Soundprint was developed in Canada and is distributed in Europe by Advitam. Sensors, systematically attached to the structure register and localize energy induced by wire breaks and transferred through the structure as oscillation. Since every oscillation got a characteristic spectrum irrelevant data can be filtered out. The analysis and interpretation is done by a special software. Thus wirebreaks can be detected and subsequent wire breaks or deterioration can be controlled.
The acoustic monitoring system Soundprint will be applied to a structure under site condition and scientific attendance for the first time in Switzerland. The system will be tested and evaluated under continental European and alpine conditions.
Artificial signals with and without correlation to post-tensioning will be generated in a blind trial arrangement and the diagnostic skills of the system will be tested. Deliberately created and spontaneous occurring wire breaks are supposed to be identified by the system. Other events not evident for the structural resistance will be filtered out.
In this project will be used as a crucial method field trials.
Here is the final report of the project:
The working group Bridge Research of the Federal Highway Authority initiated to use the Ponte Moesa in Roveredo canton Grisons as a pilot project for a continuous acoustic monitoring. The Ponte Moesa was built in 1952 and is one of the first prestressed concrete bridges in Switzerland. Each of the two spans is 30 m long. In the longitudinal direction it is prestressed with 84 tendons; there are 21 additional cap-tendons above the pier. Each tendon contains 12 wires of 7 mm diameter.
Insufficient grouting and de-icing salts among other causes have led to serious deterioration and wire breaks. Due to its rather small dimension, the ambient noises from constant but manifold traffic, the ongoing deterioration process and the knowledge gained by the periodical inspections, the Ponte Moesa is an appropriate test object to install continuous acoustic monitoring.
During the monitoring period from June 2004 to May 2006 17 spontaneous wire breaks have been detected, classified and localized. Three of those were confirmed by invasive inspections. Additionally, two artificial wire breaks in fully grouted tendons were performed by catalytic corrosion cells as blind tests. The localization accuracy was satisfying. Most of the other recorded events were caused by construction activities. Irrelevant signals and ambient noises such as noises from expansion joints, bearings, traffic, construction activity and other ambient sources were also detected, classified and filtered out. As a consequence of the monitoring and the further assessment the owner decided to replace the bridge.
On the basis of the data obtained during the monitoring, it can be concluded that continuous acoustic monitoring is able to record, analyze, classify and locate wire breaks in grouted and partially grouted tendons. It is also considered capable of filtering out events that are not decisive for the structural capacity of the bridge.
The continuous acoustic monitoring provides for the maintenance of the bridge competent engineer with additional information and allows new options and financial leeway for the repair and durability of the structure.