Figure - uploaded by Giulio Zuccaro
Content may be subject to copyright.
Source publication
In the framework of risk assessment at national and regional scale, the analysis of collapse mechanisms induced by seismic accelerations constitutes a useful tool to understand the behaviour of masonry structures and to plane mitigation strategies and rehabilitation interventions. In this perspective, the objective of the present study is the ident...
Similar publications
The low masonry structure is the most commonly applied building type in rural China. It is possible to install small-diameter, low cost, and easily constructed laminated rubber bearing (LRB) components. Isolation technology has broad application prospects in rural buildings. We developed a small-diameter LRB in this study wherein the isolation laye...
Masonry aggregates have developed throughout city centres of Europe due to a centuries-long densification process that generally lacked consistent planning or engineering. Adjacent units are connected either through interlocking stones or a layer of mortar. Without interlocking stones, the connection between the units is weak, and an out of-phase r...
The paper presents a detailed report on a large sample of masonry churches damaged by the 2016–2017 Central Italy seismic sequence. The first part of the work analyses the seismic sequence to give an overview of the occurred events in terms of both ground motion parameters and macro-seismic intensities. The surveyed data are organized into a databa...
Citations
... Various methodologies have been proposed to determine collapse multipliers for both in-plane and out-of-plane failure modes in typical masonry structures. These include approaches that consider different failure mechanisms and employ advanced analytical techniques [38][39][40] or numerical techniques [41]. Additionally, sophisticated limit analysis techniques have been developed to identify the most likely failure mechanisms in three-dimensional masonry towers, considering predetermined failure modes such as rocking, Heyman's diagonal cracking [42], and base shear sliding. ...
Many Italian historic buildings are located in earthquake-prone areas and, therefore, need effective seismic evaluations. Most widespread commercial codes are based on the Equivalent Frame Model (EFM). To investigate their reliability, particularly to assess the effect of tie-rod retrofitting interventions, the present research applies an EFM approach via 3Muri software to a detailed 3D digital model of Villa Vannucchi, a heritage building in southern Italy. The combined use of 3Muri for the 3D global behaviour and linear kinematic approaches for the 2D out-of-plane response shows the need for the installation of tie-rods. Looking at the 2D main facade, the effectiveness of 3Muri in capturing the beneficial effect of tie-rods is investigated against parametric analyses carried out with a standard limit analysis block-based method (BBM). Specifically, using the exact EFM's discretization and boundary conditions, the 3Muri results are benchmarked against the BBM adopting two modelling strategies: BBM pushover analysis with the same modelling strategy and loading conditions used by 3Muri, and BBM tilting tests. With the first strategy, it is shown that BBM provides results in good agreement with 3Muri; however, these results are independent of the tie-rod tension and presence because of inappropriate modelling of loading conditions. Conversely, the second strategy overcomes this drawback by better capturing the positive influence of the tie-rods both in terms of collapse mechanisms and an improved base shear capacity. The results of this research suggest that limit analysis represents a key, useful, and viable tool that needs to be integrated with EFM results in order to better capture the real effectiveness of tie-rod strengthening interventions, allowing for more sustainable consolidation strategies.
... This can be achieved by employing structural models and analyses that balance the accuracy and the efficiency. Masonry structures, for instance, can be modelled by using simplified analytical solutions (Zuccaro et al. 2017) or more advanced models that make use of the Finite Element Method (FEM). In this last case, great accuracy is achieved by micro-models which describe the single component of the walls (brick, mortar and their interface) and take into account the distribution of the mortar joints (Lourenco and Rots 1997;Formica et al. 2002). ...
... Recently, an approach based on the vulnerability index and static nonlinear analyses and an equivalent frame of the masonry structure has been proposed (Nikolic et al. 2021). Fragility functions which consider the out-ofplane behaviour of masonry structures using a failure mechanism approach are presented by D'Ayala (2005); Zuccaro et al. (2017). The automated mechanical vulnerability analysis of masonry aggregates has been recently proposed by Leggieri et al. (2021). ...
... In particular, simple rocking and vertical flexure are considered in the present work. The analysis, whose details can be found elsewhere (Newsoft 2021; Zuccaro et al. 2017), provides for each structure and for each direction of the seismic load, the value of a g that causes the activation of the first mechanism, that is defined as a l g . When mechanical-based methods are used, a numerical interpretation of EMS-98 damage grades is required. ...
