Sign gantries, consisting of prestressed beams and reinforced columns, are being used on motorways and major roads. Depending on the cross-section of the beam used, spans up to 41 metres can be achieved, sufficient for he gantry to span across both carriageways of a motorway. The units offer fast and economic erection, which is a particular advantage when they are being installed on a ‘live’ road.
The columns are placed in preformed sockets in the foundations; if required these can be designed to be demountable so that the complete gantry can be removed and reused elsewhere. The beams are provided with the necessary fixings for the signs already cast in.
For further information see Current Practice Sheet 147, Concrete gantries, published in CONCRETE, March 2006, p 20. Copies are available as free downloads from the Members´ area of the Concrete Society web site and from the Concrete Bridge Development Group web site (www.cbdg.org.uk).