Pianturino Viaduct - Stability Analysis of Anchored Structures

The Pianturino Viaduct is located along the N02 road, near the Cadenazzo Municipality. It was built between 1978 and 1980. It is a reinforced concrete structure with 3 spans (55-70-55 m) crossing the valley of the same name at about 70 m above the valley bottom. The project provided for the use of permanent pre-stressed anchors to ensure the stability of the protection walls of the pier foundations and the retaining structures of the abutment on the Chiasso side. In 1992, the anchored structures were subjected to extraordinary maintenance consisting in the integration of new anchors. Following the general inspection in 2019, FEDRO commissioned Lombardi SA to conduct a study with the aim of quantifying to what extent the stability of the slopes and anchored structures depend on the current state of preservation of the anchors. The methodological approach adopted was based on the logical sequence foreseen by SIA 269 and on the procedural approach of FEDRO Directive 12005. The updating information phase included the general examination of the structures, definition of the conservation state of the anchors and updating the geological-geotechnical reference model. The updated geotechnical and structural verifications of the anchoring elements showed that, with reference to the safety levels required by the regulations in force and the residual service life of the viaduct, the stability of the slopes and the structural safety of the works depend on the contribution of the prestressed anchors. Given the impossibility of establishing the ultimate anchor strength, linked to the evolution of the degradation processes of the system (reinforcement and header), retrofitting of the anchored structures was proposed in relation to two types of approaches: preservation of the existing and replacement of the anchors, respectively. Different investment scenarios related to the remaining service life were provided to the client.
Reference location
Final client
Federal Roads Office FEDRO, Bellinzona
Is Consortium
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Consultancy; Monitoring / Safety / Operation / Maintenance; Special studies