The out-of-plane collapse of the façade represents one of the major threats and the most frequent cause of damages of churches due to strong earthquakes. Due to the slenderness of the façade and the lack of adequate connections to the side walls and the wooden roof, the seismic action can trigger the overturning. A detailed assessment is therefore required to judge whether or not to intervene. This paper presents an approach for the seismic assessment of the stability of the façade, through a discrete element model based on a photographic survey, with the aim of representing the actual geometry and arrangement of the stone units and their effects on the kinematics of the overturning. The collapse mechanism is simulated with both, quasi-static pushover and dynamic pulse-based analyses and the results compared to those of conventional rigid-body kinematics. The proposed approach is then applied to seven masonry churches that suffered severe damages during the 2009 L’Aquila (Italy) earthquake and the failure mode provided by the analyses is compared to the damages caused by the earthquake. The method is able to give a reliable estimate of the expected failure mechanism, taking into account the quality of the masonry and the connections to the side walls, while also providing the seismic acceleration required to trigger the motion and the ultimate displacement beyond which collapse occurs.
Steel reinforced grout is one of the most effective mortar-based composites for the strengthening of masonry structures. Nonetheless, the deterioration of steel cords, especially when embedded in lime-based matrices, may compromise the long-term effectiveness of the strengthening systems. The use of stainless-steel may overcome this drawback, but it has received limited attention so far, since its higher cost makes it less competitive in the market. This work presents a laboratory investigation on the durability of stainless-steel reinforced grout against salt attack, which is the most severe aging condition. Tensile tests were carried out on bare textiles and composite specimens before and after aging in substitute ocean water for up to 5000 hours. Bent textiles, which are required by a number of structural applications, were aged and tested as well. Test outcomes indicate that this technology may be successfully used for the life-span strengthening of the built heritage.
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