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The preservation of trees in urban and archeological areas is a theme of particular relevance. Modern systems of monitoring, together with approaches for deriving the main characteristics of trees influencing their response toward extreme events, are nowadays at the basis of a growing number of studies. The aim of the present paper is the dynamic identification of trees carried out by employing an approach which combines a simple data-acquisition system, direct and ambient sources of excitation, and different data-processing methods. In particular, using a single accelerometer placed at different sections of the trunk and considering excitations induced by either pulling tests or ambient vibrations, the derivation of the main frequencies and levels of modal damping characterizing the dynamic response of a sour cherry tree (Prunus cerasus) is carried out. A finite element model of the tree is also carried out to support the validation of the proposed approach and further analyze the derived outcomes. The obtained results underline the feasibility of the proposed approach in deriving information useful for assessing the behavior of trees toward dynamic actions and, consequently, of particular relevance for the identification of possible damages induced by variations in terms of dynamic characteristics (frequencies) and damping.

[EN] This paper contains a numerical study based on tests carried out at the Universitat Politècnica de València (Spain) on a U-shaped unreinforced and TRM-reinforced masonry building structure subjected to horizontal loads. The masonry was composed of clay bricks with 10 mm thick mortar joints arranged in an English bond manner. The prototype was tested by applying pseudo-dynamic displacement-driven cycles and varying cyclic amplitudes and frequencies in two different stages: (i) on the as-built structure and (ii) after the repair and the application of Textile Reinforced Mortar (TRM) material. A series of non-linear numerical simulations were performed adopting the ABAQUS/Explicit FE software. The FE calibration was carried out using the results obtained during ambient vibration tests. Simulations were then used to evaluate the effectiveness of the proposed TRM technique to increasing the strength of low-rise old masonry building structures., The authors would like to express their gratitude to the Spanish Ministry of Economy, Industry and Competitiveness for the funding provided (BIA 2014-59036-R-AR), and also to the Grupo Mapei and Grupo Puma for their invaluable assistance during the experimental tests.

The preliminary results of an ambient-vibration based investigation conducted on a large sample of historic masonry towers in the Marche region (Central Italy) are presented, with a focus on the belfry of Collegiata of Santa Maria in Visso (Italy). The assessment procedure includes full-scale ambient vibration testing, modal identification from ambient vibration responses, finite element modeling and dynamic-based identification of the uncertain structural parameters of the model. As the most doubtful parameters, the modulus of elasticity of the masonry is adjusted to achieve the experimental results with numerical model by simple operations.

Italy is a high seismic risk country since 1900 more than 30 earthquakes with magnitude greater than Mw=5.8 have occurred, and the last one is the Central Italy seismic sequence. The first shock occurred in the 24 August (Mw=6.2) followed by another stronger quake in the 30th October (Mw=6.5). It hit the regions of Marche, Umbria, and Abruzzo heavily causing many deaths, injuries and extensive damages on the cultural heritage. This paper analyses the church of San Francesco in Amadola, located in the Marche region that has been considered condemned for the severe damages reported after these earthquakes. The church is globally analyzed by the application of nonlinear static analysis on a Finite Element Model where the nonlinearity of masonry is taking into account with a proper constitutive law. The study wants to prove how global analysis combined by the local analysis can reproduce the behavior of this structure during a quake, showing that it can repeat the real damages produced by earthquakes.

Climate change and the raising number of extreme events, such as severe floods, has increased the attention on their effects on urban systems. Urban floods generate important hydrodynamic loads on building and this work proposes a first systematic study on the actions generated by floods with different characteristics (depth, velocity and incidence angle) on masonry buildings. The study is carried out with experimental tests reproducing a masonry bay with scale 1:10, while the effect of the flow hitting the building has been obtained by moving the building in the water at rest. The pressure generated by the fluid at the four walls of the building was recorded using pressure transducers. It has been found that the overpressure acting on the building depends on the flow characteristics in different manner for the frontal, lateral and rear walls. Further, the incidence angle plays a major role in the generation of a pressure gradient along the impacted wall, and significantly affects both peak frequency and spectral energy. Use of theoretical models suggests that (i) the drag coefficient of the building decreases with the Froude number, and only slightly depends on the incidence angle, and (ii) the blocking effect largely affects the hydrodynamics around the structure.

