Structural Health Monitoring using innovative smart devices

Structural health monitoring is increasingly required in the field of infrastructure, both because standards expressly require it and because current guidelines for bridge maintenance and monitoring refer to it for existing works. Indeed, a perspective approach to functional materials and structures pushes toward monitoring systems effective since the construction stages and up to its end of life. Monitoring systems are divided into two main groups: those embedded into the structure and those attached superficially to the structure. The first one, being inside the structure, are better protected, but difficult to replace in case of damage; the latter are subject to external environmental aggression, but easy to replace. Currently, new structural health monitoring systems are under continuous development to detect stresses inside the structures, in order to have accurate, easy to install and low-cost tools. One of these new technologies is the "S3 System" (Tondolo, 2016), which is currently under study; it is a system embedded in the structure, which consists of a reinforcement steel bar in which a sealed cavity filled with a fluid is made. This cavity hosts a low-cost MEMS (Micro Electro-Mechanical Systems) sensor, able to measure pressure and temperature variation, with which it is possible to calculate the volume variation of the cavity itself, that is correlated to the axial deformation of the bar. Along this master’s thesis, the work carried out in previous studies (Battistoni, 2018) was continued and implemented, where the "smart" reinforcing bar instrumented with this technology was modeled with finite element software, with the aim of investigating the operation of the "S3 System" and the behavior of the integrated reinforcing bar together with the measuring instrument and the relative machining necessary for its insertion. A campaign of experimental tests was also carried out on a "smart" bar, equipped with sensors of the “S3 System”, carrying out long-term monitoring of pressure and temperature, where, through the processing of experimental data, the theoretical assumptions could be verified. From the results of this work, in the future studies may lead to a more effective design to improve the global system. Currently, there is a demand for this instrument for geotechnical works such as tunnels, but the studies have confirmed the validity of this new smart technology, which in the future could become an automatically integrated system for any type of structure.