Stability calculation of the CNIT

by J.-P. Deveaud, Cerema*, member of Code_Aster ProNet

As part of the extension of the line E (Eole) of the Paris suburban rail network to La Defense, it is planned to build a new station under the CNIT building (Centre of New Industries and Technologies). LCPC expert and Setra* were entrusted with the stability analysis of this structure when submitted to potential movements induced by the construction work.

The building consists of a freestanding arch made of reinforced concrete, which is 22500 square meters wide and only six centimeters thick, and whose span reaches 218 meters constituting a world record. This arch is supported by three 84 tons concrete abutments which are connected by 44 steel wires.

Figure 1 : Postal card of the CNIT building in the seventies	Figure 2 : CNIT in 2005, the pedestrian slab covers about a third of the height (© David Monniaux / Wikimedia Commons, CC-by-3.0)

The Setra generated a finite element model of the CNIT structure with Code_Aster to assess its sensitivity to any displacement which may occur during construction.

Figure 3 : Geometry of the structure	Figure 4 : Vizualisation of stresses under own weight

Shell surface elements (COQUE_3D) were used to model thin parts of the structure such as the upper and lower shells of the vault while volume elements model the large parts such as the abutments. An elastic linear calculation was carried out. The model features 74694 elements and 215360 nodes.

Figure 5 : Vizualisation of stresses under uniform temperature variation in the upper shell and the lower shell

* On January 1st 2014, the eight CETE, Certu, Cetmef and Setra merge to give birth to Cerema : Centre of studies and expertise on risk, the environment, mobility and development