Assessment and non-destructive testing in civil engineering

The introduction of NDT and NDT in civil engineering, and even their development, requires us to first outline their definition and use. In most cases, they are measurement or control tools or methods capable of providing access to one or more physical, physico-chemical or chemical quantities characterizing the phenomenon under study, by obtaining either quantitative values, or information by thresholding values in the case of event detection. Today, the notion of instrumentation is no longer limited to "the instrument", but includes the sensor or sensor network, and the capture, transmission and processing of information. It also encompasses the action that leads to this system or means, and the intellectual and practical approach that presides over this action. It is necessary to design methods, to imagine means, to invent investigation tools to characterize the state of the system, to act on it, to understand how it works, to feed behavior models. This requires a global approach to the system, taking into account cognitive thinking and measurement or investigation tools. In this context, the physics of the wave and its interaction with the structure must be mastered, as must the generation of this wave and the interpretation of what is measured. In addition, direct or inverse modeling and a multi-scale approach are needed to better design the generation equipment, optimizing the process with respect to the structure under study, and to derive maximum quantitative information from the observations, or even to aid decision-making.

Depending on the levels of knowledge, learning and automation imparted to the system, we then cover the field commonly referred to as "intelligent systems" or "smart systems". In practice, instrumentation can be used for a variety of purposes, including :

• as a means of detecting and monitoring pathological conditions (deterioration, deformation, cracking, etc.) in materials and/or structures;

• as permanent, real-time or near-real-time tools for monitoring the health of structures and assisting in their maintenance;

• as an essential link in a servo chain, for active or semi-active control of a structure;

• as a tool for recording or characterizing a condition, behavior or level of service.

The civil engineering sector is very receptive to all the means available to help optimize the construction phase and its subsequent monitoring, check compliance with current standards or ensure short-, medium- and long-term maintenance of structures, and is now making routine and targeted use of modern operational techniques. By way of illustration, some NDT techniques, such as RADAR, ultrasound,...