Special Issue on Nondestructive Testing in Civil Engineering

This special issue of the Journal of Infrastructure Systems aims to provide an overview on advances of advanced nondestructive testing (NDT) applied to civil engineering structures.

Indeed, a stage has been reached in which a substantial part of the infrastructure is entering a critical age. Dams, bridges, tunnels, pavements, and nuclear power plants require sustainable maintenance to qualify for extension of their service life in good condition and safely with appropriate service level. NDT methods have their places aside more widespread visual inspections and destructive tests within this process even though few standardized procedures exist. Because of their nonintrusive nature, NDT methods will play a prominent role in the future as more and more challenges specific to civil engineering problems, such as very large investigation zones and low cost requirements, have recently started to be tackled by researchers and companies involved in this field (automation, imaging, optimized data acquisition procedures, signal processing, and miniaturization of the equipment).

Today, a wide range of NDT methods are available, including electromagnetic methods, ultrasonic methods, electrical methods, optical methods, eddy current, infrared thermography, and gammagraphy. A combination of several methods is often judicious taking into account that, on the one hand, the structures surveyed are often complex and in an open varying environment and that, on the other hand, NDT observables are usually not in direct link with engineering information needs (porosity, density, residual stress, and bounding).

NDT development is ineluctable but should rely on an improved understanding of its underlying physical principles. Also, standards, education, and training need to be addressed. Nondestructive evaluation also concerns structural health monitoring with the design of cost efficient permanent instrumentations to survey modifications over time and space, not to mention the use of NDT data as input and output controls for residual time life prediction models.

Because of previous international symposia on NDT in civil engineering, the interest in such techniques has grown, induced by an increase in their confidence, reliability, and user-friendliness. Nevertheless, some elements have to be improved, including their cost effectiveness through high acquisition rates, and the knowledge of the links between ND measurements and the durability indicators of the surveyed structures.

Thus, the following papers highlight some particular results presented during the International Symposium on NDT in Civil Engineering (NDTCE’09), coorganized in Nantes, France, by IFSTTAR (former LCPC), the Research Institute in Civil and Mechanical Engineering (UMR CNRS GeM—Nantes Univ.) and COFREND (the French Association for Nondestructive Testing).

The first paper by Kruschwitz et al. is on the application of spectral induced polarization (SIP), a well-known test method in geophysics on flooded masonry.

Gucunski et al. propose a three-dimensional approach by using the Impact-Echo technique to survey a bridge deck. The associated interpretation methodology allows both the overall assessment of the condition of the deck and the identification of deteriorated zones of the deck for repair or rehabilitation.

In the next paper, Felicetti tends to limit the destructive approach by using the analysis of cores for the assessment of deteriorated cover-concretes, although, taking into account the information from drilling monitoring. Then a small hole realized by a hammer-drilling method gives faster and reliable information of the variability of the mechanical properties versus depth.

The fourth paper (Arosio et al.) deals with radar and sonic NDT techniques used for the quality control of concrete masonries. For that, an automatic specific procedure has been designed, and it tested as well on laboratory test structures as on-site.

The last paper (Pinto et al.) is devoted to the determination of load-deflection curves of as-built drilled shafts of a case study. The testing program consisted of monitoring accelerations generated at the top of the shaft by means of a dynamic-force transducer. A numerical approach has been developed to extrapolate the load-deflection curve into the service load range, thus defining load-deflection curves.