The paper presents a mechanical-based framework for the evaluation of local-scale
seismic fragility curves. The approach is oriented to a seismic vulnerability assessment of unreinforced masonry buildings and makes use of basic exposure data easily obtained from survey or available in existing database. An efficient finite element model and static nonlinear analyses are employed to assess the structural behaviour. The mechanical-based fragility curves are evaluated using Monte Carlo simulations that allow to account for the uncertainties propagation. The proposed approach is tested on a case-study regarding the city centre of Cosenza, in southern Italy, using exposure information available from CARTIS database.
... Consequently, global assessment is not usually sufficient and additional verifications must be conducted to ensure safety against local collapse. The local assessment is highly dependent on the choice of a deformation mechanism whose boundary conditions are usually unknown [57]. The choice of failure mechanism is mostly based on the analytical modal response and is dependent on the tensile stress distribution within localized vulnerable areas. ...
The seismic performance assessment of heritage architecture presents many challenges due to the restrictions set forth by the conservation principles to protect the associated social and cultural values. These buildings are typically characterized by unreinforced masonry walls connected by tie-rods, vaults, and wooden floors. The era of construction dates to the time when seismic design regulations were largely unknown, making heritage structures potentially vulnerable to earthquake damage. This study presents the seismic performance assessment of the Jesuit College located in the southern part of the Old City of Dubrovnik. A series of field surveys were conducted to qualitatively examine the material composition and obtain geometrical details in part of the Croatian Science Foundation research project IP-2020-02-3531 entitled “Seismic Risk Assessment of Cultural Heritage in Croatia—SeisRICHerCRO”. The structural response is thoroughly investigated by means of a complex finite element model calibrated using the frequencies determined from ambient vibration measurements and material characteristics obtained from the literature review of representative cultural heritage buildings. The seismic performance is evaluated using linear static and response spectrum analysis in accordance with Eurocode 8 guidelines for the demand seismic action level. The numerical analysis indicates several structural components in the building exhibiting high shear stress concentration and exceeding the elastic tensile limit under the demand ground acceleration level. The assessment further reveals substantial out-of-plane bending of vulnerable wall components (identified by local mode shapes) at low peak ground acceleration levels. The stress concentration in numerous structural components leads to the identification of vulnerable zones where retrofitting measures are essentially required.
... In the existing literature, few contributions have taken the influence of uncertainties on the seismic response of masonry walls into due account. In these contributions, uncertainties were usually modeled by means of linear and nonlinear static approaches for instance through Monte Carlo Simulations (MCS) [33,34], as well as by means of logic trees [35,36]. ...
... The fragility curves including uncertainties have been validated through a Monte Carlo Simulation (MCS) and compared with curves available in the scientific literature [33]. ...
... The fuzzy-like fragility curves are delimited by curves with μ = 0 which represents the least plausible values and a curve with μ = 1 which represents the most plausible value. We compare them with the fragility curves present in the technical literature [33] to validate them and evaluate the sensitivity to the uncertainties. The curves used for the comparison are based on a study on a regional scale of the local collapse mechanisms of 250.000 buildings present on the national territory. ...
... (i) collapse mechanism-based methods, in which kinematic chains are used to define and evaluate the collapse multipliers corresponding to possible failure mechanisms. Non-linear static or pushover analyses are then adopted to define capacity curves (Bernardini et al., 1990;Lagomarsino and Podesta, 2004;Zuccaro et al., 2017); (ii) capacity spectrum-based methods whose use allows to compute predetermined capacity curves for each building typology. The capacity curve is then intersected with the seismic demand to derive the performance points for different damage thresholds (D'Ayala et al., 2013;Ansal, 2012;Fajifar, 2000); (iii) fully displacement-based methods, where buildings are modelled through an equivalent single-degree-of-freedom system. ...
... Several methods have been proposed to provide collapse multipliers for in-and out-of-plane collapse mechanisms of ordinary masonry building stocks (Bernardini et al., 1990;Bernardini et al., 2008a;Bernardini et al., 2008b;Zuccaro et al., 2017;Donà et al., 2020), churches (Lagomarsino and Podesta, 2004;DPCM, 2011) and towers (Torelli et al., 2019) at the building scale. Sophisticated limit analysis-based methods have also been developed to define the most probable failure mechanism of 3D masonry towers at the building scale (Milani, 2019) considering predefined mechanisms such as rocking, Heyman's diagonal cracking, and base shear sliding; an optimisation algorithm finds the most probable mechanism by minimising the corresponding failure multipliers. ...
