The present contract is a service contract for the purpose of monitoring the potential breakage of post-stressing wires in the stretched connecting rods of bridges of the type

« Melle ».

This contract is composed of a firm tranche for the monitoring of 2 bridges for 2 years, as well as three conditional tranches concerning:

(a) the extension of the surveillance of these 2 bridges for a further period

2 years,

b) or on the supervision of 2 new bridges during these 2 additional years, by moving the initial equipment.

c) or on the extension of the surveillance of 1 of the 2 initial decks over a new period of 2 years, as well as the surveillance of 1 new bridge (by moving the equipment of the initial 2nd deck).

Monitoring shall be carried out by the acoustic emission method after installation of the appropriate measuring instruments on the bridges concerned. This method consists of detecting the noises caused by the rupture of an elementary wire of a cable.

Monitoring shall be carried out by the acoustic emission method after installation of the appropriate measuring instruments on the bridges concerned. This method consists of detecting the noises caused by the rupture of an elementary wire of a cable.

When a wire or strand breaks, it emits a shock wave that propagates into the cable and any surrounding concrete; This wave must be detected by a series of specific sensors positioned along the cable or structure containing the cables. These acoustic emission sensors must be designed in such a way that they can

detect high-frequency vibrations caused by the breakage of a wire or

strand and locate by triangulation the rupture zone.