Bridges

The current bridge design code, AS5100.5-2004, adopts concrete strength grades between 25MPa and 65MPa. The upper limit of 65MPa was an increase from 50MPa in the Austroads Bridge Design Code, 1992. Before that, the NAASRA Bridge Design Specification, 1976 had an upper limit of 30MPa with permission to use a higher grade in precast reinforced concrete made in factory conditions.

The new draft published for public comment in January 2014 proposes to allow up to 100MPa.The reason for limiting maximum strength in earlier codes was the lack of sufficient research on high strength concrete.

This paper discusses the impact of adopting high strength grade concrete in the design and construction of segmental box girder bridges, particularly under serviceability limit state conditions.