The temporary artwork ‘La Caverne du Pont-Neuf’, a walk-in rock grotto, was created as a tribute to the legendary wrapping of the Pont-Neuf by the artist couple Christo and Jeanne-Claude in 1985. The new structure consisted of an inflatable structure approximately 120 metres long. In early June, violent gusts of wind and hail damaged parts of the outer shell. Just a few hours later, the French lifting and industrial services company Ponticelli, together with the project managers, developed a suitable lifting solution. “We were on site just a few hours after the damage occurred to work out the best technical solution together with the client,” says Louis-Arthur de Quatrebarbes, Head of the Handling/Lifting Agency at Ponticelli. “As well as repairing the tarpaulin, we had to carry out a lifting operation safely in almost constant wind and under considerable time pressure.”
A bespoke solution for the Pont-Neuf
The work took place on the oldest bridge in Paris – a listed structure with limited space and high visitor numbers. Load-distribution plates reduced ground pressure in the area of the historic bridge structure, whilst extensive safety and traffic management measures ensured the operation could be carried out safely.
Originally, a larger mobile crane had been planned. However, due to the local conditions, the Liebherr MK 88-4.1 proved to be the far more suitable solution. Its 45-metre-long trolley jib reached all the damaged areas of the structure, whilst the four-axle design enabled easy relocation from one side of the bridge to the other, where there was also storm damage. The short set-up time and compact outrigger system further facilitated the operation.
A particular advantage was the crane cab, which could be moved to working height. It provided the crane operator with an excellent view of the approximately 18-metre-high structure and the rope access technicians. The boom-mounted spotlights ensured optimal illumination of the work area during night-time operations.
Precision at night
The repair work was carried out over four night shifts. Damaged fabric sections weighing between 200 and 400 kilograms were lifted and reattached in collaboration with rope access technicians. As the construction site was located in a wind corridor along the River Seine, weather conditions were continuously monitored. Communication between the crane operator and the rope access technicians took place continuously via radio.
Before work began, site inspections, load calculations and collision analyses with the surrounding buildings were carried out. A 360-degree test subsequently confirmed the planned crane positioning.
Technology becomes part of the art
For Ponticelli, the project was far more than a conventional lifting operation. “We are proud to have been part of this work of art. To quote JR: ‘The installation of the artwork is part of the artwork’ – and so is the crane,” explains Louis-Arthur de Quatrebarbes. “The visually striking deployment of the MK crane created a magical moment.”
With its successful deployment on the Pont-Neuf, the Liebherr MK 88-4.1 mobile construction crane demonstrated its strengths in demanding inner-city projects. Where heritage conservation, confined spaces and the highest precision come together, the mobile construction crane offers the right combination of reach, compactness and flexibility.
