A new material for railway bridges : variable thickness plates

After being extensively used in railway bridges until the 2nd world war, steel products suffered a decline in Europe until the late seventies.The TGV Nord (French high speed train between Paris and Lille as well as between Paris and UK via the Channel tunnel) signalled the rebirth of steel use in railway bridges.This surge in metallic structures is related to the development of composite bridges (steel/ concrete) which nowadays are the dominant type.The economic edge of composite bridges originates from productivity improvements by the fabricators as well as development of new steel products such as variable thickness plates which are plates whose thickness varies lengthwise and therefore make it possible to manufacture girders closely matching the bending moment distribution.