... Comparison between PRD-based fragility curves (dashed lines) and the ones (solid line) related to the first damage mechanism proposed in (Zuccaro et al., 2017). ...
The high seismic hazard of the Italian territory and the vulnerability of its historic masonry heritage require the development of fragility curves that must be increasingly reliable and robustly correlated to exposure. To date, national-scale seismic risk analyses mainly use empirical curves derived from the statistical analysis of damage induced by past events. These curves have shown good reliability, but they correlate only with a few typological-structural characteristics of the building, such as the number of floors, the vertical structure typology or the construction period. The present research paper aims to overcome this limitation with a hybrid approach that provides a better exposure characterisation. Specifically, the proposed strategy integrates the SAVE and Piecewise Rigid Displacement (PRD) methods. SAVE is an empirical approach based on the damage assessment due to past seismic events used to identify a seismic behaviour of a structure, while the PRD method is a numerical approach that solves the boundary value problem for normal, rigid, no-tension material. It can model different structural typologies, and as a result, it also provides the value of the horizontal static multiplier that drives the masonry construction to collapse. An extended numerical campaign is carried out considering a sample of 750 masonry buildings distributed throughout the Italian territory and extracted from the PLINIVS typological database. Looking at each construction, first, a PRD analysis is conducted to define its seismic capacity, paying special attention to modelling construction details. After that, the SAVE method is used to classify the construction in a specific seismic vulnerability class, i.e., from A to C, with decreasing vulnerability. All the buildings belonging to the same class are then collected, and three fragility curves representative of the collapse state (one for each vulnerability class) are derived and validated against empirical and analytical ones commonly adopted in the Literature. The integrated methodology shows a good agreement between simulations and observations, confirming the viability of the proposed hybrid methodology for the large-scale assessment of masonry buildings, providing an effective strategy to plan mitigation and rehabilitation interventions.
... This can be achieved by employing structural models and analyses that balance the accuracy and the efficiency. Masonry structures, for instance, can be modelled by using simplified analytical solutions (Zuccaro et al. 2017) or more advanced models that make use of the Finite Element Method (FEM). In this last case, great accuracy is achieved by micro-models which describe the single component of the walls (brick, mortar and their interface) and take into account the distribution of the mortar joints (Lourenco and Rots 1997;Formica et al. 2002). ...
... Recently, an approach based on the vulnerability index and static nonlinear analyses and an equivalent frame of the masonry structure has been proposed (Nikolic et al. 2021). Fragility functions which consider the out-ofplane behaviour of masonry structures using a failure mechanism approach are presented by D'Ayala (2005); Zuccaro et al. (2017). The automated mechanical vulnerability analysis of masonry aggregates has been recently proposed by Leggieri et al. (2021). ...
... In particular, simple rocking and vertical flexure are considered in the present work. The analysis, whose details can be found elsewhere (Newsoft 2021; Zuccaro et al. 2017), provides for each structure and for each direction of the seismic load, the value of a g that causes the activation of the first mechanism, that is defined as a l g . When mechanical-based methods are used, a numerical interpretation of EMS-98 damage grades is required. ...
... Moreover, hysteretic models can be used in order to reproduce the behavior of more complex systems for which nonlinear analysis represents the sole reliable strategy to estimate structural responses (Lima et al. 2018;De Angelo et al. 2019;di Cosmo et al. 2018;Andreaus et al. 2018;Castellano et al. 2019) and their collapse mechanisms (Zuccaro et al. 2017). ...
... To accurately evaluate the nonlinear response of such systems, appropriate time integration methods, having specific stability, accuracy, and computational efficiency properties, need to be employed to numerically solve the nonlinear equilibrium equations characterizing the discrete structural model of such systems (Wilson 2002). ...
... In this section, we present Newmark's family of methods since it represents one of the widely used families of conventional time integration methods available in the literature (Nagarajaiah et al. 1991;Wilson 2002;Greco et al. 2018). ...
The chapter presents a generalized formulation of time integration methods that allow for the numerical solution of the nonlinear equilibrium equations characterizing mechanical systems having hysteretic behavior. Two families of time integration methods are derived from such a generalized formulation: the celebrated Newmark’s family of methods and Chang’s family of explicit methods. The former is presented since it represents one of the most employed families of conventional time integration methods available in the literature. On the contrary, the latter is illustrated since it is one of the most efficient families of recently developed structure-dependent time integration methods. For each family, the formulation, the expression for the evaluation of the unknown generalized displacement, velocity, and acceleration vectors, as well as the main numerical properties are first presented. Then, some instances as well as the implementation scheme of each family are illustrated. Finally, nonlinear time history analyses are performed on a rate-independent hysteretic mechanical system, characterized by a stiffening behavior and subjected to an external generalized random force, to illustrate the numerical performance, in terms of accuracy and computational efficiency, of some methods selected within the above-described families.
