Search

This paper presents an experimental program in which 16 full-scale clay brick unreinforced masonry walls were constructed and tested under in-plane cyclic shear loading. These walls have been divided into four sets of nominally identical specimens constructed with the same masonry units from the same mortar composition by the same mason and cured for a consistent period of time. The repeatability of these tests allows for the variability of the peak in-plane shear capacities of these wall configurations to be investigated. Furthermore, these tests were supplemented with material characterization tests, examining the tensile, shear, compressive, and elastic properties of the masonry utilized in this study. In addition, assessments of the accuracy of the current Australian standard for masonry design, as well as that of other expressions found in the literature, have been made. The findings of this analysis indicate that the Australian standard maintains significant limitations in its ability to correctly determine the shear capacity and failure mechanism of masonry shear walls. This error is reduced, but not wholly mitigated through the application of the deterministic equations present in the other design guides. [ABSTRACT FROM AUTHOR]

Unreinforced masonry buildings are highly vulnerable to earthquake damage due to their limited ability to withstand lateral loads, compared to other structures. Therefore, a detailed assessment of the seismic response and resultant damage associated with such buildings becomes necessary. The present study employs machine learning models to effectively predict the seismic response and classify the damage level for a benchmark unreinforced masonry building. In this regard, eight regression-based models, namely, Linear Regression (LR), Stepwise Linear Regression (SLR), Ridge Regression (RR), Support Vector Machine (SVM), Gaussian Process Regression (GPR), Decision Tree (DT), Random Forest (RF), and Neural Networks (NN), were used to predict the building's responses. Additionally, eight classification-based models, namely, Naïve Bayes (NB), Discriminant Analysis (DA), K-Nearest Neighbours (KNN), Adaptive Boosting (AB), DT, RF, SVM, and NN, were explored for the purpose of categorizing the damage states of the building. The material properties of the masonry and the earthquake intensity were considered as the input parameters. The results from the regression models indicate that the GPR model efficiently predicts the seismic response with larger coefficients of determination and smaller root mean square error values than other models. Among the classification-based models, the RF, AB, and NN models effectively classify the damage states with accuracy levels of 92.9%, 91.1%, and 92.6%, respectively. In conclusion, the overall performance of the non-parametric models, such as GPR, NN, and RF, was found to be better than that of the parametric models. [ABSTRACT FROM AUTHOR]

Masonry structures, particularly those used in developing countries and in historic buildings, typically consist of unreinforced masonry (URM) walls connected by timber or reinforced concrete elements. This study proposes enhancements to the existing two-dimensional (2D) deformable frame model (DFM) to enhance its ability in simulating masonry walls with a specific focus on accurately predicting the transient dynamic response of three-dimensional (3D) masonry structures while maintaining a minimal number of degrees of freedom (DOF). For the modeling of URM walls, the DFM framework employs elastic beams and diagonal struts with nonlinear constitutive behavior. Structural elements, such as reinforced concrete or timber reinforcements, are represented using conventional beam finite elements. This paper first reviewed the current DFM configuration, which primarily addresses the in-plane (IP) behavior of URM structures. It then introduced modifications tailored for 3D structural analysis. The reliability of the enhanced model was validated through two approaches. First, a modal analysis compared the results from the updated DFM with those from a reference 3D model based on cubic finite elements. Second, a shaking table experiment conducted on a half-scale masonry house was simulated. The findings demonstrate that, despite its limited number of DOF, the updated DFM effectively captures the main natural vibration modes. Furthermore, it shows the model's ability to predict the nonlinear transient dynamic response of 3D masonry structures with accuracy and limited computational time. [ABSTRACT FROM AUTHOR]