International audience; The non-smooth contact dynamics method was selected to investigate the damage occurred to typical masonry churches (namely Apennine churches) belonging to Central Italy areas affected by the seismic activity started in 2016. The investigated buildings show discontin-uous dynamics since the optioned method gave the chance to properly model the temples as multi rigid body systems using the Signorini's impenetrability condition and the dry-friction Coulomb's law, achieving a thoughtful response to ground seismic solicitations. The results provided by the assessment grant an overview of the most common damages and failure mechanisms, giving the guidelines to restoration projects that fully respond to structural needs.

Central Italy Earthquakes occurred in 2016 pointed out once more the vulnerability of Cultural Heritage (CH), especially for what concerns bell-towers since they tend to get dramatically damaged du...

This paper presents a new damage detection index for arched structures, which can easily and quickly provide an estimate of their integrity. The results from eight laboratory tests performed on both reinforced and unreinforced adobe arches are used to define the index. The arches are damaged up to collapse using pseudo-static test cycles carried out by applying progressive controlled displacements at third span. The test records allow to follow the stiffness degradation of each arch by plotting the relative force-displacement curves, as well as to track their frequencies variation during the damage evolution by means of dynamic identification tests performed at the end of each cycle. The new index considers the bending moment as the main cause of damage for the analysed arches; therefore, starting from the bending stiffness, a damage indicator was developed and experimentally validated, as function of the frequency reduction, respect to the undamaged scenario. Finally, the index is also validated for diferente types of arch collapse mechanisms through Finite Element Modeling., (undefined)

This paper presents the experimental results obtained from tests on a 2/3 scale U-shaped masonry building constructed in one of the ICITECH laboratories at the Universitat Politecnica de Valencia (Spain). The prototype measured 3.31 × 4.19 m2 by 2.15 m high and had a wall thickness of 230 mm. The masonry was composed of 230 × 110 × 50 mm3 solid clay bricks with approximately 10 mm-thick mortar joints arranged in English bond. The tests were aimed at evaluating the effectiveness of cement-based reinforcing materials (Textile Reinforced Mortar) applied to weak masonry substrates severely damaged by horizontal loads such as those induced by a seismic event. The tests were carried out in three phases: (i) testing of the as-built structure, (ii) application of one external layer of TRM to restore the masonry’s original load-bearing capacity and then (iii) testing the TRM-strengthened structure. Dynamic behaviour was monitored by both traditional and fibre optic sensors (FO), including 28 Linear Variable Displacement Transducers (LVDTs) and 3 long-gauge optical sensors. Strengthening effectiveness was evaluated by several parameters: hysteretic curves, strength degradation, computed cumulative energy dissipation and cracking mechanisms. TRM reinforcement was shown to significantly extend the load-bearing and displacement capacity of the masonry prototype, reducing seismic-induced damage applied by pseudo-dynamic excitation, although it had a limited effect on cumulative energy dissipation.

The dynamic behaviour and the seismic vulnerability of different masonry “Apennine Churches”, dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini’s law, concerning the impenetrability between the rigid bodies, and by the Coulomb’s law, regarding the dry-friction model. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the churches permitted to validate the used approach. Finally, from the results and conclusions of these cases study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe.

