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This work presents the simulations of the non-linear dynamic response of a three-dimensional finite-discrete element model. The model simulates a half-scale masonry building aggregate tested on a shake table by other Authors. The aggregate is made of two un-connected building units having different heights and slightly different wall thicknesses. The floors are made of timber beams and boards. The modelling approach accounts jointly for in-plane and out-of-plane responses, which can be expected given the high flexibility of the floors, and for the separation between the two building units. The simulations are related both to the blind predictions, according to a scheduled testing sequence, and to the post-dictions according to the actual testing sequence and some model calibrations. The prediction model overestimates displacements, underestimates base shear and fairly predicts the damage pattern of comparable experimental runs. The use of the recorded shake table motion improves the accuracy of the post-diction simulations, while still delivering beam unseating. A higher Young's modulus of the blocks improves markedly the predictions. The strengthening intervention with steel angles connecting floors to walls is only approximately modelled and does not improve the outcomes of the simulations. In summary, the adopted modelling approach is capable of accounting for the pounding between the two building units, predicting the most significant damage as well as estimating approximate average of peak values of base shear and displacements, while individual time histories are less accurately estimated. [ABSTRACT FROM AUTHOR]

The seismic sequence which started on August 24th, 2016, caused hundreds of casualties, damage and collapses in four regions of Central Italy (Lazio, Umbria, Abruzzo and Marche). The strongest event, which occurred on October 30th (Mw 6.5), was forerun by four earthquakes with magnitude between 5.4 and 6.0. So far, a total of nine events with magnitude greater than or equal to 5.0 have taken place in the affected area. The earthquakes were caused by normal faults, all of them having NW–SE or NNW–SSE strike, approximately along the spine of the Apennine Mountains. The hypocentres of the events were at a shallow depth, between 8 and 10 km. The building stock in the affected area is mainly characterised by unreinforced masonry and reinforced concrete ordinary buildings, churches and historical constructions. Different municipalities, severely damaged, were not classified as seismic prone until 1981, or were originally attributed to a seismic zone with lower seismicity compared to the current one. This circumstance can explain, to a certain extent, the observed seismic response. In this study, aimed at interpreting the observed damage, the assessment of the damage potential of the ground motions recorded during the strongest events is performed by means of conventional and unconventional parameters. Specifically, elastic spectral demands, in terms of pseudo-accelerations, energies (equivalent velocity), displacements and rocking rotations are estimated, discussed and, whenever appropriate, compared with those of Italian seismic codes. Finally, different parameters related to the ground motion records destructiveness are calculated and compared with those obtained for other Italian earthquakes, highlighting how severe the 2016–2017 seismic sequence was. [ABSTRACT FROM AUTHOR]

Larissa, the capital of Thessaly, is located in the eastern part of Central Greece, at the southern border of a Late Quarternary graben, the Tyrnavos Basin. Palaeoseismological, morphotectonic, and geophysical investigations as well as historical and instrumental records show evidences for seismic activity in this area. Previous investigations documented the occurrence of several moderate to strong earthquakes during Holocene time on active faults with recurrence intervals of a few thousand years. The historical and instrumental records suggest a period of seismic quiescence during the last 400-500 years. The present archaeoseismological research, based on a multidisciplinary approach is devoted to improve the knowledge on past earthquakes, which occurred in the area. This study focuses on damages observed on the walls of the scene building of the Great Theatre of Larissa. The Theatre was built at the beginning of the third century BC and consists of a semicircular auditorium, an almost circular arena and a main scene building. Archaeological and historical investigations document a partial destruction of the theatre during the second to first century BC. Recent excavations show that the building complex after it was repaired suffered additional structural damages, probably from seismic loading. The damages investigated in detail are displacements, rotations and ruptures of numerous blocks at the walls of the scene building. In order to test the earthquake hypothesis as cause of the damages a simplified seismotectonic model of the Tyrnavos Basin and its surroundings was used with a composite earthquake source model to calculate synthetic seismograms at the Larissa site for various earthquake scenarios. Horizontal to vertical seismic ratio (HVSR) measurements in the theatre and its vicinity were used to estimate local site effects. The synthetic seismograms are then used as input accelerations for a finite element model of the walls, which simulates seismically induced in-plane sliding within the walls. Results show that some of the surrounding faults have the potential to produce seismic ground motion that can induce in-plane sliding of blocks. Model calculations were used to constrain the characteristics of the ground acceleration and infer the causative fault and earthquake by comparing the calculated and observed distribution of the displacements of the blocks. Ground motions with a PGA at the site of 0.62-0.82 g, which could be induced by an M 5.8-6.0 earthquake on the nearby Larissa Fault, would be sufficient to explain the damage. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]