The Peer review has evaluated this group as Average
The analysis of the signals recorded during several shaking table tests carried out in the years 1995- 98 on models of masonry buildings allowed energy absorption and dissipation during the shocks to be quantified and to be correlate with damage evolution. It was also seen that the larger the energy absorbed by damage, the more delayed are the ultimate conditions for the building. Starting from these facts, new investigations have been taken up aimed at developing appropriate devices to increase energy absorption and dissipation at the occurrence of damage while also partially controlling it. These devices are intended for both existing and new masonry buildings. Their purpose is not to increase the lateral resistance and the stiffness of masonry buildings, but to grant them higher ductility, being that quite often masonry resistance fairly satisfactory and higher than what is generally expected. The increase of energy absorption is based on the use of articulated systems with dissipative hinges made of lead. A large number (more than one hundred) of geometrical configurations of these systems and of their components have been designed, built and bench-tested by dynamically applying sinusoidal displacements of progressively increasing amplitude and measuring the relevant absorbed energy. The final devices differ in shape and size depending on the possible locations of their application: at windows, on the surfaces of walls, at the connections between orthogonal walls inside the building and externally, as tie rods (chains), to prevent wall separation. Additionally, a distributed energy absorption system consisting in a special lead network to be laid on walls and on their mutual connections has been designed and tested. In order to assess their functionality shaking table tests on significant portions of masonry buildings, scaled 1:1 and weighing about 20 tons each, have been carried out. The masonry systems were of two types, in order to catch respectively the in-plane effects of base inputs (five prototypes) and those out-of-plane (two prototypes). The energy absorption devices have been applied on these masonry systems, each subjected to a sequence of base motions of increasing severity up to near ultimate conditions. Tests on the first five systems were finished by the end of 2003 and those on the other 2 systems by the end of February 2007. Response accelerations, recorded at several locations, have been processed in order to estimate the evolution of modal parameters, of forces and lateral displacements, of stiffness and of energies with increasing damage and severity of shakings. The effects on responses due to the increased energy absorption caused by the devices were fairly positive. The lateral resistance and the lateral stiffness remained unchanged with respect to the virgin system (with no device applied) but the resistance could be maintained for lateral displacements up to four times those corresponding to the original (virgin) masonry structure. This resulted in a higher seismic severity causing ultimate conditions, of the order of 1.6 times that pertaining to virgin systems. The large amount of data collected during the 51 base motions applied to the masonry structures allows further insight into their behaviour, work which is actually being carried out. Additionally, it is to be remarked that the philosophy which the absorbing devices are based on (consisting in the capture of relative displacements between points of the structure that cause the deformation of the lead hinges and produce energy absorption) can be employed for the same purposes in modern r.c. structures, e.g. in bare frames of soft-storey structures and at the pile-slab connections in bridges. These features have not been considered to date, but are possible hints for future work. Shaking table tests were carried out by the shaking table in Seriate –BG-, formerly operated by ISMES and currently by a society belonging to the same control group (ENEL). Tests and construction of the energy absorbing devices took place at a specialized mechanical center (ATV-Varitek, 148 Colico –CO-). Funding came from the local government of Regione Umbria, for a total amount of about 550 k€.