Real-time monitoring of the Grand Palais des Beaux-Arts – Paris | France

The real time surveillance

The construction of the Grand Palais des Beaux-Arts in Paris started in 1897 and was finished for the 1901 Universal Exposition. Its 240 m long principal nave forms an imposing space covered by a large glass roof. The vaults of its North and South nave, its transverse nave (paddock), its cupola on pendentives and its dome, all made of steel, iron and glass, weigh about 8500 tons. The top of this structure reaches 45 m in height. The Grand Palais regularly hosts prestigious fairs and exhibitions in its 77 000 m² area.

In June 1993, a riveted element broke loose thirty-five meters high during an exhibition. It was therefore decided that the structure was dangerous and would be closed to the public. Structural distress was observed in the Southern part of the building and was attributed to alluvial settlement below the building. On the river Seine side of the building, the wooden piled foundations have disintegrated because of fluctuations of water-table levels. Studies determined that the settling of the southern wing was about 140 mm and the height variation of the metallic part of the structure equated to 70 mm. These values were significant enough to cause such structural damages.

Soletanche Bachy produced 8 900 m² of peripheral diaphragm wall (built inside the exposition area) and 2 000 jet grouting columns, under the real time surveillance of Sixense during 3 years of construction.

The instrumentation included:

• The automatic measurement of wall, pile and vault deformations;
• Temperature measurements to determinate the climatic effect on the observed displacements;
• A radio connection with the site PC installed in Soletanche Bachy site offices;
• In the event of breaching predefined trigger values (ranging from ±3 to± 5 mm according to different part of the building), alarm messages were sent to delegated people.

The Grand Palais is classified as an historic monument since 2000 and is visited by 2 million-people every year. Thanks to this work the structure will continue being enjoyed by many.