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The experimental pushover test performed on the Castel di Lama building is studied by means of a finite element procedure based on the equivalent frame model with the aim to test the ability of this widespread model to reproduce the experimental results and the collapse mechanisms. Pier and spandrel macroelements are modelled as Timoshenko beams with plastic hinges to take into account shear and bending failures. Assuming the nodes as infinitely rigid and resistant, it is possible to model them by introducing properly sized offsets at the ends of pier and spandrel macroelements. A force-based formulation is adopted for the macroelement, taking advantage of its higher performances in terms of accuracy and efficiency with respect to the classical displacement-based method, and the capability of naturally avoiding shear-locking problems. The response of the building walls, either unreinforced or reinforced, is analysed in terms of resisting forces, story displacements and damage patterns, and compared with the experimental results.

The seismic events which hit Central Italy on 24 August, October 26 and October 30 2016 have caused casualties and major damage mostly to buildings and architectural heritage of the Italian Regions of Abruzzo, Lazio, Marche and Umbria; the most deadly events occurred on August 24, 2016 and caused a total of 298 victims and about 4.600 people evacuated. The mainshock occurred at 3:36 am with epicenter close to Accumoli (Rieti province) and a magnitude Mw 6.0; the aftershock occurred at 4.33 am with epicenter close to Norcia (Perugia province) and a magnitude Mw 5.3. Most of the victims were in the areas of Amatrice (Ri), Accumoli (Ri) and Arquata del Tronto (AP). The earthquakes of October 30 didn't cause any victim but only some injured thanks to the fact that people was already evacuated and also because the Civil Protection was already present on the territory. Nevertheless, the impact of this seismic event was destructive; many small towns and villages, which have survived to the first earthquake, were heavily damaged. In the days following the earthquake of august 24 the Department of Civil Protection and RELUIS started the usability surveys by using the Aedes form (Italian acronym for "accessibility and damage during seismic emergency" [1]) which guides the inspector to rapidly assess the usability of a structure, including the description of damage and all the details of the building.

This paper proposes an innovative data-driven vulnerability model for the classification of the existing residential building stock, by clustering observational damage data gathered after the 2009 L’Aquila earthquake. The proposed model preserves the conceptual framework at the basis of the macroseismic approach, which allows for a thorough vulnerability classification of the built environment by resorting to vulnerability classes and by accounting for the uncertain association of building typologies to vulnerability classes. Novel aspects of this study are the adoption of peak ground acceleration for the ground motion characterisation, which allows for overcoming possible limitations related to the use of macroseismic intensity, and the use of unsupervised machine learning techniques for removing subjectivity in the definition of vulnerability classes. A probabilistic framework is then set up allowing for the attribution of a given building typology to multiple vulnerability classes, based on an ad- hoc strategy, involving the use of probability theory and using empirically-derived typological fragility functions as a target. The use of a detailed post-earthquake survey form also allows for an improved definition of building types representative of the Italian building stock

The destruction of Amatrice and the surrounding villages in Central Italy after the 2016 seismic sequence was so impressive that engineers, authorities and local communities started sharing the common feeling that historical stone masonry buildings were too below current safety standards. The severe damage caused by the earthquakes led to a general distrust of traditional building techniques, leading to the conclusion that there is nothing to do but demolish and rebuild, perhaps with a false antique. Is there an alternative? Is there a way to combine safety and preservation of architectural heritage? This paper aims contributing to the understanding of the seismic behaviour of stone masonry by reproducing, through simulation on a shake table, the progressive loss of compactness of a real scale rubble masonry wall up to the ruinous collapse with the separation between the two external leaves. The laboratory simulation allowed to evaluate the decrease of the fundamental frequency with increasing damage and estimate the maximum displacement profile and the amount of cracking that the wall is able to sustain before failing. Eventually, two modelling strategies based on finite and discrete element methods were proposed and applied to verify the capability of simulating the out-of-plane seismic response and the failure mechanisms of rubble masonry.

An experimental pushover was carried on two very similar unreinforced masonry constructions. These constructions were obtained from an existing two-story brickwork building, located at Castel di Lama and to be demolished due to the damage suffered during the seismic sequence that affected central Italy from August 2016 to January 2017. The central stairwell was demolished in a controlled manner and, thanks to the symmetry of the original building, two almost identical portions were delivered: one was simply repaired, by repointing the cracks caused by the earthquakes, the other was seismically strengthened using Fibre Net reinforced plaster or composite reinforced mortar. The plaster was applied on both faces of the load-bearing walls of the first level and only on the external face at the second level. Preliminary dynamic characterization tests were carried out on both constructions. Then, pushover tests were carried out until collapse on both portions, using a steel structure placed on a reinforced concrete mat supported by four piles, which allowed to apply increasing horizontal forces at the two floors. The experimental results were analysed carefully and compared with those obtained from suitable numerical models.

