Abstract. Structural Health Monitoring (SHM) of existing masonry constructions is a challenging topic widely studied by the scientific community. In this paper the use of capacitive stress sensors is investigated as 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 an innovative capacitive stress sensor, 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 laboratory tests on cylindrical specimens subjected to uniaxial compression. During the casting, capacitive stress sensors have been introduced within each mortar cylinder; the specimens have been tested under compression using a universal testing machine with displacement control and LVDTs have been placed for monitoring the local displacement and obtaining the stress-strain constitutive curve of each mortar specimen. 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 records obtained by 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 capacitive stress sensors and the optimal serviceability configurations are accordingly identified.

Keywords: Structural health monitoring; capacitive stress sensors; axially loaded cylinders; numerical modelling; experimental tests.