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Recent research has underscored the effectiveness of engineered cementitious composites (ECC) in retrofitting unreinforced masonry (URM) structures. The retrofitting method of embedding ECC in the bed mortar joints is suitable for strengthening historic masonry buildings because the ECC can be concealed within the mortar joints. This study introduces an experimental campaign aimed at understanding the effects of this strengthening method on the in-plane seismic performance of URM walls. Four half-scale masonry walls, one of them unreinforced and the remaining three reinforced with ECC, were built and tested under in-plane cyclic loads. From the test results, it was found that the proposed retrofitting method can mitigate brittle diagonal shear damage and improve the integrity of the masonry walls. Furthermore, the results demonstrated that ECC reinforcement effectively increased the seismic behavior of URM walls in terms of shear bearing capacity, ductile behavior, stiffness degradation, and energy dissipation capacity. The ductility coefficient is defined as the ratio of ultimate displacement to yield displacement. The maximum lateral load and ductility coefficient of the reinforced masonry walls increased by a maximum of 26.08 and 25.77%, respectively, in comparison with the URM wall. Additionally, the lateral bearing capacity of both unreinforced and reinforced specimens was assessed using theoretical models. The results showed that the theoretical model could be used to predict the maximum lateral loads of the specimens, with the error of the calculated and tested maximum lateral loads being within 5%. The hysteresis curves of ECC-reinforced walls were predicted using an idealized trilinear model and a modified Clough model, and the applicability of the hysteresis model was assessed by comparing the force demand history and energy dissipation history of the computed and experimental hysteresis curves. [ABSTRACT FROM AUTHOR]

This study assessed the seismic damage to historical masonry towers using a three-dimensional finite element (FE) numerical model. The FE model was validated by comparing the dynamic characteristics and seismic analysis results with experimental data obtained using shaking table tests conducted on a 1/8 scaled tower model. Based on this analysis, a numerical analysis model of the damaged ancient brick masonry tower was established by introducing factors such as initial cracks and inclination, and the damage FE model was validated using experimental data provided by the shaking table tests. Subsequently, the damage index of the wall components were obtained using the modified Park–Ang damage model; these were used to obtain the damage indices of the historical tower floors, which were further used to obtain the overall damage indices of the historical tower. Furthermore, the performance levels of historical towers were proposed, and the damage indices at different performance levels were quantified using various parameters. Finally, the damage to the historical tower model in the shaking table test was analyzed based on the various quantitative results. [ABSTRACT FROM AUTHOR]

Assessing the seismic vulnerability of existing buildings is an essential task for the management of earthquake disasters. For this purpose, the seismic behaviour of buildings is usually determined under the assumption of isolated conditions, although aggregate structures are one of the most common typologies found in urban centres. This study aims to investigate the nonlinear static behaviour of aggregate dwellings consisting of grouted reinforced concrete block configurations commonly observed in San José, Costa Rica. This research investigates the use of several strategies to model connections between adjacent buildings which are typically found in modern building practises in this country. The methodology used here to analyse the seismic behaviour of isolated and row-aggregated dwellings reveals significant differences in their response under seismic loads, especially when acting perpendicular to the aggregate. The study reveals that the type of interaction considered between adjacent buildings has a very important impact on the seismic capacity and failure mechanisms of the aggregated structures. This procedure can also be applied to the vulnerability assessment and retrofit of existing aggregates. [ABSTRACT FROM AUTHOR]

This study presents the analysis of the methodology of a seismic exposure model in Guatemala City. In the last years, progress in the investigation of regional seismic hazards has revealed the need to study the vulnerability of buildings in Central America. In addition, in recent years there have been earthquakes of moderate magnitude in Guatemala causing damage in some areas of the country. An accurate exposure model and updated threat scenarios are essential for a detailed vulnerability study. This exposure study for Guatemala City reveals the presence of structural typologies that are very vulnerable to earthquakes: adobe and simple masonry. Similarly, the study reveals the majority presence of reinforced masonry and the growing construction of reinforced concrete buildings. The characteristic of this model is the use of historical aerial photographs of Guatemala City to determine the relationship between constructive typologies. The lack of exposure studies in the country has prevented the creation of policies to reduce vulnerability to a catastrophe like the earthquake in 1976. The analysis and methodology presented in this study are the preliminary step in formulating seismic risk prevention and mitigation plans in Guatemala City; knowledge of the city's exposure contributes to making subsequent actions more effective. Based on the results obtained, matrices are proposed according to the age and material of the buildings for the typological classification of the structures. [ABSTRACT FROM AUTHOR]

