Multilevel evaluation procedure for the demolition of prestressed concrete bridges: the case of the Kalix bridge in Northern Sweden

A carefully studied evaluation was necessary to replace an existing pre-stressed concrete box girder bridge that had been in service for over 60 years, in Kalix, Northern Sweden. The bridge was 283.6 m long divided into five spans, and it was constructed using the balanced cantilever method. The decision to replace the old bridge created the need to evaluate a demolition procedure for it, one carefully designed not only to avoid damaging the newly built bridge or creating stability-related issues, but also to prevent any debris from falling into the Kalix River, which is part of a Natura 2000 protected area. This article focuses on the comprehensive methodology, on the demolition design, and on the observations related to residual prestress levels in the bridge, indirectly obtained through a reversed-engineering FEM process and on the limitations of the demolition technology to be used in these specific cases. Several variables were monitored during the deconstruction process, to control the structural stability better during all the phases of the project. The main outcome of the full condition assessment is that it provides the information needed to make informed decisions for interventions on these types of structures.