Smart brick for post-earthquake assessment of masonry buildings

A wide part of the European built heritage consists of masonry constructions originally designed with very limited if not completely absent earthquake resisting criteria, exposing the structures to possible fragile collapse mechanisms during earthquakes. Therefore, it is evident that the evaluation of the health state of these types of buildings after a seismic event plays a fundamental role in the preservation of human life and the historical and cultural building heritage. Structural Health Monitoring (SHM) systems represent a possible solution to this problem by allowing the assessment of the structural performance of the monitored construction during its service life, even in real-time or rapidly after an earthquake, as well as enabling scheduling of maintenance and retrofitting interventions. Although the usefulness of such systems is widely recognized, their application on masonry constructions is still limited due to practical drawbacks experienced in the use of the off-the-shelf sensing technologies. Recent developments in materials engineering introduced in the field of SHM the use of smart materials obtained by doping traditional construction materials, such as cement-based ones, with conductive fillers capable of improving the electrical and sensing properties of the base matrix, giving to the composite the capability of detecting changes in its strain conditions through the output of specific electrical signals. This Ph.D. thesis extends a similar concept to masonry buildings investigating the innovative smart brick technology, which consists of clay bricks doped with suitable conductive fillers and thus capable of revealing changes in their strain conditions by leveraging on their improved piezoresistive capability, i.e. by varying their electrical outputs accordingly. The Thesis aims to promote the development of this newly conceived technology by addressing the missing/incomplete aspects in the reference literature, with the main objective of comprehensively designing, producing, and characterizing a reliable smart sensing device suitable for seismic SHM of masonry constructions. The choice of the most suitable conductive filler, the type of electrodes to be used for electrical measurements, the production process, and the sensing principle of the smart bricks are investigated. Furthermore, experiments are carried out to properly characterize the electrical, electromechanical, physical, and mechanical properties of such brick-like sensors. The Thesis also proposes two meaningful full-scale applications of the smart brick technology to demonstrate the effectiveness of the novel sensors in detecting and locating damages developed on masonry constructions, in particular, by focusing the attention on those induced by earthquake loading. Strategies for performing damage detection and localization by processing the measurements from the smart bricks are therefore proposed, while mechanical models are built to reproduce the performed experimental tests with the aim of numerically interpreting the outputs from the novel sensors physically installed within the tested specimens. The obtained results demonstrate that the proposed new formulation of smart bricks can be effectively employed for the post-earthquake assessment of masonry constructions, bringing the technology to a readiness level that is mature for field validation.