Located on the A16 highway next to Boulogne-sur-Mer in the Pas-de-Calais , the Echinghen Viaduct (1997) is a bridge with hollow-core concrete segments with steel cantilever frames.
With a length of 1,301m, the main span is 110m long and the height of the concrete segments varies from 5.5m in the vault and 8.00m in the supports. They lay on high pylons.
The prestressing system is not embedded in the concrete but within the hollows, injected in mortar inside PEHD made ducts.
Some assessments of the damaged ducts were undertaken in the Echinghen Viaduct in October 2017.
These damages were found in the connection areas of the ducts. The assessment confirmed that there was a serious problem of corrosion inside the ducts affecting critical zones, with a dissolution of the constituent steel element (FE203). As a result, some of the cables were broken and the tensile section reduced.
A significant renovation operation was launched by the SANEF between the end of 2017 and the start of 2018 to assess the 331 steel cables within the structure and ultimately replace them.
The calculations executed following this model helped with the verification of the stresses in the different section elements for each of the 19 scenarios of the replacement of the cables.
