**Preface to "Nondestructive Testing (NDT)"**

Because of the unavoidable aging and deterioration of materials, the efficient maintenance of civil structures and infrastructures is becoming a major issue for public and private institutions. As a matter of fact, the structural conditions of built heritage affect both safety and economic aspects. In this context, structural health monitoring (SHM) is emerging as a crucial research field, able to provide vital information regarding the damage levels of structures and materials. In particular, by exploiting the most advanced technologies and techniques, nondestructive testing (NDT) is the ideal candidate for detecting defects and structural issues, both at the laboratory and full-scale levels, in a non-invasive way. Among others, acoustic emission, vibration-based identification methods, digital image correlation, tomography techniques, sonic-ultrasonic tests, Raman and terahertz spectroscopy, electromagnetic analysis, etc., allow us to evaluate the state of damage and its evolution over time. The aim of this book is to collect the newest contributions by eminent authors in the field of NDT-SHM, both at the material and structure scale. It therefore provides novel insight at experimental and numerical levels on the application of NDT to a wide variety of materials (concrete, steel, masonry, composites, etc.) in the field of Civil Engineering and Architecture.

> **Giuseppe Lacidogna** *Editor*
