The PB12 Tower built during the early 1970s (the former Crédit Lyonnais Tower) is in la Défense between the Atlantique Tower and the Ariane Tower in the proximity of the La Défense Square.
It has 8 infrastructure levels and 27 floors, each 3.11m high, for a total height of 90m with respect to the La Défense Sq.
The tower’s restructuring consisted mainly of:
- the replacement of the existing façade posts (distanced every 1.5m) by composite steel/concrete (distanced every 6m), therefore elimination of 75% of them
- the widening of the tower’s East façade by 3m
- the creation of a new reception hall along with lightwells between
The operation also included the rehabilitation of the two 6-storey volumes located East and West of the Tower and the creation of 5 parking levels under the building.
The central core was preserved and extended both in the infrastructure and superstructure. The superstructure slabs were preserved except in the peripheral area where a new metallic structure was installed as support due to the removal of the existing posts. The infrastructure slabs were either preserved or not depending on their suitability for the project.
Production of execution drawings of the structure rehabilitation’s design project (450 drawings)
The significant vertical loads already applied to the existing structure, the increased dimensions of the tower and the application of new regulations (augmented wind pressure) led to a reinforcement of the core with additional retaining walls and carbon fibres.
The calculations were carried out using a finite elements model considering the special features of these additional walls (incidence of phasing, retraction stress forces) in order to verify the performance of both the existing and the additional walls.
The structure’s core had to be verified considering the new openings, the existing reinforcement and the concrete’s resistance measured in-situ. The new composite posts were sized considering the differential settlement compared to the core.
Client : SCI PB12 (AXA)
Delegated owner : COGEDIM
- Architecte : VALODE et PISTRE
- BET Structure : setec
- BET Fluides : OTH
Period : 2002 – 2004