Detection of Fractures, Cracks and Corrosion Spots at the Reinforcement of Prestressed Concrete Structures Structures: Method: System: Roofs, halls, parking decks, bridges, tanks Remanent magnetism method or magnetic stray field measurement, non-destructive testing, no contact to the reinforcement is required, no interferences by layers (asphalt, coating, insulation) Suspended or supported guidance system for the measuring device measurement from the top, from beneath or from the side (girder), automotive magnet device (bridge slabs and parking decks) Power supply: Small and medium size device: standard 230 Volts and 25 Amp (e.g. halls), large measuring device: 60 kva and Isolation-monitoring (e.g. bridges) www.zfp-bauwesen.de Seite 1 von 11
1. The physical effect A reinforcing bar is initially magnetized with the methods mentioned above. A magnetized rebar (prestressed tendons immediately bonded or fully grouted sheaths) gets a comparable magnetic field of a bar magnet. Figure 1: A magnetic north pole (N) and a magnetic south pole (S) facing each other at the site of fracture closely adjacent (figure above). The test signal shows a characteristic profile (below). The inflection point of the signal curve is located between the two poles exactly at the position of the fracture (graph). At corrosion spots, cracks or fractures a magnetic north and a magnetic south pole are formed. At this point the generated stray field is recorded metrologically on the surface of the structure. The magnitude of the signal provides information about the cross section weakening of the reinforced steel. No barriers, but influencing parameters are: concrete cover (at the best up to 25 cm) arrangement of reinforcement other steel items metal sealing sheets www.zfp-bauwesen.de Seite 2 von 11
2. Magnetization The prestressed tendons are magnetized up to their remanence, to destroy their premagnetization by the terrestrial magnetic field, by lifting magnets during installation or by other magnetic fields. Due to the remanence of the magnetization the measuring data are interpreted in high quality. Hereafter applications are shown exemplarily: 2.1. Hall construction Figure 2: Roof construction of a sports hall. The roof girders are double curved hyperboloid shells in prestressed concrete. The guidance system is adapted to the structural component in order that the measuring unit can run very close at the concrete surface over the orthogonal projection of the tendons. depending on the location of the tendons to be tested the guidance system can be placed positioned on a scaffold or suspending at the ceiling or at a girder (in confined space conditions) different applications for the small measuring device are shown in the following figures: www.zfp-bauwesen.de Seite 3 von 11
Non-destructive testing of prestressed steel 2 1 3 5 4 6 Figure 3: 1. Measurement of a parabolic curved tendon from a bridge construction (from the side); 2. Measurement of a roof girder of a swimming hall (from beneath); 3. Measurement of longitudinal tendons of a parking deck (from above), 4. Measurement of bridge girders (from beneath), 5. Measurement of parabolic curved tendons of a bridge girder (from the side), 6. Measurement of a roof girder of a factory hall (from the side and from beneath) www.zfp-bauwesen.de Seite 4 von 11
Non-destructive testing of prestressed steel 2.2. Bridges Figure 4: Highway bridges in prestressed concrete. The transverse tendons, being installed in the bridge slab, are lying close to the surface and because of the use of deicing salt their risk of corrosion is high. Figure 5: For the investigation of slabs of highway bridges a large magnet (3 tons; automotive magnet device with a measuring velocity of about 400 m/h) has been developed. This large magnet device is designed for one traffic lane with a width of about 3,50 m. the measurement can be performed as well on the asphalt layer as on the beveled concrete surface of the bridge slab data logging for one traffic lane (3,0 m) a previous localization of the transverse tendons e.g. with a Radar-system is not required per day up to 1.500 m of a traffic lane can be measured the measuring software allows an initial assessment of the reinforcement condition immediately after the measurement a detailed analysis of the data is performed later by analytical evaluation www.zfp-bauwesen.de Seite 5 von 11
