Negli ultimi anni sono state sviluppate diverse procedure per la modellazione e l’analisi di edifici in muratura. E stata riconosciuta, peraltro, la notevole efficacia dei metodi statici non lineari per la valutazione delle prestazioni... more
Negli ultimi anni sono state sviluppate diverse procedure per la modellazione e l’analisi di edifici in muratura. E stata riconosciuta, peraltro, la notevole efficacia dei metodi statici non lineari per la valutazione delle prestazioni sismiche in termini di resistenza e di spostamento. La consapevolezza dello stretto legame che intercorre tra le distorsioni impresse dal terremoto e il danneggiamento strutturale, nonche la necessita di condurre analisi in controllo di spostamenti per predire la risposta sismica in condizioni di avanzato degrado di resistenza, hanno portato gli autori della presente memoria a formulare una nuova strategia di modellazione e di analisi non lineare degli edifici in muratura. Nel presente articolo vengono trattati gli aspetti salienti connessi a tale metodologia di analisi attraverso una modellazione delle pareti ai macro-elementi, con particolare riferimento ad un nuovo programma di calcolo, il “Codice RAN”, concepito specificamente per la progettazione...
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Historical centers are places where local identity principles and contemporary dynamics of urbanization coexist. They conserve cultural heritage, hence the presence of many historical assets makes these places highly vulnerable and exposed.
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Recent numerical analyses on some types of planar Masonry Combined Systems (MCSs) showed a great variability of the lateral stiffness along the height, following to the mutual interaction between different parallel structural elements.... more
Recent numerical analyses on some types of planar Masonry Combined Systems (MCSs) showed a great variability of the lateral stiffness along the height, following to the mutual interaction between different parallel structural elements. This may induce significant eccentricities between centre of mass and centre of rigidity, in addition to the ones potentially due to U-shaped walls placed at the perimeter of the building or to irregular in-plan frame-wall dual systems. The mixed structure of the building becomes dramatically prone to damage due to twist-induced displacements, so a 3D seismic analysis is required to account for its torsional response. In this paper a matrix algorithm for seismic analysis of structural systems formed by masonry or Reinforced Concrete (RC) shear walls (with or without openings), frames and structural cores, is proposed. Such lateral load-resisting elements are considered to be arbitrarily arranged in plan and subjected to a generic pattern of horizontal...
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In the last decade, probabilistic approaches for flood risk assessment have emerged, often as an extension of more consolidated methods used in probabilistic seismic risk assessment. Nonetheless, only a few studies deal with best-practice... more
In the last decade, probabilistic approaches for flood risk assessment have emerged, often as an extension of more consolidated methods used in probabilistic seismic risk assessment. Nonetheless, only a few studies deal with best-practice methodologies for flood vulnerability assessment and existing approaches lack of an appropriate guidance for their selection. These concerns underline the need for a rational, integrated and complete compendium of all the existing flood-related vulnerability and fragility relationships to be used in a comprehensive probabilistic flood risk assessment framework. Following the same approach used in the guidelines recently developed by the Global Earthquake Model (GEM) Project, this paper presents a preliminary review of the state-of-art regarding existing empirical vulnerability and fragility curves in the context of flood risk. In particular, a worldwide overview is intended in terms of data sources, assets features and also statistical techniques e...
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Soil-Foundation-Structure Interaction (SFSI) has been widely analysed in recent years from theoretical, numerical and experimental viewpoints. Its effects may be largely significant in combined structural systems including masonry or... more
Soil-Foundation-Structure Interaction (SFSI) has been widely analysed in recent years from theoretical, numerical and experimental viewpoints. Its effects may be largely significant in combined structural systems including masonry or Reinforced Concrete (RC) shear walls. Therefore, such models should be analysed taking into account also the foundation and the soil. In this paper a matrix algorithm for the seismic analysis of Masonry Combined Systems (MCSs) including Soil-Foundation-Wall Interaction (SFWI) is proposed. The theoretical study is divided into the following stages: (1) modelling of the soil-foundation interaction; (2) analysis of a flexibly-supported solid shear wall under lateral forces. Finally, the results of some parametric analyses on multi-storey Masonry-RC Combined Systems (MRCSs) are discussed showing that SFWI cannot be neglected, since it affects the distribution of lateral forces between different parallel structural elements.