Many historical buildings employ masonry cross-vaults as flooring systems. The structural response of such cross-vaults to seismic excitation still needs to be fully understood and requires investigation through experimental studies or accurate numerical simulations. This article presents a finite element discontinuum micromodelling technique to simulate a full-scale mortared masonry cross-vault (unstrengthened and subsequently strengthened with textile-reinforced mortar) recently tested on a shake table as part of a blind prediction competition. The numerical technique uses shell elements to model the brick and mortar geometry explicitly within the STKO+OpenSees finite element framework. Both brick and mortar materials are modeled using an advanced damage-plasticity constitutive model, addressing potential convergence issues associated with strain-softening materials through a novel implicit-explicit integration algorithm. The numerical models predicted the failure mechanisms and crack patterns in close agreement with the experimental results. The strengthened model displayed severe cracks spreading across a larger part of the cross-vault, whereas the unstrengthened model exhibited in-plane shear failure along the groin lines. The strengthened vault showed an almost twofold increase in peak ground acceleration capacity, demonstrating the effectiveness of textile-reinforced mortar. The proposed numerical technique will be helpful in the design of effective retrofit measures for heritage structures. [ABSTRACT FROM AUTHOR]

This work presents the numerical simulations of shaking table tests of a full-scale masonry cross vault. The boundary conditions simulate the presence of a continuous lateral wall and of a colonnade-between-naves condition. The seismic action is applied along the longitudinal direction of the specimen, with increasing amplitude. The model used for the simulations allows for the elastic finite element modelling of masonry units and the discrete element modelling of the interfaces between them. A tension cut-off governs the interface: no tensile stress can be transmitted once this strength is exceeded. The shear response is defined by cohesion and friction: once the former is exceeded the interface reacts according to Coulomb's behaviour. The simulations are related to the blind predictions, according to the scheduled tests, and the post-dictions, according to the actual testing sequence. The prediction model overestimates displacements and does not catch the actual crack distribution. Therefore, a post-simulation model was implemented, revising the masonry elastic modulus as well as the stiffness and boundary conditions of the supporting piers. Simulations are improved both in terms of displacement predictions and damage mechanism. Finally, the sensitivity to finite-element size, damping ratio and block discretisation was explored. [ABSTRACT FROM AUTHOR]

The assessment of the seismic performance of unreinforced masonry cross-vaults is still a challenge in numerical analysis, due to complex curved geometries and bond patterns, and uncertainties related to the selection of adequate modeling strategies, including but not limited to that of material properties, damping scheme, and unit/joint idealization. This paper presents the results of a collaborative effort to validate, against the shake table test of both unstrengthened and strengthened masonry cross-vault specimens as part of the SERA Project Blind Prediction and Post-diction Competition, various discontinuum-based numerical approaches. First, the geometry of the cross-vault is created using a Python-based computational framework to accurately represent the brick arrangement and the shape of the vault. Then, the geometry is converted into an assemblage of deformable blocks and analyzed using the Distinct Element Method (DEM). An elasto-softening contact model based on fracture energy is implemented in the masonry joints to simulate crushing, tensile, and shear failures. The performance of the proposed strategy, conceived for the unstrengthened configuration of the tested vault specimen and then adapted to include the presence of cementitious repairs, shows satisfactory agreement with both qualitative and quantitative experimental responses, also revealing critical insights and lessons learned through the blind/post-prediction exercise. [ABSTRACT FROM AUTHOR]

Unreinforced stone masonry buildings represent a significant part of the building stock in the areas affected by the recent devastating earthquakes of 6 February 2023 in Turkey. Most of them were built before 2000, and, hence, they are not compliant with current seismic provisions. Severe damage or collapse was observed in a large number of low-rise stone masonry buildings, including many listed as monuments ones. The structural systems of masonry buildings in the historical center of two cities (namely, Gaziantep and Antakya) are presented herein, along with the typical damage observed. The causes of damage are qualitatively interpreted, wherever relevant evidence is available. To this purpose, the observed damage is compared to that occurred in other parts of the world, in structural systems similar to those of the area affected. Furthermore, the detrimental effect of inadequate pre-earthquake interventions is identified, while a critical discussion regarding frequently applied interventions, and the availability of design rules in current Codes and Guidelines, is initiated to pave the way toward efficient measures to be taken for the protection of surviving stone masonry buildings in Turkey and beyond. [ABSTRACT FROM AUTHOR]

