Fricker, Stephan, Dr.

ETH Zürich Dr. Stephan Fricker Lehre BAUG HIL E 23.2 Wolfgang-Pauli-Str. 15 8093 Zürich Telefon: +41 44 633 71 28 E-Mail:

Research

Site Installation and Trials of the Acoustic Monitoring System SoundPrint
(Feldversuche mit dem akustischen Überwachungssystem SoundPrint)

A continuous acoustic monitoring system has been installed on a road bridge to evaluate its diagnostic performance. Sensors, attached to the structure detect and localize acoustical waves induced by wire breaks and transferred through the structure. Since these waves distinguishable characteristic features irrelevant data can be filtered out. The analysis and interpretation are done using problem oriented software. This enables a visualization of wire breaks and their clustering and thus to evaluate the deterioration process of the bridge.
In North America SoundPrint is commercially available to monitor buildings and bridges. In particular the monitoring of monostrands in flats slab buildings is common. Experiences with monitoring of a prestressed concrete bridge were made in Great Britain.
The considered bridge in Roveredo, canton Grisons crosses the river Moesa and was built in 1952. It is one of the first prestressed concrete bridges in Switzerland and each of the two spans is 30 m long. In the longitudinal direction it is prestressed with 84 tendons; there are 21 additional 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 deterioration and wire breaks.
The continuous acoustic monitoring system is operational since June 2004. Several 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.
Due to the results of the acoustic monitoring the owner decided to examine the bridge. As a consequence of the monitoring and the further assessment the owner decided to replace the bridge in 2006. The continuous acoustic monitoring of the Ponte Moesa will be continued. More wires might break spontaneously. The replacement of the bridge provides the opportunity to inspect the bridge by intrusive methods to confirm all the detected wire breaks. Furthermore the accuracy of localization can be checked and the different influences on the localization can be evaluated.

My recent publications

• Fricker, S., (2010).
  Schallemissionsanalyse zur Erfassung von Spannstahlbrüchen bei Stahlbetonbrücken,
  IBK Bericht No. 329, ETH Zürich, Dezember 2010, pp. 157.
• Fricker, S., Vogel, T., Ungricht, H., Hunkeler, F. (2010).
  Akustische Überwachung einer stark geschädigten Spannbetonbrücke und Zustandserfassung beim Abbruch,
  Bericht 643 Eidgenössisches Department für Umwelt, Verkehr, Energie und Kommunikation (UVEK), Bundesamt für Strassen, ASTRA Bern, Juni 2010, 111 pp.
• Vogel, T., Fricker, S. (2008).
  Remote acoustic monitoring to detect breaks of prestressing wires,
  Proceedings, Information and Communication Technology (ICT) for Bridges, Buildings and Construction Practice, IABSE Conference, Helsinki, June 4-6, 2008, pp. 178-179 and CD-ROM 8 pp.
• Fricker, S., Vogel, T. (2007).
  Evaluation du procédé SoundPrint par l'ETH de Zurich,
  Proceedings, DIAGNOBETON 2007, Aix-en-Provence, 10-11 Mai 2007.
• Fricker, S., Vogel, T. (2007).
  Feldversuche mit dem akustischen Überwachungssystem SoundPrint,
  Bericht 609, Eidgenössisches Department für Umwelt, Verkehr, Energie und Kommunikation (UVEK), Bundesamt für Strassen, ASTRA Bern, Feb. 2007, 92 pp.
• Fricker, S., Vogel, T. (2007).
  Site installation and testing of a continuous acoustic monitoring,
  Journal of Construction and Building Materials, Volume 21, Issue 3, March 2007, Fracture Acoustic Emission and NDE in Concrete (KIFA-4), pp. 501-510.
• Vogel, T., Schechinger, B., Fricker, S. (2006).
  Acoustic Emission Analysis as a Monitoring Method for Prestressed Concrete Structures,
  Proceedings, EC NDT 9th European Conference on NDT, Berlin, September 25-29, 2006.
• Fricker, S., Vogel, T. (2006).
  Detecting wire breaks in a prestressed concrete road bridge with continuous acoustic monitoring,
  Proceedings, IABMAS'06, Porto, July 16-19, 2006, pp. 847-849 and CD-ROM file P_315.pdf, pp. 1-8.
• Fricker, S., Vogel, T. (2006).
  Acoustic Monitoring of Post-Tensioned Bridges,
  Proceedings, Structural Faults & Repair-2006, Edinburgh, 13-15 June 2006, p. 48 and CD-ROM file OBRI-FRI.pdf, pp. 1-8.
• Fricker, S., Vogel, T. (2006).
  Überwachung von Drahtbrüchen bei Stahlbetonbrücken,
  Proceedings, Fachtagung Bauwerksdiagnose, Praktische Anwendung Zerstörungsfreier Prüfungen, Berlin, 23.-24. Feb. 2006.
  www.ndt.net/article/bau-zfp2006/p07.pdf
• Fricker, S., Vogel, T. (2005).
  Site installation and testing of permanent acoustic monitoring,
  Proceedings, SAMCO Summer Academy 2005 on structural assessment monitoring and control, Zell am See, Sept. 05-09, 2005.
• Fricker, S., Vogel, T. (2004).
  Site installation and trials of the acoustic monitoring system SoundPrint,
  Poster, Second fib IABSE workshop Durability of post-tensioning tendons, Zurich, Oct. 11-12, 2004.

Teaching activities