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Failure of a pipeline carrying gaseous hydrogen can have several effects, some of which can pose a significant threat of harm to people and damage to buildings in its immediate proximity. This paper presents a probabilistic risk... more
Failure of a pipeline carrying gaseous hydrogen can have several effects, some of which can pose a significant threat of harm to people and damage to buildings in its immediate proximity. This paper presents a probabilistic risk assessment procedure for the estimation of damage to people and buildings endangered by high-pressure hydrogen pipeline explosions. Such a procedure provides an evaluation of annual probability of damage to people and buildings under an extreme event using a combination of the conditional probability of damage triggered by an explosion and the probability that the explosion occurs as a consequence of the pipeline failure. The release of hydrogen is simulated using the LimitState:SLAB model and the size of the hydrogen-air cloud in the flammability range is evaluated, then overpressure and impulse generated by the blast are evaluated through the Netherland Organization for Applied Scientific Research (TNO) model, while explosion effects on people and building...
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2. Damage to masonry buildings 6 2.1. Modern residential buildings 6 2.2. Historic building aggregates 7 2.3. Churches 9
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Unreinforced masonry (URM) has been used to build up a large number of structures and infrastructures since ancient times, and is still employed in modern construction. In recent earthquakes, URM buildings have sustained a high degree of... more
Unreinforced masonry (URM) has been used to build up a large number of structures and infrastructures since ancient times, and is still employed in modern construction. In recent earthquakes, URM buildings have sustained a high degree of damage due to in-plane loading, demonstrating a pressing need for retrofitting. In the last years, externally bonded fibre-reinforced polymers (FRPs) and fabric-reinforced cementitious matrices (FRCMs) have been proposed as effective solutions for seismic retrofit of URM walls and their use is rapidly increasing worldwide. In this paper, the in-plane lateral strength of tuff stone masonry walls in both as-built and strengthened conditions is investigated. Diagonal FRP strips and FRCM composite, applied on both sides of walls and through single plies, are considered as strengthening systems. Based on capacity models as well as statistics and probability distributions for material properties, geometry and models, a probabilistic analysis was carried o...
Historical urban centers are often characterized by cavity systems beneath the foundations or underground stories of masonry buildings. This may have an impact on the expected damage induced by earthquake excitations. This paper presents... more
Historical urban centers are often characterized by cavity systems beneath the foundations or underground stories of masonry buildings. This may have an impact on the expected damage induced by earthquake excitations. This paper presents the nonlinear dynamic analysis of a historical multistory building made of stonemasonry loadbearing walls and horizontal diaphragms, taking into account the complex interaction between the foundation system and soil. The aim of this research is to evaluate whether and how the presence of an underground floor and cavity influences the Soil-Foundation-Structure (SFS) interaction. Dynamic analyses of 2D SFS models were performed with the finite difference method (FDM), by varying geotechnical and structural properties such as the soil stratigraphy, the basement depth and the number of building stories. The main results of 234 dynamic linear elastic analyses are presented in a dimensionless format. A new equivalent wave parameter was properly defined to...
Shear behaviour of unit-mortar interfaces is typically characterized through the MohrCoulomb failure model and shear stress versus shear strain diagrams. In porous stone masonry types such as tuff masonry, dilatancy plays also a key role... more
Shear behaviour of unit-mortar interfaces is typically characterized through the MohrCoulomb failure model and shear stress versus shear strain diagrams. In porous stone masonry types such as tuff masonry, dilatancy plays also a key role and shear strength of unit-mortar interfaces at zero confining normal stress is non-zero due to the slip surface’s roughness. To characterize nonlinear shear behaviour for tuff masonry assemblages, direct shear tests were carried out under different pre-compression levels. This paper summarises the experimental program discussing the main results. Empirical formulas are presented to define shear failure at both peak and residual stress levels. Shear deformation capacity, strength degradation, mode II fracture energy, and dilatancy coefficient were computed. Multiple regression analysis was applied to derive a shear response surface including both stress-strain diagrams and the frictional strength model. Constraints on the continuity of both the shea...