The assessment of unreinforced brick masonry structures and infrastructure is a worldwide challenge for the development of resilient urban areas and preservation of historical assets. Among other factors, the estimation of mechanical performance of masonry in existing construction is of importance. However, the characterisation effort does not always satisfy the requirements from structural analyses point of view, i.e. need of elastic, strength and toughness properties, and/or from technical point of view, i.e. use of conventional technical expertise and limited invasiveness. In this respect, the new RILEM Technical Committee CTM aims at promoting the use of tests on masonry cores for the evaluation of compression and shear properties of unreinforced masonry with regular units. Upon a state-of-the-art review, a database of previous experimental test series will be created to identify influencing factors (e.g., core’s geometry, boundary conditions). Selected testing procedures will be compared at various international institutes for a variety of masonry types typically used in existing structures and infrastructure. By comparing results with standardise tests, correction factors will be identified. Eventually, testing guidelines to characterise masonry with core specimens will be defined and shared within the research and engineering community.

Seismic damage due to pounding between adjacent buildings is often observed after significant earthquake events in old urban centers and globally recognized as a potential trigger for complete collapse. This is relevant for unreinforced masonry (URM) structures, which are particularly vulnerable to horizontal actions and seldom feature appropriate seismic detailing. Quantifying pounding damage between dynamically interacting URM buildings, however, is a challenging task, the details of which are difficult to simulate through analytical modeling alone. Numerical simulation of pounding failures, on the other hand, involves impact, separation and re-contact phenomena that often require advanced 3D micro-modeling strategies, often entailing a high computational expense that is not feasible when modeling the coupled seismic response of multiple buildings. To enable simulation of pounding damage in URM structures with relatively low computational cost, this paper investigates the use of a recently developed Macro-Distinct Element Model (M-DEM) approach. To this end, a M-DEM is herein used to simulate the shake-table biaxial pounding response of two dynamically interacting stone building prototypes, tested within the framework of the Seismic Testing of Adjacent Interacting Masonry Structures project sponsored by the Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe. Numerical results were obtained before the experimental test and then subsequently evaluated against the experimental results. The M-DEM predictions satisfactorily reproduced the measured base shear and interface opening, although they underestimated the floor displacement demand, especially in the transversal direction. Building on these encouraging outcomes, a post-test refined M-DEM model was also developed, and results are discussed alongside the lessons learned and proposed enhanced strategies to improve the quality of predictions. [ABSTRACT FROM AUTHOR]

This study presents the numerical simulation of a shake table experimental earthquake campaign of a building aggregate composed of two adjacent unreinforced rubble stone masonry buildings. The experimental testing was performed with the purpose of studying the interaction between a single-storey and a two-storey building connected with a dry joint consisting of a smooth mortared surface. Before performing the experimental testing, various research teams were sent the construction details to participate in a blind prediction competition using different prediction strategies. The approach reported herein to simulate the shake table tests is the discrete element method (DEM) with rigid elements and damage and deformation lumped in inter-block joints that represent the mortar interfaces governed by a non-linear Mohr–Coulomb constitutive laws. The material properties implemented in the model after calibrating using piers shear tests was observed unrealistically stiff. Hence, it was reduced based on the outcome of pushover and eigenvalue analyses. A sequence of earthquakes with incremental acceleration was input to the real and numerical models. Numerical overestimation of damage and displacement was observed probably due to underestimating the damping ratio. Unexpected sliding of the single-storey building occurred at early stages of the simulation. However, the overall behaviour in terms of base shear force, building displacement and damage progression was well captured in the DEM model. The in-plane flexural and rocking mechanism in the two-storey building was correctly simulated. Damage at the interface between the two buildings with separation and pounding was also reasonably well predicted. [ABSTRACT FROM AUTHOR]

To examine structural safety and reliability, an accurate prediction of the variability of structural resistance must first be determined. This may be achieved through extensive physical testing or, more commonly in modern research, synthetic data generation, such as stochastic finite element analyses (SFEAs). Due to the prevalence and versatility of such techniques, and the need for a high level of confidence when performing a safety assessment, an understanding of the accuracy of data derived from SFEAs is essential. In this paper, SFEA models have been developed to predict the responses of 16 unreinforced masonry walls tested in a laboratory under cyclic in-plane lateral loading. Each SFEA has been developed to reflect the as-built conditions of these experimental specimens and focus on predicting the shear capacity of the failure mechanisms that unreinforced masonry shear walls are susceptible to. From the results of these SFEAs, the accuracy (quantified as model error) of this modelling strategy has been estimated by comparing the peak in-plane shear resistances of the laboratory and numerical models. [ABSTRACT FROM AUTHOR]

