Sliding, Launching and Rolling

Cass Hayward has designed many bridge installation schemes involving special techniques including launching, rolling and sliding. Over the years the equipment has evolved and we have experience of various types of both skids and rollers and similarly of propulsion using both winches and a variety of jacking systems. A notable feature of our transverse railway bridge slide for the River Exe Viaduct outside Exeter St David’s station was the use of ball bearings in tracks purpose-fitted to the substructure as a permanent feature. Our design for roll-in of the concrete viaduct near Waterloo station was unusual in that the roll path was at ground level with skids fitted to the underside of support columns.

The girder launching for our A249 Sheppey Crossing viaduct achieved a maximum 93m long curved freestanding cantilever of 93m on a curved plane and with four girders on skids in the cross section. Other previous launches had shorter but significantly long cantilevers e.g. 65m for Loughor Bridge Swansea and we were engaged as advisor and independent checker of the launch design for CrossRails’s recent Stockley Park viaduct construction.