Resilient Baseplate

The rail is attached to a concrete slab or plinth by means of a baseplate assembly containing resilient pads.

Direct fixing to plinth has been used throughout the world as a system with reduced dead weight for bridges and viaducts. Examples of this track type can be seen on Hong Kong MRT, Docklands Light Rail and Kuala Lumpur Star LRT. Where a high percentage of the route is on structure, the reduction in dead weight of the track construction becomes a high priority.

The system is compatible with turnouts and crossovers as well as plain line.

System Components

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).

Construction

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.

Acoustic Performance

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.