Image representation of a fracture situation for an immediate overview at the structure during the measurement for the owner or interested experts Figure 6: The evaluation shows directly the location of the tendons. In Figure 6 the magnetic north poles of the tendons are reproduced in white and the magnetic south poles in black. A black-to whitechangeover on the connecting line of a tendon indicates a fracture (see fracture signal ). www.zfp-bauwesen.de Seite 6 von 11
3. References [1] Hillemeier, B.: Das Erkennen von Spanndrahtbrüchen an einbetonierten Spannstählen, Vortrag Betontag 1993, Deutscher Beton-Verein e.v., Wiesbaden 1993 [2] Hillemeier. B.: Assessment of Structural Stability of Prestressed Concrete by Non-Destructive Detection of Steel Fractures, Proceedings of the International Symposium Non-Destructive Testing in Civil Engineering Vol. 1, 23-29, Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.v., Berlin 1995 [3] Scheel, H.; Hillemeier, B.: The Capacity of the Remanent Magnetism Method to Detect Fractures of Steel in Tendons Embedded in Prestressed Concrete, Proceedings of the International Symposium Non-Destructive Testing in Civil Engineering Vol. 1, 211 218, Deutsche Gesellschaft für Zerstörungsfreie Prüfung e.v., Berlin 1995 [4] Scheel, H.; Hillemeier, B.: Spannstahlbruchortung an Spannbetonbauteilen mit nachträglichem Verbund unter Ausnutzung des Remanenzmagnetismus, Dissertation TU Berlin, Berlin 1997 [5] Scheel, H.; Hillemeier, B.: Capacity of the Remanent Magnetism Method to Detect Fractures of Steel in Tendons Embedded in Prestressed Concrete, NIDT&E International, Vol. 30, No. 4, 211 216, Elsevier Science Ltd., 1997 [6] Hillemeier, B.; Scheel, H.: Magnetische Ortung von Spanndrahtbrüchen in Spannbeton, Materials and Corrosion 49, 799 804 (1998) [7] Sawade, G.: Anwendung der Methode der magnetischen Streufeldmessung zur Ortung von Spannstahlbrüchen, DGZfP-Fachtagung Bauwerksdiagnose, Berichtsband BB 66-CD, München 1999 [8] Szielasko, K.; Kloster, A.; Dobmann, G.; Scheel, H.; Hillemeier, B.: High- Speed, High-Resolution Magnetic Flux Leakage Inspection of Large Flat Surfaces, European Conference on Nondestructive Testing, Berlin 2006 [9] Hillemeier, B.; Walther, A.; Pak, C.: Fast Non-Destructive Localization of Prestressing Steel Fractures in Post-Tensioned Concrete Bridges, in 2008 Accelerated Bridge Construction Highway for Life, Conference, S. 409 410, Baltimore Maryland 2008 [10] Hillemeier, B.; Walther, A.: Schnelle und großflächige Bauzustandserfassung an Spannbetonbrücken, Estrichen und Deckensystemen, DGZfP-Fachtagung Bauwerksdiagnose, Berichtsband BB 112-CD, Berlin 2008 [11] Taffe, A.; Hillemeier, B.; Walther, A.: Condition Assessment of a 45-year old prestressed concrete bridge using NDT and verification of the results, NDE/NDT for Highway and Bridges: Structural Materials Technology (SMT), 16-20 August, New York 2010 [12] Taffe, A.; Hillemeier, B.; Walther, A.: Verifizierung moderner zerstörungsfreier Prüfverfahren an einem Abbruchbauwerk, Beton- und Stahlbetonbau 105 www.zfp-bauwesen.de Seite 7 von 11
(2010), Heft 12, S. 813 820 [13] Lawrence, J.; Pessiki, S.; Naito, C.; Hodgson, I.: Inspection Methods & Techniques to Determine Non Visible Corrosion of Prestressing Strands in Concrete Bridge Components, ATLSS Report No. 09-09, veröffentlicht in der TRID Database 2011 [14] Hillemeier, B.; Flohrer, C.; et al.: Instandsetzung und Erhaltung von Betontragwerken, Beton Kalender 2011, S. 350-351 [15] Hillemeier, B.; Taffe, A.: Aktuelle Regelwerke der Bauwerksdiagnostik, Bauphysik Kalender - Gebäudediagnostik 2012, S. 77 [16] Walther, A.; Hasenstab, A.: Zerstörungsfreie Prüfverfahren zur Bestimmung von Materialparametern im Stahl- und Spannbetonbau, Bauphysik Kalender Gebäudediagnostik 2012, S. 189-191 [17] Hillemeier, B.; Pak, C.-I: Magnetic localization of fractures of broken wires in pre-stressing cables of bridges and parking decks, 6 th International Conference on Bridge Maintenance, Safety and Management, 8. 12. July, Stresa 2012, S. 502 [18] Knapp, S.; Hillemeier, B.: Application of line scanner in remanent and active field compared with the big magnet impulse magnetization, 6 th International Conference on Bridge Maintenance, Safety and Management, 8. 12. July, Stresa 2012, S. 503 www.zfp-bauwesen.de Seite 8 von 11