A significant proportion of the built heritage in historic centres is constituted by rubble stone masonry structures. Collapses by leaf separation and disaggregation observed after earthquakes highlight their dramatic vulnerability, especially under out-of-plane loads. Nevertheless, their dynamic response still needs to be fully investigated and their capacity may be overestimated by assessment approaches based on rigid-body mechanics. Effective retrofitting solutions are also needed to protect human lives and safeguard the built heritage, while ensuring the conservation of its architectural value. This paper describes the design of a shake table investigation on stone masonry walls, whose materials and arrangement reproduce those surveyed in the villages of central Italy struck by the 2016-2017 earthquake sequence. The test setup was conceived to induce out-of-plane vertical bending under earthquake base motion and investigate the dynamic response of multi-leaf rubble stone masonry and the gain in seismic capacity that can be achieved with mortar-based composite reinforcements, designed to prevent the leaf separation and disaggregation of the wall without compromising its fair face.

The 2016-2017 Central Italy seismic sequence severely affected existing unreinforced-masonry constructions in four regions. Those in Latium region proved the most prone to fragmentation because of an unfortunate combination of undressed natural stone units and very low lime content in mortar. Within the framework of a research project funded by the regional government, shake table tests are planned to investigate masonry disintegration as well as possible intervention techniques, as described in a companion paper. All specimens will have natural stone units retrieved from the debris in Collespada, a settlement of the municipality of Accumoli, one of the most affected by the seismic sequence. To push further the representativeness of the specimens with respect to field conditions, wall geometry, masonry fabric and mortar recipe are carefully designed. The wall thickness will be approximately equal to 0.5 m, close to average thickness surveyed in the area. Following the survey of several vertical sections of actual masonry walls, the specimens will present unconnected external leaves with a limited nucleus. Based on tests on mortar sampled from collapsed buildings, mortars will be prepared by a part of natural lime every nine parts of sand. Shear tests on sampled mortar delivered apparent cohesion and friction coefficient that are used as preliminary values of a finite-discrete element model, which can account for masonry fragmentation in dynamic non-linear analyses. The numerical model was tested under the envisioned sequence of records, belonging to the Amatrice station and related to the East component, approximately fault normal, of the two main seismic events, 24 August and 30 October, 2016.

Two techniques for the seismic strengthening of fair faced rubble masonry walls are proposed and tested on a shake table. The first solution entails the use of carbon fibre reinforced polymer connectors installed from outside through the natural stone units, without perforating the entire wall thickness, thus leaving the internal wall surface undisturbed. In the second solution, stainless-steel cords are embedded in repointed mortar joints of the fair face and connected, by means of stainless-steel bars, to a thermo-insulating composite reinforced mortar applied to the internal side. Shake table tests were performed under natural accelerograms on real scale multi-leaf rubble masonry walls, built with the stone units retrieved from the debris of a hamlet heavily damaged in the 2016 Central Italy earthquakes. Both strengthening solutions proved effective in enhancing the seismic capacity by preventing leaf separation and masonry disintegration, and in limiting damage development under earthquake excitation. Thanks to the compatibility with original materials and the preservation of the fair face, they are suitable for mitigating the seismic vulnerability of architectural heritage.

The paper presents an experimental study on mortar samples taken from historic and monumental buildings damaged or collapsed following the seismic events in Central Italy (2016-2017). Sixty-one samples were analysed via a set of diagnostic investigations to characterize the mortar and correlate it with the performance of the masonry. The techniques used were: X-ray diffraction, scanning electron microscopy and microanalysis, differential scanning calorimetry, calcimetry, Fourier-transform infrared spectroscopy, soluble salt analysis by conductimetry and dosage of anionic species by ion chromatography, particle-size analysis, direct shear. Microstructural characterization of the mortars revealed differences in mortar composition depending on their provenance. In particular the samples from Norcia contained large quantities of calcite while in the mortars from Pretare, dolomite was identified. In the case of Amatrice, only a few samples showed crystalline phases and compounds ascribable to binders. These results were largely confirmed by the other chemical and physical analysis performed, and mechanical tests also demonstrated low cohesion. The tests showed that in almost all the samples, poor quality mortars were used, and, in some cases, underachieving binder mortar.

Mortar quality is a fundamental parameter to take into account when studying the structural behavior of masonry, especially under seis− mic actions. Separation between the leaves of rubble masonry can occur, inducing the partial or total collapse of the construction. A good quality mortar is essential to delay/prevent the separation of leaves, but often, especially in ancient building with a cultural value, mor− tars have low binder capabilities. The paper presents an experimental investigation on mortar specimens taken from buildings of a little municipality in Marche region, Arquata del Tronto, heavily damaged by recent earthquakes in Central Italy (2016−2017). Both diagnostic techniques as X−Ray diffrac− tion, Fourier−Transform infrared spectroscopy and calcimetry, and mechanical test as compression tests were carried out in order to cor− relate the obtained values with the performance of the original masonry.