In-plane cyclic behaviour of thin joint masonry walls

New technologies for the construction of reinforced and unreinforced masonry buildings, based on the production of new blocks, are being employed and developed and are recognized by the modern generation of codes. In particular, a technique based on the use of clay blocks with small dimensional tolerance in unit height, i.e. machine flat bed faces, for the use with special mortars for thin layer joints, has been introduced only recently in most of the European countries. This construction technique allows simple and fast assemblage and enhances the acoustic and thermal insulation of the masonry walls. As a consequence of the introduction of this system for the construction of masonry buildings also in earthquake prone countries, it is necessary to assess its behaviour under seismic actions. In this framework, an extensive experimental program was carried out at the University of Padua, in order to characterize the mechanical behaviour of the new construction system, also under combined in-plane vertical and horizontal cyclic loading. The system was studied in comparison with other typologies of masonry walls currently adopted in the practice, characterized by different configurations of head and bed joints. The test set-up for the execution of shear compression tests was created on purpose for the research, after studying the most appropriate test configurations to reproduce the behaviour of shear walls. All the data collected from the experimental activity were used to assess some analytical models available for the prediction of the ultimate capacity of masonry walls under in-plane uniaxial compression and shear compression loading. A new formulation for the evaluation of the tensile strength of masonry was proposed and assessed against experimental data. The cyclic behaviour of the specimens was also modelled and this allowed carrying out non-linear dynamic analysis for the evaluation of the reduction of the elastic response of the masonry walls due to their hysteretic behaviour. The results obtained can be used as data-base and input for standardization purposes.