The project aims to replace the bearings of the viaduct, following the detection of deformations in the elastomeric bearings and exhaustion in the sliding POT bearings. The interventions seek to ensure the durability and structural safety, extending the viaduct’s service life by more than 50 years.

The viaduct characteristics are:

• Total Length: 700 m, divided into two lateral isostatic spans of twin box girders with spans of 40 m, and a central box girder span built by cantilever method with spans of 45-90-45 m.
• Height over the Ulla River: Over 60 m.
• Central Piers: Equipped with fixed POT bearings.
• Piers at the end spans: Aligned with the expansion joint between sections, supporting the box girders with elastomeric bearings and the sliding POT bearings of the in-situ section.

A 2023 inspection by INES detected deformations in the elastomeric bearings and exhaustion in the sliding POT bearings. A detailed topographic survey was conducted to study the permanent deformation of the piers, as well as a comprehensive geometric study of the pier head caps using mountaineering techniques due to the difficulty in accessing the pier head caps.

The scope of work can be detailed as below:

• Inspection and Diagnosis: Includes a detailed structural analysis to assess the performance of the bearings and the displacements they are subjected to.
• Bearing Replacement: New spherical bearings were installed due to their ability to accommodate greater displacements and lower maintenance requirements.
• Structural Reinforcement: Reinforcement measures were implemented in the piers and deck, and a stopper device was installed for the controlled release of pier deformations.
• Lifting and Replacement Process: The process included controlled recovery of the sliding piers, the replacement of elastomeric bearings, and jacking of the POT bearings, using jacking forces of 3300 kN on the prefabricated deck side and 1200 kN on the in-situ deck side.

The newly installed bearings are elastomeric on the box girder side and spherical on the in-situ span, chosen for their extended displacement capacity and low maintenance, guaranteeing a remaining service life of over 50 years. These bearings allow for significant movements without compromising the structural integrity of the viaduct.

The project was coordinated between Globalvía’s engineering services and Freyssinet specialists, who adapted the design to the complex conditions of the existing structure. The quality of the information provided about the viaduct, from the original project to the periodic inspections, facilitated the planning and execution of the work. During the works, temporary detours and traffic restrictions were implemented to minimize the impact on AP-53 users and ensure road safety.

This project is part of a comprehensive maintenance plan for road infrastructures. The replacement of the bearings ensures the safety and extends the service life of the viaduct, allowing its operation under optimal conditions for several more decades.