Moving a structure demands absolute control over the stresses induced in the structure from the start to the end of the operation. Freyssinet and Hebetec Engineering have therefore developed a range of specific lifting equipment, with real-time control and precision enabling the most stringent requirements to be met in terms of managing reactions and movements at the jacking points. Strand lifting can be used to lift or lower almost any load, regardless of its height. It is a modular system that consists of setting up a jack and a lifting cable at as many points as necessary. All of the jacks are then operated and monitored simultaneously. Each cable is made up of a bundle of parallel high-strength steel strands, varying in number in line with the lifting capacity sought. A bundle may comprise a maximum of 55 strands and its maximum working load is calculated with a safety factor of 2.5. Cables of different sizes will often be used for a single lifting operation, allowing for the differences in stiffness of each cable.
The bundle of strands passes through the hollow jack, which is anchored at two different levels. During lifting, the two anchors are placed under load one after the other: when the jack extends only the upper anchor is locked, pulling the cable, and when it retracts only the lower anchor is locked, holding the load. This robust equipment has proven its durability and reliability during operations conducted in the course of numerous projects.