Post-tensioned bridges: special inspections

This chapter provides a background to the development of post-tensioned concrete in UK bridges and addresses some of problems and defects that have come to light as those bridges have aged. Learning from failures, such as that of the Ynys-y-Gwas bridge in 1985, bridge owners identified the need to have detailed intrusive inspections of post-tensioning systems and this is the focus of much of the chapter. Such inspections are now required by the Design Manual for Roads and Bridges and should be an important part of a bridge manager's responsibilities.

The construction of reinforced concrete structures was well advanced by the early decades of the twentieth century, and many such structures from that period survive to this day. However, it was realised that the performance of concrete could be improved if reinforcing bars could be initially tensioned before loading the structure with self-weight and traffic, thereby keeping the concrete in compression.