Wall restoration with challenging logistics
Scene: Ehrenbreitstein Fortress, Koblenz, 1,000 years of history, a Prussian fortress in the 19th century but soon to hoist foreign flags – the French till 1929 and then the American, a victorious power, after the 2nd World War.
Fortresses are per definition theatres of war and inseparably associated with hostility. Yet in a united Europe, the second largest fortress in Europe has long ceased to have any military significance, but is instead a location for peaceful, informative offers such as museums, a youth hostel, cultural centres, restaurants, event venues, etc. Every euro spent in this way represents a far better investment. And talking of investment, the owner of the fortress – the state of Rhineland Palatinate under the auspices of the Koblenz branch of the Landesbetriebs für Liegenschafts- und Baubetreuung – had to really dip into their pockets for the restoration work.
The retaining wall on the southern upper plateau had to undergo immense restoration work. Such retaining walls, which support the ground lying behind and thereby the plateau, had been subjected to extreme exposure over the centuries. The walls and the joints had suffered accordingly. The south wall scaffolding erected by the Schmöllner scaffolding company BSB Bau- und Spezialgerüstbau GmbH was positioned on a steep drop with an incredible 1 in 10 slope some 70 metres above the Rhine. When assembling the scaffolding, it was just as delicate in terms of balance and planning as it was when the walls and fortress were first built.
The retaining wall varied in its height between 2 and 15 m and was subjected to drilling, pressing and masonry works from a working and protective scaffold. And a mechanical grouting machine was also essential for this “anti-aging course of treatment”.
BSB needed six staff on average to scaffold the south wall and the rotunda within the scheduled assembly period of five weeks. To enable this, specific logistical planning was required as the time window for bringing material to the site closed each day at 10.00. After that, visitors to the fortress once again took precedence. Although the 12 tonne truck could access the square in front of the youth hostel and be unloaded there with a Merlos telescopic handler, that was it in terms of any technical assistance. Transport from there to the actual site had to be done manually.
The solution to this enormous scaffolding challenge and the overall planning were effected in cooperation with the architecture firm Barthel & Maus together with the Schalksmühle-based IBS Ingenieur- und Sachverständigen-Büro für den Gerüstbau Joachim Specht. Loads are always a problem with old walls. The support loads for the scaffolding had to be diverted directly into the wall to ensure that the earth pressure, already acting on the retaining wall, was not increased thereby encumbering it even more. Moreover, the wall surfaces had to remain absolutely accessible to enable work to be carried out on them. One of the tender preconditions was the use of the modular scaffolding VARIANT from the manufacturer scafom-rux. The system features high flexibility with regard to adapting to the structure to be scaffolded and 1,325 m² were used on the retaining wall. The structure was designed as a suspended scaffold with inner brackets, braced and supported with 405 metres of lattice girders. The challenge of anchoring to a rotten wall structure could be overcome in a different manner after consultation with the structural engineer.
BSB Bau- und Spezialgerüstbau is well-known for having implemented numerous special scaffolding structures and for the great professionalism prevailing throughout the company. To ensure that the Schmöllner-based company under its managing director Dipl.-Ing. Wolfgang Kaiser continues to live up to this claim, the veterans of the scaffolding projects Theatinerkirche Munich, Völkerschlachtsdenkmal Leipzig and even Neuschwanstein Castle were given the task of introducing and training a new generation of scaffolders to/on the flexibility benefits of the scafom-rux system. The Ehrenbreitstein project with its many rock ledges, corners and edges was simply ideal for training purposes. The 80-person strong company is specialised in handling tricky assignments and is occasionally operational far outside Germany. In this respect, industrial plant, high-rise buildings and weather protection solutions are just as much a part of the portfolio as are large-sized bridgings and other special scaffolds.
This project was – as always – carried out by BSB punctually, even though a small detail did cause some delay. The scaffolding team had to postpone the start of their work by two weeks to allow an eagle owl the necessary time to hatch out its eggs. The fitting of a temporary screen was adequate enough for the neighbourhood kestrel to enable the young kestrel to grow up in a somewhat calmer environment.