Demolition of the Litzbrücke, Silbertal

Published 15/11, 2017 at 18:02

Due to a structural analysis error, the Litzbrücke bridge that will connect Schruns with Bartholomaeberg in Vorarlberg, Austria, had to be demolished three months before its completion.

There was insufficient load bearing steel allowed for in the calculations and although Vorarlberg Highways Department revealed the bridge was not in danger of collapsing, it would not withstand heavy traffic. So the decision was made to completely demolish and rebuild the bridge.

The local company Bohr-Tec, a specialist in core drilling and concrete cutting work, was contracted to remove the bridge by the State of Vorarlberg. Bohr-Tec managing director Peter Gortano decided to carry out the demolition with Tyrolit machines.

About 360t of reinforced concrete had to be removed in a tight schedule of just six weeks. To meet this time frame the demolition was carried out in steps and planned in advance. The first involved separating the roadway step plate from the abutments and then removing parts of the foundations using the Tyrolit FZ-4S Hydrostress wall saw laid on the tracks. 

To achieve the necessary cutting depth of 1.5m, Bohr-Tec had to work up to it slowly and increase the size of the wall saw blades from 1.2m up to the biggest available Tyrolit of Ø 2.2m in four stages. During the cutting it was necessary to fit the largest diamond saw blade with new segments. Tyrolit's service chain made it possible for the finished tool to be ready for reuse within two hours. 

The next step was to break the bridge up into individual parts for removal, each weighing about 15t. Core drillings were made to enable the insertion of Tyrolit DWM***-C diamond wire into the holes and wound around the structure for cutting the concrete. In order to perform the wire sawing as quickly as possible three Tyrolit Hydrostress systems were used at the same time; two SB wire saws with a PPH40RR*** drive and a WCH8*** wire saw with a PPH20RR*** drive. The diamond wire ran at a speed of 23m/s and an operating pressure of 120bar through the concrete. 

In the third and last demolition phase, the 24 concrete parts, each weighing about 15t, were fixed to four attachment points and removed by crane. The construction work on the new bridge is already in full swing and was scheduled for completion in August 2017.

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