... In fact, some provisions were developed in order to facilitate handmade-oriented computations in which the human designer is weak in performing large amounts of calculations, while it is highly skilled in making qualitative and theoretical considerations (Zuccaro et al. 2017). On the contrary, in computer-aided design, structural software easily handles great computational efforts, while it is barely reliable in making even simple qualitative choices. ...
Response spectrum analysis represents the preferential strategy to analyze and design civil engineering structures subjected to seismic actions. Nevertheless, most structural codes were developed by following hand computation-oriented philosophies so that their prescriptions can be hard to be implemented in finite element frameworks and often prevent the use of innovative strategies. This contribution presents a review of innovative tools focused on reinforced concrete framed structures aiming to establish a possible organic workflow for design procedures. Some pivotal issues typical of such a structural typology are hereby addressed, and particularly, global torsion and capacity checks in the presence of axial force–biaxial bending responses. This has been done by correlating innovative solutions such as torsional spectra, seismic envelopes, and limit analysis and by presenting a numerical procedure capable of performing capacity checks of reinforced concrete cross sections. The presented strategy aims to be a computationally efficient and exhaustive procedure to be used within the framework of finite element analysis.
... In the literature, there are many works related to risk analysis, either in a broad sense or to some specific factor. Some specific studies on the vulnerability can be found in [1][2][3][4][5][6][7][8][9][10] and on the exposure in [11,12] Regarding the costs analyses, some works are reported in [13,14] and on the multi-criteria, there are [15][16][17][18][19]. ...
Italy is a country with high seismic hazard, however since the delay in the seismic classification of the national territory, most of the existing building heritage does not comply with the current technical standards for buildings. The seismic events that have hit different Italian regions in recent years have highlighted the complexity of the challenge for the public bodies both in the emergency management and post-event reconstruction and in the planning of effective risk prevention and mitigation measures to be implemented in ‘peacetime’. These difficulties concern, in particular, the capacity to properly manage the financial and technical resources available and to identify the intervention priorities throughout the entire emergency cycle. For correct management, the priority is to quantify and localize, through simulations, the quantification of probable damages and to evaluate in terms of cost-benefits the possible alternative strategies for mitigation, also taking into account the potential, in terms of cost-effectiveness, of integrated measures for seismic and energy retrofitting. In this framework, the project CAESAR II (Complementary Analyses for Emergency planning based on Seismic Risks impact evaluations) has been developed as a Decision Support System for Public Authorities in charge of developing Disaster Risk Reduction plans, with the possibility of programming mid to long-term investments for public and private properties, as well as defining custom financial support mechanisms and tax incentives.
... In-plane behaviour activates the walls parallel to the direction of the horizontal loads, while out-of-plane behaviour involves walls subjected to horizontal actions orthogonal to their plane. Recent seismic events outlined great vulnerability of masonry structures to the out-of-plane loading that cause wall's partial or total collapse (Zuccaro, Dato, Cacace, de Gregorio, & Sessa, 2017). The main failure mode occurs due to overturning of the wall and is governed by lack of the connections between the walls. ...
The damage caused by earthquakes in historical masonry constructions is generally determined by the collapse of single portions which detach form the structure and fail by overturning. These mechanisms are mainly governed by the discrete nature and geometry of block units. Analyses based on explicit micro-modelling where each block is considered separately are therefore of increasing importance. The main goal of this thesis is to offer a robust tool for seismic assessment of masonry structures under either quasi-static or dynamic loading. The effective discrete nature and geometry of masonry is taken into account through the Distinct Element Method (DEM).
Numerical procedures that automatically detect the collapse mode and follow the evolution of the analysis up to collapse are proposed. The developed algorithms are aimed at performing time-history, pulse dynamic and pushover analyses.
Potentialities and limits of the implemented approach are shown through comparison with the traditional analysis based on simplified rigid-block kinematics and experimental results.
Finally, DEM-based methodologies for modelling retrofitting solutions to increase the seismic capacity are proposed.
