Pervasive Structural Health Monitoring with low cost innovative sensors

SHM is a strongly developing branch of engineering that makes it possible to ensure the safety and functionality of almost all structures of civil interest. It consists of innovative monitoring techniques that involve the use of devices that once installed will accompany the structure throughout its whole service life, guaranteeing that it is continuously monitored. Keeping the structure under consideration under constant observation distinguishes SHM from traditional monitoring techniques. In recent years, research has become increasingly interested in making systems that ensure not only reliable measurements, but also practicality of installation, low cost, and small size. This thesis focuses on an innovative monitoring device called S3T (Tondolo, 2016). The latter consists of a Micro Electro-Mechanic System (MEMS) placed inside a cavity made in a common φ20 rebar. The MEMS sensor in question is an instrument capable of acquiring air pressure and temperature data, from which the tensional and deformative state that characterizes the bar can be determined. The following thesis consists of an opening chapter in which an overview of the most widespread structural monitoring systems in the civil engineering world is given. In the second chapter, after a detailed description regarding the operation of S3Ts, the studies elaborated by previous thesis writers (Battistoni, Bandinelli, and Delle Castelle) are outlined and a comparison between S3Ts and the most similar monitoring systems is carried out. Next, in Chapter 3, the results obtained from the study of sensors installed in five φ20 instrumented rebars are presented. More in detail, these were subjected to both 'long-term monitoring,' in which the rebars were maintained in a temperaturecontrolled environment, and to several tensile tests. Special attention is paid to the temperature compensation methodology, developed from measurements obtained in the thermal chamber with the aim of being able to apply it to tensile tests, but also to existing structures. It is precisely existing structures that are discussed in Chapter 4, where the study done by Delle Castelle (2022), who examined the behavior of a monitored bridge (Lemene), is continued. In this section, following the execution of a structural testing, a comparison is conducted between the results obtained from the S3Ts, installed in the top slab of the deck, and the traditional structural analysis.