the constraint conditions, verifying the structural scheme by identifying the degree of collaboration between the structural elements and identifying the state of cracking or damage. Thus, for a case of study the results of a structural assessment performed with Finite Element model are presented through validation with on-site tests. Then, a simple strengthening intervention through external prestressing which changes the structural behavior in service life, is implemented without the need to recourse to interventions of greater impact, obtaining an improvement of the overall performance. The results of monitoring and on-site load tests are presented as the validation method for the analyses on different FE models together with the proposed intervention.