Towards a Standardized Design Structure for Concrete Tramways in Flanders

For more than ten years tramway structures in Flanders have been built in concrete, particularly those which are subject to traffic loading by trams and city buses. As there has never been a standardized design, a wide range of different solutions have been tried, either in jointed concrete slabs with or without additional steel reinforcement, or in continuously reinforced concrete (CRC). Some of the solutions were successful; others failed. The central engineering department of the Flemish public transport company "De Lijn" has taken the initiative to evaluate the different solutions and to move towards one or more standardized design structures. One of the difficulties is that different solutions for the positioning of the rails need to be considered - according to different commercial suppliers -, and this has an impact on the structural solution for the concrete layers. In general, the structure consists of a base layer and two layers of concrete. The bottom layer, mostly in conventional concrete C30/37, is the bearing structure for the rails. The top layer, normally in pavement quality concrete, is the running surface for buses. Typical technical details to be dealt with are the spacing of joints in the narrow concrete slabs, the reinforcement in the top or bottom part of the concrete top layer, the bond or separation between the two concrete layers, and the layout of steel reinforcement and anchoring abutments in case of CRC.