Preliminary validation of an innovative stress sensor for the Structural Health Monitoring of masonry buildings

Structural Health Monitoring (SHM) of existing masonry constructions is a challenging topic widely studied by the scientific community. In this paper, the use of a low-cost Capacitive Stress Sensors (CSSs) is investigated as an effective tool for the detection of the compression state level in mortar joints of masonry structures. The study is conducted by means of Finite Element (FE) simulations aimed at reproducing the mechanical response of a prototype of innovative CSS, recently patented, subjected to compression forces typical of masonry buildings under serviceability conditions. The constitutive behaviour of the sensor is validated against the results of a pilot laboratory test on a mortar cylindrical specimen endowed with CSSs and LVDTs and then subjected to cyclic uniaxial compression. The FE model is built in order to simulate the capacitive sensor embedded within the mortar material; therefore, a correlation analysis is performed by comparing the numerical stress-strain output of the sensor and the experimental results. The validation procedure shows that the numerical results are in good agreement with the records obtained by the LVDTs. Moreover, the FE model is used for developing a parametric analysis aimed at highlighting the effects of mortar stiffness and strength on the efficacy of the SHM performed by the CSSs and the optimal serviceability configurations are accordingly identified.