The paper deals with the results of a multidisciplinary study aimed at assessing the seismic vulnerability of two historical buildings in a picturesque medieval village in Southern Italy, taking into account the interaction among... more
The paper deals with the results of a multidisciplinary study aimed at assessing the seismic vulnerability of two historical buildings in a picturesque medieval village in Southern Italy, taking into account the interaction among structure, soil and underground cavities. The subsoil model accounted for nonlinear visco-elastic hysteretic behavior, as calibrated on the basis of past and recent geotechnical and geophysical investigations. A strainsoftening constitutive model was adopted to simulate the nonlinear behavior of masonry, according to a macromechanical approach. Some of mechanical parameters were calibrated against experimental data resulting from uniaxial compression tests performed on single-leaf masonry prisms. 2D nonlinear dynamic analyses were performed with the FLAC code on soil-cavity-structure models by applying a reference input motion compatible with the design acceleration spectrum specified by the Italian code of practice. The building performance and its ability...
Seismic events represent nowadays a major challenge for the worldwide scientific community. Besides, novel methodologies for a prompt and efficient response are needed to ensure adequate levels of resilience to global communities,... more
Seismic events represent nowadays a major challenge for the worldwide scientific community. Besides, novel methodologies for a prompt and efficient response are needed to ensure adequate levels of resilience to global communities, allowing they to be capable of recovering from a disaster to a target performance level which is at least equivalent to the pre-event condition. Resilience can also be evaluated as a proxy of the recovered urban damage. Despite the traditional approach to the singlestructure damage assessment, the overall urban environment and mutual connectivity among its components may be considered. As a point in matter, the human part of a city is the most important one, as citizens rule urban dynamics being the principal end-users of local services. Hence, when studying urban environments, a multi-faceted and human-centric approach is required to account for both physical and human components. This means that infrastructure damage can be assessed through a systemic me...
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Abstract Natural and man-made disasters often produce the collapse of multiple structural members at the ground floor of buildings, which may trigger a progressive collapse of the structure. Nonetheless, only a few experimental tests and... more
Abstract Natural and man-made disasters often produce the collapse of multiple structural members at the ground floor of buildings, which may trigger a progressive collapse of the structure. Nonetheless, only a few experimental tests and numerical studies have been carried out to assess the effects of multiple column loss. In this paper, the progressive collapse capacity of gravity-load designed, reinforced concrete (RC) buildings complying with Eurocode 2 is numerically investigated, considering both simultaneous and sequential removal of ground-floor columns. The study focuses on a benchmark RC frame used in previous investigations on single-column loss scenarios, using nonlinear fibre-based capacity modelling and incremental dynamic analysis. Progressive collapse capacity was evaluated at multiple structural scales, in terms of axial strains, beam drifts and gravity load resisted by the structure after column loss. Analysis results allowed the quantification of both load and drift capacities under varying relative location and deactivation times of removed columns, as well as the control point. A comparison with numerical/experimental data highlighted that the sudden loss of two consecutive columns can drastically reduce the load capacity, resulting in a progressive collapse of the RC framed structure. A sequential loss of columns induced either positive or negative variations in load capacity, depending on the ratio between removal times, whereas drift capacity significantly reduced in almost all cases.
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In the last decade, displacement-based seismic design procedures have been recognised to be effective alternatives to force-based design (FBD) methods. Indeed, displacement based design (DBD) may allow the structural engineer to get more... more
In the last decade, displacement-based seismic design procedures have been recognised to be effective alternatives to force-based design (FBD) methods. Indeed, displacement based design (DBD) may allow the structural engineer to get more realistic predictions of local and global deformations of the structure, and hence damage, under design earthquakes. This facilitates the achievement of performance objectives and loss mitigation in the lifetime of the structure. Nonetheless, DBD needs further investigation for some structural types such as masonry buildings. In this paper, a direct displacement based design (DDBD) procedure for unreinforced masonry (URM) buildings is presented and critically compared to FBD. The procedure is proposed for box-type URM buildings with reinforced concrete slabs, bond beams and lintels above openings, which have shown acceptable seismic performance in severe earthquakes preventing out-of-plane failure modes. Seismic design of a three storey brick masonr...