The damage level (DL) is a fundamental metric in earthquake engineering and is particularly effective for multiple purposes, such as correlating structural damage to consequences and losses (e.g. economic, casualties, etc.) as well as to physical and mechanical variables quantifiable from both experimental and numerical tests. Despite the relevance of the topic, the conversion of complex information on the damage spreading over a 3D building into a synthetic DL remains an open issue for which there are currently no agreed-upon scientific criteria in the literature. Within this context, the study focuses on unreinforced masonry (URM) buildings by providing an analytical multi-scale approach that integrates structural damage at the panel-scale and macro-element size (where the macro-element is intended as an assemblage of components, like vertical walls or diaphragms). The approach is specifically conceived to be applied consistently to both observed and numerically simulated damage. As a result, the method is particularly effective for supporting the validation of numerical models or synthetically interpreting the huge amount of results from nonlinear analyses as much as feasible using an objective basis. The paper proposes a comparison of DL interpretation arising from other approaches in the current literature, highlighting their pros and cons. The effectiveness of the proposed procedure is then assessed using four URM case studies, all of which exhibited primarily a 'box-like behaviour'. They were specifically chosen based on the extremely detailed documentation available for both the damage and geometric/mechanical features of the buildings as well as aiming to reduce the uncertainty in the seismic input, making them ideal candidates also for validation purposes. To this end, the applicability of the procedure also to the damage simulated by nonlinear dynamic analyses was proven by adopting equivalent frame models of the case studies, developed and calibrated in previous researches. Definitely, the results encourage the adoption of the proposed procedure to interpret as analytically as possible the real damage that occurred on URM building, when accurate damage observations from field surveys are available, as well as that coming from numerical simulations. [ABSTRACT FROM AUTHOR]

Two strong earthquakes hit Thessaly region on March 3rd, 2021 (Mw = 6.3) and on March 4th, 2021 (Mw = 6.1). The epicentres of the earthquakes were located at approximately 23 and 29 km respectively NW of Larissa, one of the most populous cities in Greece. Several aftershocks followed thereafter. Although no injuries were recorded, several structures suffered significant damage close to the epicentre, while some others collapsed. Approximately 300 residents of the village of Damasi were transferred to temporary settlements and tents. The event occurred during the COVID19 lockdown and created significant stress and disruption to residents. This paper focuses on the earthquake swarm itself as well as the damages observed in residential buildings, schools, and churches in the earthquake-stricken region. The earthquakes mainly impacted low-rise domestic masonry buildings, while the more modern reinforced concrete structures built following the recent seismic regulations were almost unaffected. The typology of buildings in the region, together with photographs demonstrating the extent of damage are presented herein. Despite the rather satisfactory performance of modern buildings in recent earthquakes in Greece, the preliminary investigations from the Thessaly Earthquakes showed that there is still a significant level of vulnerability in existing masonry building stock constructed using traditional methods and materials. This issue could re-emerge in future earthquakes striking other rural areas of Greece, something that needs to be addressed systematically in the future. [ABSTRACT FROM AUTHOR]

This paper proposes a multi-platform simulation method for the seismic performance assessment of masonry infilled reinforced concrete (RC) frames, especially for those that, due to inadequate reinforcing details, tend to undergo shear failure during an earthquake. The multi-platform method is based on a micro–macro modeling approach in which a detailed finite element model of the RC frame is incorporated with a strut model of the infill wall. It exploits the strut model to increase its computational efficiency and the finite element model based on the modified compression field theory to capture the nonlinear behaviour of the RC frame. The proposed method is validated against previously tested frames subjected to lateral loads, and its advantages over the conventional strut models are demonstrated through both quasi-static and dynamic analyses. [ABSTRACT FROM AUTHOR]

