Cass Hayward has been closely engaged with the development of Network Rail’s standardised designs for bridges (SDD’s) and this involvement dates back to an appointment from British Rail in 1989 to update the 1975 (Western Region) trapezoidal box girder underbridge range for compliance with BS5400.We were then engaged as independent checker of the updating of the Zed girder designs. In 2006 we were appointed by Network Rail to conduct a review of all existing and potential ranges of underbridge designs and in 2008 to update again the trapezoidal box girder designs. In 2009 we won a design competition to propose and develop a Network Rail standard range of railway over-line bridge designs.
We regularly adopt the standard designs for live projects with the box girders, U decks and footbridges most regularly used. The current Network Rail U deck range is a standard developed as recommended by our 2006 study and is based on the design Cass Hayward conceived for UK application in 1996 as a modern improvement to the zed range. Our early U deck projects came to fruition as commercially attractive Contractors’ offers and quickly proved popular with the railway authorities. The first of the current type was installed as a two track single span at Appleby in 1997 and we further developed the design for twin span use for a reconstruction at Kennishead near Glasgow in 2003 and with a three span version for two adjacent similar river bridges at Black Rabbit and Peppering near Arundel in 2009.