1887

Abstract

This paper describes the application of geophysical tomography and scientific visualization techniques for<br>evaluating the internal condition of massive concrete structure. The resulting output is a three dimensional<br>representation of the structure showing the spatiai distribution of ultrasound data. As various aspects of ultrasound<br>data (e.g. velocity and attenuation) are related to concrete quality, the location and orientation of areas of inferior<br>material or discontinuities can be identified. In addition, specific features within the image can be highlighted and<br>quantified.<br>There are several nondestructive, noninvasive techniques for determining various in-situ properties of concrete.<br>Most of these techniques only measure properties of the concrete at, or close to, the concrete surface. However,<br>geophysical techniques such as ultrasound or seismic velocity measurements taken across a section give an<br>indication of the quality of concrete between the points of transmission and reception at the concrete surface.<br>Generally, higher velocities are indicative of good quality concrete.<br>In the current study, a large number of measurements (ultrasonic pulse velocity) are taken to provide a network of<br>velocities across a section, algebraic tomographic techniques are then applied to reconstruct a two dimensional<br>image. By taking a series of contiguous sections and stacking them together, a three dimensional model of the<br>sample or structure is created. FinaIly the three dimensional data set is visualized using advanced graphics<br>techniques such as volume rendering. Scientific visualization gives form and shape to numerical data that may be<br>abstract and difficult to interpret. Direct volume rendering in particular is appropriate for tomographic images<br>because it enhances the detailed spatial distribution of heterogeneous information without distortion or smoothing.<br>Results will be presented from a preliminary study carried out to assess the potential application of this technique<br>for evaluating the internal condition of large concrete elements. Measurements were made on a large concrete<br>block constructed with a number of internal defects such as cracks, areas of poorly compacted concrete and<br>uncemented aggregate, and large voids (polystyrene blocks). Overall, the initial results were promising, indicated<br>that the presence and location of internal defects can be determined and visualized using this technique. The<br>successful development of a technique for determining and visualizing the internal condition of large concrete<br>structures would be a significant advance in the area of concrete inspection and maintenance.

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/content/papers/10.3997/2214-4609-pdb.206.1995_006
1995-04-23
2024-03-28
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http://instance.metastore.ingenta.com/content/papers/10.3997/2214-4609-pdb.206.1995_006
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