Progress in ultrasonic tendon duct imaging

Abstract

Ultrasonic imaging of tendon ducts enables the precise localisation of grouting faults in many cases. Additionally to well known criteria for detecting grouting faults in tendon ducts new possibilities were developed recently: Phase value evaluation for qualitative distinction between steel and air reflection and analysing backscatter from the area of bottom side of tendon ducts.The application of linear array technique enables much faster data acquisition and data analyses. Examples and comparison with automated scanning measurement including phase value analysis are presented.Two main effects influence the complex behaviour of wave propagation and reflection: -Different arrangement and number of strands or internal rebars -Superposition of reflecting signals and wave modes propagation in the interface around the tendon duct. In order to understand the experimental results, EFIT modelling is performed (EFIT: Elastodynamic Finite Integration Technique). From this synthetic ultrasonic echo data are calculated. They are used as data sets for reconstruction calculation with SAFT (Synthetic Aperture Focusing Technique). These results are compared to SAFT reconstruction calculation of the measured data in order to analyse the influences of the filling condition of the duct on the propagation of the elastic waves. RésuméLa méthode d'écho ultrasonore en combinaison avec des calculs de reconstruction permet la localisation précise des inclusions d'air dans des tubes du béton précontraint. Récemment la nouvelle possibilité d'analyse de phase est appliquée. De plus, l'application d'un réseau linéaire permet de mesurer les données beaucoup plus rapidement. Des exemples sont décrits.Pour mieux comprendre les résultats et préciser les règles pour identifier des défauts, la modélisation des ondes élastiques par intégration est appliquée (EFIT: Elastodynamic Finite Integration Technique). Avec des calculs de ce type, des données ultrasonores synthétiques sont produites, servant comme base pour une reconstruction (SAFT; Synthetic Aperture Focusing Technique). La comparaison de la modélisation avec les résultats expérimentaux précise les critères pour l'évaluation d'état de l'intérieur des tubes.

Condition Assessment of Reinforced Concrete Bridges: Current Practice and Research Challenges

“…The presence of vertical cracks leads to a reduced modulus of elasticity of concrete, which can be captured using the ultrasonic surface wave method [67]. Delamination can be detected using impact echo [68,69], pulse echo [70]; and infrared thermography tests [71,72]. Table 3 The use of simple NDE tools such as chain drag and hammer sounding is the predominant practice of condition assessment of concrete bridge decks.…”

Elastic wave modes for the assessment of structural timber: ultrasonic echo for building elements and guided waves for pole and pile structures

“…In order to overcome this problem, special transducers and imaging methods based on array techniques and synthetic aperture are applied. They have originally been developed for ultrasonic 13testing of concrete elements (and are continuously improved) in research and development activities [17,18,19,5]. Some applications for timber are described in section 2.4.2.…”

Defect detection around rebars in concrete using focused ultrasound and reverse time migration

“…Successful imaging of defects, using SAFT in materials like composites and concrete through numerical simulation and experimental investigation has been reported in [11][12][13][14]. Recent developments in the field of synthetic aperture imaging of concrete involve the application of 2D arrays [15][16][17][18] which employ shear waves for interrogation of the medium. Condition monitoring of tendon ducts using shear wave transducer arrays has been reported in [16,17], wherein the SAFT generated C-scan images of the scattered field are used to identify the embedded artificial defects as steel plate or air-voids.…”

“…Recent developments in the field of synthetic aperture imaging of concrete involve the application of 2D arrays [15][16][17][18] which employ shear waves for interrogation of the medium. Condition monitoring of tendon ducts using shear wave transducer arrays has been reported in [16,17], wherein the SAFT generated C-scan images of the scattered field are used to identify the embedded artificial defects as steel plate or air-voids. It is also demonstrated that the phase information corresponding to reflected signals can be used to distinguish http://dx.doi.org/10.1016/j.ultras.2015.05.008 0041-624X/Ó 2015 Elsevier B.V. All rights reserved.…”

“…It is also demonstrated that the phase information corresponding to reflected signals can be used to distinguish http://dx.doi.org/10.1016/j.ultras.2015.05.008 0041-624X/Ó 2015 Elsevier B.V. All rights reserved. between different types of embedded objects [17]. Commercially available array systems that use the SAFT imaging modality have also been applied for monitoring the integrity of concrete pavements [19][20][21][22].…”