Twenty strand jacks raise 6,200-tonne Austrian viaduct by 5.8 m

The commission

The Italian heavy lift contractor was engaged as a subcontractor by ICM Construction GmbH for the lift, which took place on the A10 motorway near Spittal an der Drau in Carinthia. Fagioli’s scope included the design of the lifting structures as well as the execution of the lift itself.

How the load was picked up

The arrangement placed one portal on each of eight pier heads and one tower on each of the two abutments. Every portal carried two 600-tonne strand jacks and every tower two 450-tonne strand jacks, giving twenty jacking points in total and a nominal installed capacity comfortably above the 6,200-tonne deck weight.

Spreading the load across ten supports keeps the bending demand on the existing steel deck close to what it sees in service. The trade-off is control: with twenty jacks operating simultaneously over 650 metres, the synchronisation system has to hold all points within a tight tolerance for the full 5.8 metres of travel, otherwise differential movement introduces forces the deck was never designed for.

The portals themselves are a significant piece of temporary works. Each has to straddle an existing pier head, transfer up to 1,200 tonnes of strand jack load into a structure originally sized for a different load path, and provide a stable platform for the jacks while the deck is off its bearings. The design of those structures formed part of Fagioli’s scope alongside the lifting operation.

Why lift it at all

Raising an existing motorway viaduct rather than demolishing it is a way of keeping traffic flowing while a replacement structure is built. The lifted deck can be held in position and used as a working platform above the new works, which is what makes schemes of this type attractive to road authorities on busy alpine corridors where diversions are limited.

Fagioli attributed the design of the lifting arrangement to its own engineering experience on comparable structures, and the operation was carried out with the motorway in service.

Fagioli has published a video account of the project, in Italian, at this link.

Source: Fagioli — Photos: Fagioli