This paper provides a comphrensive review of the critical aspects of nonlinear modeling for evaluating the seismic response of masonry structures, emphasizing the issues relevant to engineering practice. Currently, the specialized technical community shares the opinion that, for a performance-based approach, numerical models are the only tools sufficiently effective to support the seismic assessment of existing buildings. However, their potential often falls short when attempting to accurately describe the behavior of masonry structures. In fact, these structures feature highly complex architectural configurations, different masonry types, and various structural solutions, meaning that extra care is required in numerical modeling. This is especially true when the modelers do not have a solid background in the software chosen and may not be practiced using the vast variety of options offered by the software houses. They are often unaware of the consequences that questionable modeling choices may have on the results obtained by the models. These extremely complex topics are treated in the paper from an engineering practice perspective, providing an in-depth overview of the challenging issues related to the use of different modeling strategies. The paper covers strategies ranging from the Equivalent Frame approach (widely used in common engineering practice) to more refined techniques like 2D and 3D Finite Element procedures based on continuous, discrete, and micro-mechanical approaches. Critical aspects in the modeling of both in- and out-of-plane responses of masonry, as well as the critical issues in wall-to-wall connections and diaphragm roles are investigated. All the examined issues are clarified through numerical examples highlighting also how a consistent and integrated use of different procedures may be beneficial. Finally, some of most relevant challenging issues concerning the use of numerical models in seismic assessment with the nonlinear static approach are presented and discussed. [ABSTRACT FROM AUTHOR]

The paper presents the comparison of the results of nonlinear static analyses carried out using six software packages (SWs) available at professional level and operating in the field of the equivalent frame (EF) approach on a model representative of a complex masonry building. The structure is inspired by the school "P. Capuzi" in Visso (MC, Italy), proposed as one of the benchmark structures in the "URM nonlinear modelling—Benchmark project" funded by the Italian Department of Civil Protection within the context of the ReLUIS projects. The 2-stories building is characterized by an irregular T-shaped plan and load-bearing walls consisting of two-leaf stone masonry with a rather regular bond scheme. The school was severely damaged by the seismic sequence that hit Central Italy in 2016/2017 and essentially exhibited a global in-plane box-type response, with a clear evidence of cracks concentrated in piers and spandrels. The availability of an accurate survey of the crack extension represents a precious and rare reference to firstly address in the paper the rules to be adopted in the EF models for the definition of the structural elements geometry. Then, the comparison of results is made with a twofold aim: firstly, by setting the models adopting shared and consistent modelling assumptions across the SWs; secondly, by investigating the sensitivity of the seismic response to some common epistemic and modelling uncertainties (namely: the adoption of various EF idealization rules for walls, the out-of-plane contribution of piers, the flange effect). In both cases, results are post-processed to define reference values of the achievable dispersion. The comparison is carried out in relation to a wide set of parameters, namely: global parameters (e.g. dynamic properties, pushover curves and equivalent bilinear curves); synthetic parameters of the structural safety (i.e. the maximum acceleration compatible with the ultimate limit state); the damage pattern simulated by SWs. [ABSTRACT FROM AUTHOR]

Recent technological advances have enabled earthquake engineering researchers to develop numerical models of increasing complexity, capable of duly reproducing even the smallest structural detail. In the case of unreinforced masonry (URM) structures, however, because of their discrete and heterogeneous nature, computational performance tends to decrease exponentially as a function of the adopted refinement level, thus confining the applicability of advanced micro-models, according to which each masonry unit is typically modelled separately, to reduced-scale problems. To enable their use at a building scale, and benefit from considering simultaneously out-of-plane failures, local wall-diaphragm interaction and collapses, researchers often need to decrease the level of detail of specific members or sub-structures. In the current literature, however, the influence of the abovementioned simplifications on the quality of micro-modelling predictions has been only marginally investigated so far, while code-based guidelines are missing. To start addressing such knowledge gap, the dynamic response of a shake-table-tested full-scale URM building specimen has been simulated in this work using a very detailed micro-model, and the results obtained were then compared with those of nominally identical models in which, however, the idealisation of some specific structural elements has been purposely simplified. Aimed at further extending the impact of this study, pushover analyses were also performed using the same models. Preliminary outcomes, which may serve as a reference to develop more informed, effective and targeted multi-scale micro-modelling strategies in the future, indicate that: (i) maximum base shear predictions tend to be less impacted by the introduction of modelling simplifications, (ii) despite requiring more labour, the explicit representation of the brickwork pattern generally led to better results in terms of predicted damage propagation, failure mechanisms and displacement capacity, (iii) using equivalent membranes, as opposed to modelling each component of timber diaphragms, provided acceptable results, making it a plausible alternative for practical applications of micro-modelling approaches. [ABSTRACT FROM AUTHOR]

