Papers by Author: Davide Masera

Abstract: Historical churches, masonry towers and bell towers are structures subjected to high risk, due to their age, elevation and low base area on height ratio. In this work, an innovative monitoring technique for structural integrity assessment of historical buildings is reported. At the same time, the emblematic case study of the Turin Cathedral Bell tower is presented. The damage evolution in the tall masonry structure is described by the evaluation of the cumulative number of AE and by different parameters able to predict the time dependence of damage. In particular, since environmental disturbances have been minimized, and instrumental noises have been filtered out. The b-value analysis shows a downward trend to values compatible with the growth of localized macro-cracks at the base of the tower. These results seem to be in good agreement with the numerical analysis. Extension to longer monitoring periods and, later, investigation of different segments are strongly recommended to assess the stability of the monument.

Abstract: The aim of this work is to analyse the mechanical response of the masonry specimens under long-term action by means of cyclic tests. To this end laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino. The Acoustic Emission technique was employed to assess the damage evolution, and the mechanical properties decay in order to evaluate the extent and the evolution of micro and macro-cracking due to cyclic action until structural collapse in masonry blocks and mortar layers.

Abstract: Experimental researches conducted in recent years at the Non Destructive Testing Laboratory of Politecnico di Torino have revealed an unexpected thermal response of concrete subject to short duration cyclic compressive tests: a cooling phenomenon has been observed on medium-quality concrete cores and this contradicts Kelvin’s thermodynamic laws. Such a decrease in temperature is not to be ascribed to the evaporation of absorbed water, while it depends on the applied load intensity, the application frequency and the total number of cycles performed. Moreover, the cooling phenomenon is accompanied by such mechanical effects as performance enhancement and increasing brittleness, observed through static tests performed at the end of cyclic compression: an increase in the failure strength and the elastic modulus of the material as well as a reduction in max. displacement at failure are seen to occur. The present research takes its starting point in the above observations and aims to investigate the relations between thermal and mechanical effects in concrete, in order to check the possibility to use the variation of temperature at the end of a short duration cyclic compressive test as an indicator for the evaluation of damage, the final aim being to develop in the future a methodology for diagnosis of existing structures.

Abstract: The aim of this work is to develop a procedure to follow the evolution of micro and macro-crack in unreinforced and reinforced masonry walls by means of Acoustic Emission signal analysis. In particular the main goal of this experimental work want to be the definition of a characteristic signal parameter able to represents the evolution of the fracture dimension in the masonry walls during the fracture process. To this end laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino.

Abstract: The aim of this work is to analyse the mechanical response of the masonry specimens under long-term action by means of cyclic tests. To this end laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino. The Acoustic Emission technique was employed to assess the damage evolution, and the mechanical properties decay in order to evaluate the extent and the evolution of micro and macro-cracking due to cyclic action until structural collapse in masonry blocks and mortar layers by means of a novel Acoustic Emission analysis technique.

Abstract: The aim of this work is to develop a procedure to follow the evolution of fracture in RC Beams strengthened with CFRP sheets by means of Acoustic Emission signal analysis. In particular the main goal of this experimental work wants to be the definition of a characteristic signal parameter able to represent the evolution of the fracture dimension in the RC Beams during load test. To this end, laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino.

Abstract: The paper presents the results of an experimental investigation conducted on bricks. Prism-shaped specimens were produced. Laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino. They were subjected to static compressive tests for the determination of their mechanical properties and cyclic compressive tests for the analysis of their fatigue behaviour. The aim of this work is to apply a failure criterion based on the observation of the static and cyclic curves to estimate the fatigue life and the long-term behaviour of the brick. Subsequently, it will be possible to give a relation between the static-displacement and cyclic-displacement of the material tested.

Abstract: An experimental analysis on a set of strengthened masonry walls has been carried out by means of cyclic loading tests in order to simulate the creep effects. Laboratory tests were carried out at the Non-Destructive Testing Laboratory of the Politecnico di Torino: ad hoc brickwork specimens were manufactured and reinforced by FRP and strengthening mortar. The main goal of this experimental work is to demonstrate that in the choice of the masonry reinforcement is important to value not only the increment of the ultimate strength of the material reinforced, but also its response and durability in term of long-term action, called as creep phenomenon.

Abstract: The results of an experimental study concerning the behavior of concretes made with recycled aggregates under repeated mechanical and thermal actions are presented. A comparison with the performances achieved by similar concretes made with traditional aggregates in the same working conditions eventually made it possible to estimate the actual quality and durability of the recycled concretes examined and identify possible limitations in their use. The laboratory protocol here adopted is suggested as a practical experimental procedure to test hardened concretes and pre-qualify their performances with respect to compressive actions and thermal solicitations.

Abstract: An experimental analysis on a set of strengthened masonry walls has been carried out by means of cyclic loading tests in order to simulate the creep effects. The damage evolution of specimens reinforced by traditional or innovative methods is evaluated by the Acoustic Emission (AE) technique. The AE time dependence during fracture propagation is analysed through a power law. In addition, the AE frequency analysis is used to obtain information on the criticality of the ongoing process.