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Displacement-based seismic design has been proved to be a rational procedure allowing the control of the inelastic response for both framed and wall structures under earthquake loading. Nevertheless, the application of this design... more
Displacement-based seismic design has been proved to be a rational procedure allowing the control of the inelastic response for both framed and wall structures under earthquake loading. Nevertheless, the application of this design methodology to masonry buildings still needs to be investigated. In this paper, a direct displacement-based design (DDBD) procedure for unreinforced masonry (URM) buildings is presented and critically compared to force-based design (FBD). DDBD was applied to a three-storey brick masonry building, which was assumed to be located in a high-seismicity site in Italy. Analysis results show that: (1) both the combination of horizontal seismic actions and non-zero accidental eccentricities may induce a significant increase and scattering in strength demands on URM shear walls, especially in near-field earthquake conditions; (2) after design optimisation, construction costs resulting from the proposed DDBD procedure may be about 30% lower than those provided by cu...
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All around the world, non-engineered masonry constructions (NECs) typically have high vulnerability to seismic ground motion, resulting in heavy damage and severe casualties after earthquakes. Even though a number of computational... more
All around the world, non-engineered masonry constructions (NECs) typically have high vulnerability to seismic ground motion, resulting in heavy damage and severe casualties after earthquakes. Even though a number of computational strategies have been developed for seismic analysis of unreinforced masonry structures, a few studies have focussed on NECs located in developing countries. In this paper, different modelling options for finite element analysis of non-engineered masonry buildings are investigated. The goal of the study was to identify the modelling option with the best trade-off between computational burden and accuracy of results, in view of seismic risk assessment of NECs at regional scale. Based on the experimental behaviour of a single-storey structure representative of Indian non-engineered masonry buildings, the output of seismic response analysis of refined 3D models in ANSYS was compared to that of a simplified model based on 2D, nonlinear, layered shell elements i...
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Despite significant research advances on the seismic response analysis, there is still an urgent need for validation of numerical simulation methods for prediction of earthquake response and damage. In this respect, seismic monitoring... more
Despite significant research advances on the seismic response analysis, there is still an urgent need for validation of numerical simulation methods for prediction of earthquake response and damage. In this respect, seismic monitoring networks and proper modelling can further support validation studies, allowing more realistic simulations of what earthquakes can produce. This paper discusses the seismic response of the “Pietro Capuzi” school in Visso, a village located in the Marche region (Italy) that was severely damaged by the 2016–2017 Central Italy earthquake sequence. The school was a two-story masonry structure founded on simple enlargements of its load-bearing walls, partially embedded in the alluvial loose soils of the Nera river. The structure was monitored as a strategic building by the Italian Seismic Observatory of Structures (OSS), which provided acceleration records under both ambient noise and the three mainshocks of the seismic sequence. The evolution of the damage ...
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Robustness of reinforced concrete (RC) structures is an ongoing challenging research topic in the engineering community. During an extreme event, the loss of vertical load-bearing elements can activate large-deformation resisting... more
Robustness of reinforced concrete (RC) structures is an ongoing challenging research topic in the engineering community. During an extreme event, the loss of vertical load-bearing elements can activate large-deformation resisting mechanisms such as membrane and catenary actions in beams and floor slabs of cast-in-situ RC buildings to resist gravity loads. However, few studies have been conducted for precast concrete (PC) buildings, especially focused on the capacity of such structures to withstand column loss scenarios, which mainly relies on connection strength. Additional resistance resource and alternate load paths could be reached via tying systems. In this paper, the progressive collapse resistance of a PC frame building is analyzed by means of nonlinear dynamic finite element analyses focusing on the fundamental roles played by beam-to-column connection strength and tying reinforcement. A simplified modelling approach is illustrated in order to investigate the response of such...
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Precast concrete (PC) plays an important role in the industrialization processes of buildings, so it is critical to study the seismic performance of such structures. Several experimental and numerical studies have been conducted to... more
Precast concrete (PC) plays an important role in the industrialization processes of buildings, so it is critical to study the seismic performance of such structures. Several experimental and numerical studies have been conducted to investigate the behavior of PC beam-to-column connections. However, most of the previous studies neglect the contribution of slabs. In light of this, this paper presents a numerical simulation method for dry connected beam-slab assemblies based on the layered shell element available in OpenSees. The beams were modeled with fiber elements, while the slabs were modeled with layered shell elements. The developed model was validated by simulating a typical beam-slab assembly test, with the characteristics of hysteretic performance found to be well reflected by the model. Moreover, a parametric study was performed to quantify the influence of slab parameters. The results showed that the thickness of the slab had a significant effect on the hysteretic performan...