The seismic response of existing masonry structures is strongly influenced by floor and roof in-plane properties. A strengthening intervention is often needed for traditional timber floors to overcome their low in-plane stiffness and to preserve historical buildings. In this study, the effects of unreinforced and reinforced timber floors on the seismic behaviour of an existing listed masonry building are investigated with dynamic non-linear analyses by means of the Discrete Element Method (DEM). With this approach, the failure processes and collapse sequences of masonry structures can be captured in detail. A previously developed model of the floor cyclic behaviour, based on experimental data, is applied herein to DEM models of the masonry building. Different seismic ground accelerations, different floor types and different floor-to-wall connections are considered. The results highlight the effectiveness of the analysed floor strengthening solution in reducing the out-of-plane displacements of masonry walls. With adequate connections, the reinforced floor is able to transfer the seismic forces to the shear-resistant walls up to the shear-sliding collapse of the structural sidewalls. A comparison with the ideal rigid diaphragm case confirms the good performance of the strengthened floors. The small observed out-of-plane displacements are compatible with the masonry wall capacity, and the reinforced floor hysteretic cycles contribute to dissipate part of the input energy. Moreover, different designs of the connections can also cap the transferred seismic forces to an acceptable level for shear-resistant walls. [ABSTRACT FROM AUTHOR]

The seismic assessment of existing masonry infilled reinforced concrete (RC) building portfolios is a highly relevant issue in Italy and other Mediterranean countries, particularly in regions where a large part of the built environment was not designed according to modern seismic codes. In the past, masonry infills were generally considered as non-structural elements and were not accounted for in the design process. However, the results of experimental tests and past earthquake evidence demonstrated the influence of masonry infills on the global and local behaviour of RC buildings. Furthermore, the acknowledgment of different construction practices points out the significant variability affecting the masonry infills in terms of material properties, thickness, presence of openings and manufacturing techniques. This paper deals with the large-scale performance analysis of existing masonry infilled RC building portfolios accounting for the uncertainty related to the variability in the mechanical properties and the modelling of masonry infills. To accomplish this goal, a fully integrated building stock, representative of masonry infilled RC buildings designed according to the Italian codes in force between 1960 and 1980, was developed, using a simulated design approach. Statistical data and results of experimental tests were used to identify the main masonry infill typologies adopted in the Italian context. Detailed numerical models, whose prediction capability was appraised through the results of cyclic quasi-static tests, were developed to estimate the lateral response of the analysed RC buildings. Different response parameters, which can be easily implemented in seismic risk assessment frameworks, were considered and quantified, at the portfolio level, to understand the uncertainty propagation and impact of the masonry infills' variability on the expected performance of existing RC buildings. The results demonstrated that the variability related to the definition and modelling of the masonry infills induces significant dispersion, with respect to the mean, on the lateral response of different classes of buildings within a given portfolio. Moreover, the provided parameters for multi-linear idealised capacity curves can be used in simplified seismic fragility and risk models for existing buildings, including a proper estimate of the associated uncertainty, leading to a more accurate quantification of economic losses. [ABSTRACT FROM AUTHOR]

The current research focuses on a numerical and analytical study aimed at investigating the efficiency of a steel-based reinforcement system suitable for existing masonry walls. The application of such a retrofitting technique, which consists of glued thin steel grids applied on both faces of a masonry panel, is reversible, cheap and easy to be executed and appears to be suitable especially for buildings with concrete slab or inter-stories beams to which the steel elements could be anchored. The study is based on a reference experimental test carried out at the "Politehnica" University of Timisoara (Romania), within the European FP6 project PROHITECH. The reference test provided the application of a constant vertical compression and cyclic horizontal displacements to an unreinforced brick-cement mortar wall in full-scale (1500 × 1500 × 250 mm), to which was conferred a double-fixed constraint condition. Based on the experimental evidences, a reference numerical model has been implemented in ABAQUS, by adopting a plastic-damage material and a macro-element approach for the masonry modelling. Hence, in order to determine a design criterion of the studied system, a comparison with the analytical formulations available in the current Italian and European codes for the unreinforced configuration is presented in this study. Then, a wide parametric study on the investigated retrofitting technique has been carried out by varying thickness and spacing of steel grid elements, as well as the geometrical ratio of the panel (height/length). On the basis of the numerical results, a capacity formulation has been proposed, which takes into account the steel distribution in the masonry panel. The obtained outcomes revealed that the strength increase achievable by adopting the studied reinforcement system could be compared to the efficiency of a reinforced masonry wall of new construction and it is strongly influenced by the geometrical ratio of the wall, as well as the steel distribution. [ABSTRACT FROM AUTHOR]