Unreinforced masonry buildings are highly vulnerable to earthquake damage due to their limited ability to withstand lateral loads, compared to other structures. Therefore, a detailed assessment of the seismic response and resultant damage associated with such buildings becomes necessary. The present study employs machine learning models to effectively predict the seismic response and classify the damage level for a benchmark unreinforced masonry building. In this regard, eight regression-based models, namely, Linear Regression (LR), Stepwise Linear Regression (SLR), Ridge Regression (RR), Support Vector Machine (SVM), Gaussian Process Regression (GPR), Decision Tree (DT), Random Forest (RF), and Neural Networks (NN), were used to predict the building’s responses. Additionally, eight classification-based models, namely, Naïve Bayes (NB), Discriminant Analysis (DA), K-Nearest Neighbours (KNN), Adaptive Boosting (AB), DT, RF, SVM, and NN, were explored for the purpose of categorizing the damage states of the building. The material properties of the masonry and the earthquake intensity were considered as the input parameters. The results from the regression models indicate that the GPR model efficiently predicts the seismic response with larger coefficients of determination and smaller root mean square error values than other models. Among the classification-based models, the RF, AB, and NN models effectively classify the damage states with accuracy levels of 92.9%, 91.1%, and 92.6%, respectively. In conclusion, the overall performance of the non-parametric models, such as GPR, NN, and RF, was found to be better than that of the parametric models.

In unreinforced masonry structures, among the most dangerous events that can occur during earthquakes are the out-of-plane mechanisms. This type of response significantly changes if the wall is restrained by a horizontal element. The collapse, in this case, could take place for slipping/failure of the diaphragm connection or for overturning of the wall, following the formation of a crack at an intermediate height between the base and the top. A specific analytical model is used to capture the complex dynamic behavior of the wall, formed by two stacked rigid bodies (free to rock) with the top one connected to a flexible diaphragm. The model is calibrated using experimental data available in the literature and it is then used to carry out a dynamic parametric analysis. The variation range of relevant parameters refers to the building features surveyed in Emilia-Romagna region, Italy, and their effect on the global response of the system is investigated. Further, the influence of ground motion is considered, using different ground accelerations. The results of the analysis highlight that, for the considered area and return period, the maximum rotations of the system are significant only for large slenderness values. Further, the investigation shows that the diaphragm plays a crucial role in the dynamic response of the system. The stiffness of the diaphragm can significantly reduce the rotations and consequently the risk of overturning. Additionally, the study on the effect of the wall size pointed out how a top spring causes a reverse scale effect. [ABSTRACT FROM AUTHOR]

Unreinforced masonry (URM) buildings in historic urban areas of European countries are generally clustered in an aggregate configuration and are often characterized by façade walls mutually interconnected with adjacent ones. As a result, the seismic performance of buildings in an aggregate configuration can be affected by the mutual interaction between the adjacent units. This interaction, often called the aggregate effect, could significantly influence the level of the seismic vulnerability of URM buildings in aggregate configuration toward in-plane and out-of-plane mechanisms, the latter being the object of the present paper. Traditional methods for assessing the seismic vulnerability of URM buildings neglect the interactions between adjacent buildings, potentially underestimating the actual vulnerability. This study aims to derive fragility curves specific for UMR buildings in aggregate configuration and proposes an innovative methodology that introduces the aggregate effect into an analytical approach, previously developed by the authors for isolated URM buildings. The aggregate effect is modeled by accounting for the friction forces arising among adjacent facades during the development of out-of-plane overturning mechanisms by considering different scenarios, based on how façade walls interact with neighboring structures (e.g., whether they are connected to transverse and/or lateral coplanar ones). The proposed approach is applied to a real case study of an Italian historical center. The obtained results demonstrate that the aggregate effect significantly influences the fragility curves of URM buildings arranged in aggregate configurations. This highlights the importance of considering this effect and the usefulness of the proposed approach for large-scale assessments of seismic vulnerability in historic urban areas, contributing to sustainable disaster risk prevention. [ABSTRACT FROM AUTHOR]

