This mature-structures winner is unusual in that it is not one particular structure but a component to be found in bridge structures around the country, namely the prestressed-concrete bridge beam.
The beam is hugely successful. Of the DoT's 9000 bridges on motorways and A roads, some 6000 are of concrete and of these some 4500 have been built using prestressed-concrete bridge beams. Key to the success of the beam was the recognition by the Prestressed Concrete Development Group of the need for standardisation to simplify design and keep manufacturing costs low. The original standard beams were the inverted T, the I-beam and the box-beam. These were joined in the mid-1960s by the M-beam, and by the U-beam in the early 1970s. More recently, the Y-beam range has been introduced which should eventually replace the M-beam and inverted T-beams.
The higher quality concrete needed to take advantage of high-strength prestressing steel has led to precast prestressed beams being acknowledged as the most reliable of bridge components in the 5-35m span range.
OWNER Highways Agency
SUPPLIERS C V Buchan
DEVELOPMENT Prestressed Concrete Association