4. Performed objects Bridges: 2002 Fuldatal Brücke; Hessische Straßen- und Verkehrsverwaltung (HSVV) 2003 Spandauer Damm Brücke, Berlin; Senatsverwaltung für Stadtentwicklung Berlin 2004 Autobahnbrücke Bismarckstraße, Leverkusen 2006 Mörschbrücke, Berlin; Senatsverwaltung für Stadtentwicklung Berlin 2007 Elsenbrücke, Berlin; Senatsverwaltung für Stadtentwicklung Berlin 2007 Lahntalbrücke, Wetzlar Ost; Hessische Straßen- und Verkehrsverwaltung (HSVV) 2008 Husberg Brücke, Werdohl; Stadtverwaltung Werdohl 2008 Spandauer Damm Brücke, Berlin; BASt, Bergisch Gladbach 2008 Fußgängerbrücke KaDeWe, Berlin; Karstadt AG Champlain Bridge, Montreal Kanada; Vector Corrosion Technology 2010 2010 Hannoversche Brücke und Hohenfelder Brücke, Hamburg; Landesbetrieb Straßen, Brücken und Gewässer Hamburg Talbrücke Uttrichshausen BAB A 7, Fulda; Hochtief Construction Materials AG Talbrücken Lützelbach und Marbach, BAB A 45; Hochtief Construction Materials AG Talbrücke Uttrichshausen BAB A 7, Fulda; Hochtief Construction Materials AG Jubilee Overpass (Straßenbrücke), Winnipeg Kanada; Vector Corrosion Technology 2011 Talbrücke Dorlar BAB A 45, Wetzlar; Hochtief Construction Materials AG 2011 2012 2012 2012 Taubertalbrücke BAB A 81, Tauberbischofsheim; Leonhard Weiss GmbH & Co. KG Autobahnbrücke BAB A 81 Würzburg Stuttgart, Abschnitt AS 4 Ahorn AS 5 Boxberg; Englert Ingenieurbüro Straßenbrücke auf der Bundesstraße 6, Hildesheim; Hochtief Construction Materials AG Taubertalbrücke BAB A 81, Tauberbischofsheim; Leonhard Weiss GmbH & Co. KG 2012 Talbachtalbrücke BAB A 81, Engen; Bilfinger Berger SE 2013 Kochertalbrücke BAB A 6, Geislingen, Leonhard Weiss GmbH & Co. KG www.zfp-bauwesen.de Seite 9 von 11
2013 Aichtalbrücke B 312, Neckartailfingen, EUROVIA Beton GmbH 2014 Hanns-Martin-Schleyer-Brücke, Esslingen bei Stuttgart, Leonhardt, Andrä und Partner (LAP) 2014 Kochertalbrücke BAB A 6, Geislingen, Leonhard Weiss GmbH & Co. KG Buildings: 1998 bis 2005 in zeitlichen Intervallen Untersuchungen von Dachbindern in Traunreut (Oberbayern) BSH GmbH 2001 Hallendachträger der Privatkäserei Bergader, Waging 2003 Untersuchungen Sicherheitsumschließung, KKW Gundremmingen 2004 Henry Ford Bau, FU Berlin; GSE Ingenieurgesellschaft mbh Saar, Enseleit und Partner 2005 VT-Falten, OKZ Berlin-Mahrzahn; Land Berlin 2007 Spannbetonfertigteilbinder Stadtbad Rheydt, Mönchengladbach; NVV AG 2007 VT-Falten, Grundschule Berlin-Mitte; Leonhardt, Andrä und Partner (Zweigstelle Berlin) 2007 Spannbetonfertigteilbinder, Renolit Werke, Worms; Renolit AG 2008 Spannbetonfertigteilbinder, Parkhaus Bahnhof Neumünster; Dywidag AG 2008 seit Spannbetonfertigteilbinder, Freizeitbad Panoramablick Eschenburg; Hochtief Construction Materials AG Tankbehälteruntersuchung, Cunnersdorf, Thüringen und Medewitz; TA- BEG Tanklagerbetriebsgesellschaft mbh Parking Garage Monongahels Valley Hospital, USA; Vector Corrosion Technology Parking Garage Foxhall Square, Washington D.C. - USA; Vector Corrosion Technology Parking Garage Dixi Road, Delta Hotel, Toronto Kanada; Vector Corrosion Technology 2010 Spannbetondachträger, Stadtbad Rheydt, Mönchengladbach; NVV AG 2011 Spannbeton HP-Schalen, Mehrzweckhalle München-Neuried; Schießl, Gehlen, Sodeikat GmbH www.zfp-bauwesen.de Seite 10 von 11
2011 Spannbetondachträger, Stadtbad Rheydt, Mönchengladbach; NVV AG 2012 Hallendachträger, Klärwerk Münchehofe; BARG Baustofflabor GmbH & Co. KG 2012 Hallendachträger der Privatkäserei Bergader; Waging 2013 Tunneldeckenträger im Altstadtringtunnel München, Baureferat München www.zfp-bauwesen.de Seite 11 von 11