The evaluation of the structural behaviour of a masonry Venetian church with a pointed barrel vault is presented in this paper through an analysis following the necessary steps of a monument study. With a detailed geometric model and material estimation, the finite-element method is used to investigate the influence of specific structural parts of the structure, like masonry buttresses and wall connections, on the structural behaviour. The operational modal analysis is used to identify the structure dynamically. The comparison of the eigenfrequencies, which are estimated by in situ measurements and finite-element modal analysis, is used to perform a model identification. The response spectrum analysis, the static analysis after the subsistence of some parts following strengthening proposals, and the transient analysis of specific seismic excitations are used for the evaluation of the structural behaviour. The purpose of the work is to highlight the need for an interdisciplinary approach to the study of a monumental complex structure, regardless of its scale. The coexistence of structural elements of different stiffnesses, such as vaults, elongated walls, buttresses, transverse walls with pediment and belfry, as well as the concha, affects the mechanical behaviour and the pathology of the structure, which is difficult to study with simplifying models. From the analysis, it is concluded that subsidence problems, combined with seismic actions, lead to the cracking of the masonry, while the existence of buttresses limits the extension of the damage and contributes to the stabilization of the structure. [ABSTRACT FROM AUTHOR]

An experimental and numerical research, aimed at evaluating the in-plane seismic performance of an innovative external steel modular system for the strengthening of load-bearing masonry walls, is currently underway at the EUCENTRE Foundation in Pavia. This paper presents, in particular, the results of the experimental part of this research campaign. Solid clay brick and hollow clay "doppio UNI" masonry typologies, representing common solutions in Italian existing buildings, were considered. After the mechanical characterization of the masonry and of the components of the reinforcement system, cyclic in-plane pseudo-static tests on full-scale specimens were performed in order to investigate the influence of the proposed system on the in-plane response of the walls, compared to the unreinforced conditions. The main seismic parameters of the masonry walls (i.e. elastic stiffness, lateral resistance, displacement capacity and energy dissipation) were assessed depending on the achieved damage mechanism. The proposed reinforcement system provided very promising results, improving the in-plane seismic performance of masonry walls at serviceability and especially at ultimate conditions, with a significant increase of deformation capacity above all in the case of shear mechanisms. [ABSTRACT FROM AUTHOR]

Unreinforced masonry (URM) structure consisting of bricks and mortar suffers severe damage under impact loading, owing to its poor ductility and brittle failure modes. However, natural nacre with a similar structure to that of masonry exhibits superior mechanical properties through the well-designed assembly process. Therefore, a nacre-inspired design method, which hierarchically assembled bricks and engineered cementitious composites (ECC) into novel masonry walls at the macro-scale, was proposed in present study. The variations of the bionic measurements were experimentally explored. Test results demonstrated that the ductility and toughness of the novel masonry structure were dramatically improved by replacing mortar with ECC as horizontal joint and setting artificial local separations. The energy absorption of masonry wall and masonry beam were improved 5.66 times and 8.05 times, respectively. A theoretical frame model for hierarchically-assembled masonry was established, which considered the randomness of masonry and simulated the crack propagation. Finally, a numerical verification was conducted based on the frame model. This study lays the groundwork for applying the nacre-inspired design method in masonry structure to improve its shear properties in terms of ductility and toughness.

Seismic damage shows that the out-of-plane collapse of unreinforced masonry walls is very common. Especially in the teaching buildings, the out-of-plane collapse of the longitudinal load-bearing walls leads to the disproportionate collapse of the building, which results in serious loss of life and property. It is assumed that the in-plane stiffness of the unreinforced masonry floor system is infinite, and the effect of the integral bending of building on the story drift is ignored. The load-displacement relationship for out-of-plane of unreinforced wall under vertical dead load and horizontal seismic load was deduced with the bilinear constitutive relationship of masonry under compression, the second-order effect of vertical load on deformation being considered. The influence of axial compression ratio and the height-thickness ratio of the wall on the failure model and the load-displacement characteristics in the elastic state, ultimate state and collapse state were also studied. A theoretical method for the collapse mechanism and the aseismic design of the unreinforced masonry structure based on displacement was provided. This study has significant implications for the seismic performance design, post earthquake structural reinforcement, and seismic grade evaluation of unreinforced masonry structures.

