resilient baseplate

The rail is fixed to the reinforced concrete plinth or slab by means of a baseplate assembly. The rail is fastened to the baseplate by a clip and the baseplate is held down to the plinth by a holding down bolt, usually grouted-in or fixed with epoxy resin. Within the baseplate assembly are a rail pad beneath the rail and a resilient pad to provide elasticity. A number of proprietary systems are available throughout the world, with the key European manufacturers being Pandrol (UK) and Vossloh (Germany).

 

The Vossloh System 300 fastener is in widespread use for slab track (or ballastless track) systems throughout the world. In the Vossloh assembly, the rail is held down to the baseplate by a spring clip. A bolt passes through the spring clip providing tension in the fastening system. In the System 300, these bolts also serve to anchor the baseplate to the plinth.

Direct fixing and resilient baseplate systems have been used widely throughout the world as a system for reducing the dead weight of track on bridges. In its early form, the elasticity was provided by mounting standard baseplates onto timber bearers. This can be seen on London’s Underground network. Over the last 20 years the use of concrete plinths/slabs with resilient baseplates has been favoured, for example on the Kuala Lumpur LRT and Docklands Light Rail.

Turnouts and rail expansion joints are available to suit resilient baseplate systems.

 

Traditional construction for baseplate systems has been “bottom-up” where the concrete slab is cast first. Baseplates and rails are then set up to the correct alignment before fixing by drilling and grouting beneath the baseplate.

On the Berlin to Hanover high speed line a continuous length of resilient baseplate track was slip-formed, profiling the concrete to take the IOARV 300 fastener. This system was developed as an evolution of the Rheda cast-in sleeper system and features a slab rather than two discrete plinths supporting the rail.

The Vossloh System 300 fastener has the capacity for adjustments of 30mm vertical and 20mm lateral adjustment. This means that minor variations in the slab geometry can be accommodated in the fastening assembly.

“Top-down” construction allows the slab to be cast in situ around the baseplates and fixings. This technique was used at St. Pancras.

As an alternative to in situ slab or plinths, pre-cast sections can be used. The FF Bögl system has been successfully installed on the high speed Nuremberg to Ingoldstadt lines in Germany. Again based on the Vossloh System 300 fastener, pre-cast slabs are manufactured and then finished to the required alignment tolerance using laser technology. On site, the slab sections are aligned and fitted together using a locking bolt system.

 

The technology for the baseplate fastening systems and plinths is well developed, with acoustic performance well documented for conventional rail and light rail on structures. By varying the rail and baseplate pads, a broad spectrum of resilience is available allowing the track to be “tuned” to suit local conditions.

High resilience baseplate systems include the Delkor Egg (formerly Cologne Egg) and Pandrol VANGUARD, which can provide good acoustic performance.