Assessment and strengthening of post-tensioned concrete box-girder bridges

Post-tensioned concrete box girders have been widely adopted for the construction of medium- to long-span bridges since the mid-20th century. Since the construction of the first such bridges, there has been rapid growth in the volume and weight of heavy vehicles, as well as an increase in exposure to adverse environmental conditions. At the same time, it is estimated that more than 50% of existing bridges in higher-income countries are over half-way through their design life and thus bridge owners are challenged with the management of aging structures. When deterioration in prestressed concrete bridges is identified during inspections, it leads to specific assessments and is usually followed by the need for bespoke strengthening design solutions. In many cases, the challenge in implementing the strengthening resides in maintaining structural capacity to minimise traffic disruption before the works are complete. This article covers the technical and asset management aspects related to the assessment and subsequent strengthening design for post-tensioned concrete box-girder bridges through the lens of case studies on two successful post-tensioned bridge rehabilitations. The strengthening solutions presented have been implemented with minimal disruption to traffic and have had a positive environmental impact by avoiding demolition and full deck reconstruction.