Masonry structures, particularly those used in developing countries and in historic buildings, typically consist of unreinforced masonry (URM) walls connected by timber or reinforced concrete elements. This study proposes enhancements to the existing two-dimensional (2D) deformable frame model (DFM) to enhance its ability in simulating masonry walls with a specific focus on accurately predicting the transient dynamic response of three-dimensional (3D) masonry structures while maintaining a minimal number of degrees of freedom (DOF). For the modeling of URM walls, the DFM framework employs elastic beams and diagonal struts with nonlinear constitutive behavior. Structural elements, such as reinforced concrete or timber reinforcements, are represented using conventional beam finite elements. This paper first reviewed the current DFM configuration, which primarily addresses the in-plane (IP) behavior of URM structures. It then introduced modifications tailored for 3D structural analysis. The reliability of the enhanced model was validated through two approaches. First, a modal analysis compared the results from the updated DFM with those from a reference 3D model based on cubic finite elements. Second, a shaking table experiment conducted on a half-scale masonry house was simulated. The findings demonstrate that, despite its limited number of DOF, the updated DFM effectively captures the main natural vibration modes. Furthermore, it shows the model’s ability to predict the nonlinear transient dynamic response of 3D masonry structures with accuracy and limited computational time.

Five existing unreinforced masonry buildings, built in different Italian cities in a relatively recent time frame, were selected to study the seismic behaviour of modern existing structures, not designed to withstand seismic actions. The buildings were modelled using an equivalent-frame approach, adopting, and comparing two nonlinear constitutive laws and introducing specific modelling strategies to represent the distinctive features of modern existing URM structures. Nonlinear static analyses were performed to determine capacity and multi-stripe time history analyses to evaluate displacement demand at increasing return periods. Although non-exhaustive, the results show a trend of generally decreasing seismic vulnerability for more recent buildings. [ABSTRACT FROM AUTHOR]

A new macro model for the finite element modeling of unreinforced masonry (URM) exhibiting in-plane nonlinear cyclic behavior is proposed. The ultimate objective is to predict the seismic response of multi-story URM buildings. The macro model enables the modeling of URM shear walls with a limited number of degrees of freedom (DOF) at low computation times. The macro model consists of a deformable elastic frame supported by diagonal struts with nonlinear behavior aiming to capture all dissipative phenomena occurring during seismic events. The nonlinear constitutive behavior of diagonal struts is inspired by models documented in the literature, ensuring a robust foundation for the proposed approach. This paper first provides a comprehensive review of the principal models currently available for URM analysis. It then articulates the rationale behind the development of this new numerical model, aiming to address the limitations encountered in existing methodologies and to offer a simple and fast tool for predicting the seismic behavior of URM buildings. Afterward, the new model is presented and tested with the simulations of two experimental campaigns performed on different URM walls. The comparison between experimental and numerical results shows that with a limited number of DOF and parameters, it is possible to obtain a prediction of the experimental results with satisfying accuracy. [ABSTRACT FROM AUTHOR]

This paper proposes an effective approach to realise circular construction with concrete, and shows Unreinforced Masonry as a foundational building block for it. The paper outlines the importance of circularity in building structures. It specifically focuses on the impact of circular construction with concrete on improving the sustainability of the built environment in a rapidly urbanising world economy. Subsequently, the relevance of principles of structural design and construction of unreinforced masonry to achieve circularity is articulated. Furthermore, the paper presents and summarises recent developments in the field of Unreinforced Concrete Masonry (URCM) including digital design tools to synthesise structurally efficient shapes, and low-waste digital fabrication techniques using lower-embodied-emission materials to realise the designed shapes. The paper exemplifies these using two physically realised, full-scale URCM footbridge prototypes and a commercially available, mass-customisable building floor element, called the Rippmann Floor System (RFS). The paper also outlines the benefits of mainstream, industrial-scale adoption of the design and construction technologies for URCM, including accelerating the pathway to decarbonise the concrete industry. In summary, the paper argues that URCM provides a solution to significantly mitigate the carbon emissions associated with concrete and reduce the use of virgin resources whilst retaining its benefits such as widespread and cheap availability, endurance, fire safety, low maintenance requirements and recyclability. [ABSTRACT FROM AUTHOR]