Background:In October 2016, two major earthquakes occurred in Marche region in the Centre of Italy, that resulted in widespread damage. The second one strokes Norcia, Visso, Arquata del Tronto, Accumoli and Amatrice, causing a lot of damages to cultural heritage of the cities of Tolentino, San Severino, Camerino and Ascoli Piceno, where the church ofSanta Maria della Caritàis located.Introduction:The church has high historical, architectural and social value for the city of Ascoli Piceno, because it is the only one that is opened to the devotees all time in the day and night. From the structural point of view, the church has a long and important annex to the north, which was later built with respect to the church, and after the L’Aquila earthquakes (2009) damages, the church was subjected to a retrofit intervention, in order to obtain a better “box-like behavior”.Objective:This paper addresses how the relevant annex influenced the seismic response of this historical complex and how, more generally, this kind of asymmetric mass may affect the behavior of historic churches.Results and Conclusion:The results indicate that the presence of annex plays a significant role in the dynamic response of the church and affects the distribution of damages in the whole building. The results of the seismic simulation agree with the observed damage.

The current work presents the first results on the determination of reliable numerical models of earthen blocks under different loading conditions. Uniaxial compression and 3-points bending tests were performed. Experimental behavior was modelled with a nonlinear model able to describe the cracking behavior. The simplified approach based on macro-modelling shows a satisfactory accuracy and low computational costs. The numerical results are in good agreement with the post-elastic behavior observed in the experimental campaign.

The subject of this work is the Sant'Agostino Sanctuary in Offida (Italy); we investigated both the dynamic behavior and the seismic vulnerability of the complex, used nowadays in its parts as school building, oratory, and church. Offida is in central Italy; the village has been severely damaged by the last seismic events of 2016. The sanctuary was heavily damaged by the earthquake of 24 August 2016. We recurred to finite elements to estimate the vulnerability of the sanctuary and its dynamic response, considering masonry's non-linear behavior by means of proper constitutive assumptions. To estimate how the monastery bears the lateral loads related to the expected demands resulting from seismic actions (N2 method) using non-linear static analysis (Pushover), we recurred to a homogenized material and smeared cracking and crushing constitutive law. As may be remarked by observing buildings that share the same features of the sanctuary and, moreover, by comparing seismic demand vs. capacity, the structure is prone to massive damage leading to collapse. The paper underlines how advanced numerical analysis grants fundamental data on how historical masonry buildings behave under seismic action, providing a method that may easily be implemented at historic monasteries in Europe.

The present research paper properly focuses on the dynamics and failure mechanisms of the masonry “Apennine Church” of Santissimo Crocifisso in Pretare, municipality of Arquata del Tronto in the province of Ascoli Piceno (Marche region, Central Italy). Such a peculiar structural type traditionally characterizes the intense seismic area of Central Italy, unfortunately almost totally damaged by the recent shock sequence of 2016. Advanced numerical modeling through discontinuous and continuous approaches were here utilized to have an insight into the dynamic properties and behavior of the structure under strong nonlinear dynamic excitations. In the discrete element approach, the non-smooth contact dynamics method, implemented in LMGC90©, was applied, adopting a full 3D detailed discretization. The church was schematized as an arrangement of rigid blocks, subjected to sliding by friction and perfect plastic collisions, with a null restitution coefficient. In the finite element approach, the concrete damaged plasticity model available in Midas FEA NX© was involved. This model allows reproducing the tensile cracking, the compressive crushing, and the degradation of the material under cyclic loads. Finally, the numerical analyses provided a valuable picture of the actual behavior of the church, thus giving useful hints for future strengthening interventions.

© 2020 European Association for Structural Dynamics. All rights reserved. In the present paper has been reported the Non-Smooth Contact Dynamics method (NSCD) used for the damage evaluation of the multiple leaf masonry walls of the medieval fortress of Arquata del Tronto, strongly affected by the last Centre Italy earthquakes of August and October 2016. Pursuing this approach, a system of rigid blocks has been used for the assembly of the masonry structure. By means of contacts between blocks, which are governed by the Signorini's impenetrability condition and by dry-friction Coulomb's law, the building exhibits discontinuous dynamics. Finally, the NSCD method has proved to be an effective instrument for investigating the dynamical behaviour of the masonry structures under the ground seismic accelerations. Indeed, several possible failure mechanisms have been confirmed through the numerical results, which have given a deep insight into the seismic vulnerability of this damaged medieval fortress.