- Building Type : High office tower > 28m
- Construction Year : 1970
- Delivery year : 2022
- Address 1 - street : 18-19 Pl. des Reflets 92400 COURBEVOIE, France
- Climate zone : [Cfb] Marine Mild Winter, warm summer, no dry season.
- Net Floor Area : 38 950 m2
- Construction/refurbishment cost : 99 984 650 €
- Cost/m2 : 2567 €/m2
Primary energy need :
(Calculation method : RT existant )
Built in 1970, the Aurore tower is one of the first towers built in La Défense. Abandoned for years, a time destined for demolition, Aurore was finally heavily restructured for a new life :
- A 6-level rise increased the number of superstructure floors from 27 to 33 levels
- The 5 levels of infrastructure and the hall level have been radically redesigned (change of destination, modification of the stairs, etc.)
- The interior of the central core has also been completely redesigned to adapt to changes in elevators, technical trades and new ways of occupying offices.
Aging in the 90s, Aurore was emptied in 1998 to be asbestos removed, its abandonment lasted 10 years. The works permit for the demolition of Aurore and the construction of a new 202metres tower, Air2 is deposited and a demolition permit is displayed on the entrance door of Aurore. The economic crisis of 2008 and the appeals of the residents, will mark in 2017 the abandonment of this demolition / reconstruction, and the entry of a new investor for the realization of a new project more respectful of the existing tower.
See more details about this projecthttps://www.viguier.com/fr/projets/tour-aurore-courbevoie
©Aermont Viguier / Sisto Studio / Guillaume Maucuit or ©setec tpi
ContractorSNC AER 2
Assistance to the Contracting AuthorityORFEO DEVELOPPEMENT Morgane Koenig
Assistance to the Contracting AuthorityG-ON (étude carbone)
DesignerAgence Viguier Laure Barthelot, Thomas Poletti
Construction ManagerArtelia Bâtiment Ile-de-France
Structures calculistsetec tpi François Lebrun
Other consultancy agencyAtys Engineering
Other consultancy agencyBollinger Grohmann
OthersSOCOTEC (Bureau de contrôle)
OthersPetit (groupe Vinci)
- 74,38 kWhep/m2.an
- 149,68 kWhep/m2.an
- 157,59 kWhep/m2.an
Construction and exploitation costs
- 99 984 650 €
The Aurore complex is located in the town of Courbevoie, west of Paris, in the Hauts-de-Seine department, in the Gambetta district. It takes place in a dense urban fabric, made up of towers, on the edge of the slab, and adjoins the city of Courbevoie and the circular boulevard. The set proposes a complete redevelopment of the site thanks to its new influence and the deconstruction of slabs and buildings in its immediate environment. Thus, it frees up public spaces at the foot of the Tower, at the level of the slab of La Défense and Courbevoie. It actively participates in the opening up of commercial sectors in the immediate vicinity through the removal of portions of slabs. It promotes access from the circular boulevard, which will benefit the whole district, simplifying its service. And finally, the stairs built around the project reconnect the city of Courbevoie and the different pedestrian levels of La Défense.
Reuse : same function or different function
- Structural works
- Demolition of the structure and disposal or recycling of materials;
- Construction of a new structure.
Reproductibility and Innovation
- Understand, on the basis of archive plans alone, how the original engineer designed the tower in 1970, to fully understand the structural functioning of the initial tower, an essential prerequisite for the restructuring project; a precise calculation model of the existing tower was thus produced, and its results compared with in-situ measurements (for example, comparison of the settlements of the ground under the tower in the model with the settlements actually observed on site)
- Next, imagine the maximum elevation allowing the height of the tower to be increased (and therefore its weight and its wind resistance) without having to reinforce the load-bearing elements, and by only slightly reinforcing the slab, without the need for additional foundations; here too, a complex calculation model, integrating the construction phases (1970 / 2020) and the ground under the tower, was carried out
- Real qualities of the concrete put in place in 1970: thus, all the load-bearing elements (posts, walls) were sampled at a rate of 1 floor out of 2, and the calculation models updated as measurement of the receipt of the results of these samples
- Real qualities of the steels used
- Perfect correspondence between construction plans from 1970 (reinforcement, formwork) and on-site measurements (radars, ferroscans, surveyors)
Reasons for participating in the competition(s)
We draw attention to two subjects:
The hierarchy of waste treatment methods indicates as a priority: prevention of waste generation, then preparation for reuse, then recycling and disposal. The strategy developed for the rehabilitation of the Aurore tower allows significant waste avoidance. The implementation of a structural diagnosis and high-tech strategies made it possible to overcome the obstacles which, for the majority of the works, would have led to demolition. The conservation objective having been achieved, thousands of tons of rubble were avoided thanks to the non-demolition as well as the pouring of a large quantity of concrete for the construction of a new tower.
The rehabilitation of the Aurore tower offers another reading of the circular economy and reversibility. Reversibility is materialized here by the maintenance of existing structures which are doomed, without technical expertise, to demolition. The preservation of existing structures and the material that composes them sometimes requires high technicality to ensure the durability and safety of the structures, and thus extend their lifespan.
To extend the life of a structure, the auscultation and diagnostic phase made it possible to measure the state of the existing structure, and to identify the margin of action in order to take advantage of it during the elevation project. This phase must make it possible to issue an opinion on the quality of the initial design, to characterize the materials used, as well as to retrace the maintenance and operation of the structure during its first life cycle. This is an essential step to ensure the conformity of the existing structure and authorize the elevation. The very good knowledge of the existing (plans found, numerous reconnaissance campaigns) and the good condition of the structure were decisive.
From the outset, the renovation project was imagined by all its designers to be as virtuous as possible in environmental terms. The desire to minimize the reinforcement of the existing structure led to a design of the elevation by means of a mixed light structure compatible with the IGH constraints (steel/concrete with collaborating floor). The number of floors added has been adjusted according to the capacity of the existing structures and by limiting the reinforcements to the raft.
In response to the in-depth diagnosis carried out, the rehabilitation project for the existing structure is carried out by choosing an appropriate solution. The increase in stresses by adding additional floors requires reflection on the exact need: by raising what is necessary and what can be compared to the existing one so as not to generate renovation work. too much reinforcement. The reinforcement solution must be reasonably established so as not to have a high environmental cost in relation to what is preserved. This is why the elevation was limited to 6 floors.
In the same way, the pavilion was designed to respect the existing structures of the car park as much as possible and to avoid inappropriate reinforcement.