The demand for advanced nonlinear time‐history and seismic collapse simulations of old unreinforced masonry (URM) constructions to support informed risk evaluation and mitigation plans is rapidly increasing in the structural engineering profession. On one hand, offering cutting‐edge solutions based on the latest advances is challenging for practitioners, given the reduced timeframe usually available for projects and the specialized knowledge required. On the other hand, researchers frequently face difficulties in accessing old buildings and gathering key data required in complex numerical collapse analysis strategies. In this work, a pragmatic approach for evaluation of the earthquake collapse response of vulnerable old URM churches typical of the Northern Netherlands, now exposed to low‐magnitude induced seismicity due to gas extraction, is presented. To bridge the gap between academic and industry applications, an integrated framework is proposed that combines archival and onsite research, code‐based prescriptions, geometrical characterization and simplified discrete element modeling. Main outcomes include the identification of recurrent damage patterns for five old URM churches erected during the 11th, 13th, 14th, and 19th centuries, representative of key traditional multi‐leaf and cavity‐wall structural types, as well as relevant failure mechanisms and collapsed debris distributions for seismic signals of varying intensities. Produced results constitute a solid foundation of data on which to base the design of ad‐hoc retrofits and development of tailored risk assessment models. This study opens a new line of inquiry while discussing practical challenges and research questions which arose, to be of interest to both applied researchers and structural engineering professionals. [ABSTRACT FROM AUTHOR]

The present paper adopts a sophisticated numerical modeling technique using a plasticity-based simplified micro-model method and the extended finite element method for simulating the nonlinear behaviour of unreinforced masonry (URM) walls with different types of sizes and positions of openings. The validity of this model has been proven by comparing the results subjected to a similar loading obtained by the experimental approach. Thereafter, the validated computational model is used to study the behaviour of the 3D URM wall model with different opening percentages. The effect of the position of the openings is also studied. Further, the load–displacement curves are drawn to provide a clear idea about the load-carrying capacity of the same URM walls. The hysteretic behaviour obtained in each model under cyclic loading gives an idea about the energy dissipation capacity of each of the models studied. The same walls are analyzed by strengthening the walls with two cost-effective materials, wire mesh and polypropylene bands. Since the study on lateral behaviour of masonry walls, particularly regarding the effect of area and the position of the opening, is very rarely available, the present detailed study is believed to be helpful in reducing the seismic vulnerability of actual masonry structures, which always have openings with different sizes and positions. [ABSTRACT FROM AUTHOR]

Unreinforced masonry (URM) walls are common load-bearing structural elements in most existing buildings, consisting of masonry units (bricks) and mortar joints. They indicate a highly nonlinear and complex behaviour when subjected to combined compression–shear loading influenced by different factors, such as pre-compression load and boundary conditions, among many others, which makes predicting their structural response challenging. To this end, the present study offers a discontinuum-based modelling strategy based on the discrete element method (DEM) to investigate the in-plane cyclic response of URM panels under different vertical pressures with and without a damp-proof course (DPC) membrane. The adopted modelling strategy represents URM walls as a group of discrete rigid block systems interacting along their boundaries through the contact points. A novel contact constitutive model addressing the elasto-softening stress–displacement behaviour of unit–mortar interfaces and the associated stiffness degradation in tension–compression regimes is adopted within the implemented discontinuum-based modelling framework. The proposed modelling strategy is validated by comparing a recent experimental campaign where the essential data regarding geometrical features, material properties and loading histories are obtained. The results show that while the proposed computational modelling strategy can accurately capture the hysteric response of URM walls without a DPC membrane, it may underestimate the load-carrying capacity of URM walls with a DPC membrane. [ABSTRACT FROM AUTHOR]