A versatile 115,000 m² facility, Paris La Défense Arena is one of the two largest indoor performance venues in Europe. The Arena can be configured as a rugby stadium or a theatre and can accommodate up to 40,000 people. In the spring of 2016, Freyssinet was commissioned to carry out a difficult and meticulous operation: the lifting of the 1,700-tonne roof to the top of the structure.

  • Owner
    Racing Arena
  • General contractor
    VINCI Construction France
  • Delivery date
    September 2017
  • Partners
    Main contractor: Structures IDF
    Architect: Christian de Portzamparc

La Défense Arena - roof lifting

Initially designed with a retractable roof, the venue was ultimately built with a fixed structure. Consisting of steel mesh elements, the roof structure was prefabricated on the ground to meet delivery deadlines.

  • 1,700t
    Weight of the roof structure (tons)
  • 15ml
    Accuracy required at the top (millimetres)
  • 12h
    Duration of the jacking operation (hours)
  • 7.5
    Safety factor on the lifting cables
Advanced technical skills

Advanced technical skills

Although the initial task was to provide technical assistance for the design of the lifting systems and the construction of the temporary project parts for the operation, the complexity of the project and the technical skills required to carry it out led the constructor to broaden our scope of work: we were entrusted with all of the studies of the temporary structures required to execute the lifting, with the management of the operation itself, and with the connection of the roof structure to the peripheral part of the facility, in such a way as to maintain the correct preloading force for the central section.

An exceptional mobilisation of resources

More than 400 hours of study were needed to set up the operation within a limited timeframe (twelve months) and to undertake the preliminary work of gathering the equipment and building specific parts. The objective was to move forward quickly to meet the short deadlines, in particular by relying as much as possible on existing equipment in order to save time on calculation and procurement. Our teams carried out the sizing of the project, the general drawings of the lifting structure as well as the detailed manufacturing drawings of the temporary metal parts. These were manufactured in advance in the workshop, either by the main contractor or by using existing elements from our in-house equipment for the most complex parts, such as the 7-metre long girders that make up the lifting gantries, or the control centre.

La Défense Arena - mobilisation of resources
La Défense Arena - Faultless securing of the operation

Faultless securing of the operation

At the same time, 12 H400 strand jacks were required to ensure safe lifting: with a capacity of 400 tonnes each, the jacks could lift three times the weight of the structure. They were equipped with 37-strand, 80-metre cables with a capacity of 1,000 tonnes at break (i.e. a coefficient of 2.5 in relation to the jack). The lifting capacity of the assembly therefore exceeded the weight of the roof by 7.5 times, ensuring a maximum safety factor.

In preparation for the D day, the gantry – a temporary lifting structure – was prefabricated on the ground and then lifted and placed over the peripheral part. The jacks, previously fitted with cables, were installed with a crane at a height of about 40 metres. Each cable was then attached to a temporary anchor block underneath the structure to knot the lift with wedges (passive anchor), while on top, the anchor was activated with the jack lift.

Key figures

Jacking operation

The jacking operation took place over a dozen hours. It was preceded by a lifting test at night, during which the structure was lifted by about 50 cm to check the forces by lifting point and the good behaviour of the roof.

To prevent the strands from being crushed, twelve employees based on the gantry monitored each jack stroke, and an operator manually controlled each of the jacks. The lifting system integrated two types of simultaneous controls with vigilance threshold values and stop values. First, the pressure of each jack was monitored in real time to measure the load on each of the twelve lifting points. These had to progress evenly to avoid parasitic loads in the anchors. Then, laser telemetry sights were also attached to each fastening point on the structure, pointing to the ground to check the synchronisation of the lift between the 12 points on the structure.

At the end of the operation, when the twelve anchor points were perfectly aligned – a precision of 15 millimetres was required – the connections of the structure were installed before the final loading of the roof.

  • 35m
    Lifting height of the structure (metres)
  • 28cm
    Height of a jack stroke (centimetres)
  • 140
    Number of piston opening/closing operations
  • 20
    Team members mobilized to hoist the structure

The uniformity of the lift at the twelve points was a major concern, as the 1,700 tonnes of the roof could cause the cables to stretch by more than ten centimetres depending on the load level at each point and the risk of parasitic effects on the structure’s balance. To guarantee the same load lowering, it was necessary to adapt the number of strands per jack to the expected load and to  inject the same volume of oil into each jack, which we managed to do thanks to an iso-flow system consisting of three pumps, each feeding four jacks.

Amine  
Head of Methods Division | Technical Operations Department | Freyssinet France

Roof lifting phasing plan

Phase 1: cutting of the beam’s lifting points
Phase 2: installation et fixing of the beam n°1
Phase 3: preparation of the beam end and its anchorage point
Phases 4 & 5: installation of the lifting cable and execution of the operation
Phase 6: end of the lifting operation
Phases 7 & 8: installation of the wedges for the pushing jacks and assembly of the roof axis
Phases 9 & 10: disassembly of the cable, lifting jack and lifting beam, and assembly of the roof axis wedge

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