Past earthquakes have repeatedly shown that damage to masonry infills can produce large economic losses and even jeopardize human lives. Nevertheless, in current design practice masonry infills are ignored, while available macro-models for nonlinear analysis focus the attention on the In-Plane (IP) behavior of masonry infills only, while neglecting the Out-Of-Plane (OOP) collapse mechanism. The main objective of this study is to investigate the seismic performance of RC frame buildings accounting for the interaction between IP and OOP behavior of masonry infills. To this end, a suitable nonlinear model, able to capture the IP stiffness and strength reduction due to the OOP displacement demand (and vice versa) is implemented. The selected model incorporates a routine that removes infills from the structural model when either IP or OOP collapse occurs. Different building models, representative of typical residential buildings, realized in Italy (and other European countries) from 50's to 90's, are examined through nonlinear response-time history analysis at different earthquake intensity levels, with return period ranging from 30 to 5000 years. Two alternative infill configurations (single layer and double layer with inner cavity) are considered, in accordance with the construction practice of the time. The comparison between the models with and without IP/OOP interaction points out the relevance of the OOP behavior towards an accurate evaluation of the seismic performance of RC frame buildings. A set of fragility curves is tentatively proposed, for different building performance levels, ranging from immediate occupancy to life safety. [ABSTRACT FROM AUTHOR]

Masonry walls are particularly vulnerable against out-of-plane seismic actions. Steel tie-bars and crowing beams in reinforced masonry can prevent their overturning, but collapse may take place also by bending, leaf separation or disaggregation. Textile Reinforced Mortar (TRM) composites, comprising high strength fabrics and inorganic matrices, can be applied to effectively improve the seismic capacity of masonry load-bearing walls and infill panels. Nevertheless, a deeper knowledge on the dynamic response and ultimate capacity of retrofitted walls still needs to be gained before TRM systems can be confidently used in engineering practice. This work describes a shake table test carried out on two full-scale wall specimens, one made of regular tuff blocks and one of two leaves of rubble stones, subjected to seismic out-of-plane vertical bending. The walls were tested unreinforced, repaired and strengthened with TRMs and tested again. A unidirectional textile of ultra high tensile strength steel was used on the tuff wall, whereas a bidirectional basalt mesh was applied over the entire surface of the stone wall, with the addition of transversal steel connectors. The responses of the specimens before and after retrofitting are compared to show the improvement of acceleration and displacement capacity entailed by TRM retrofitting and the modification of deflection profiles, failure modes, damage development and dynamic properties. Test outcomes prove the effectiveness of TRM composites for the protection of existing masonry structures, including architectural heritage, in earthquake prone areas and provide information on the reliability of analytical predictions for seismic assessment. [ABSTRACT FROM AUTHOR]

Assessing the mechanical properties of irregular stone masonry in historic buildings is a challenging task, as it is highly heterogeneous with many uncertainties involved. In-situ Non-Destructive (NDT) or Minor Destructive (MDT) testing can be implemented to evaluate the mechanical properties; however, this is often difficult due to restrictions by legislation, policy and guideline that protects the heritage of listed buildings. To comprehend the mechanical properties of stone masonry, an experimental database comprising the mechanical properties of stone masonry determined through axial compression, double flat-jack and diagonal compression tests was established and analysed in this study. The stone masonry assemblages in the database were categorised using the Italian building code and Masonry Quality Index (MQI) method. The experimental database includes compressive and shear strengths, Young’s and shear moduli of different stone masonry types before and after reinforcement. The mechanical properties were appraised to verify their correlations among them, and to assess the effectiveness of both traditional (grout injections, steel mesh cement coating, etc.) and innovative (Reticulatus technique and composite materials) retrofitting methods. The database and analyses presented in this study would enable to further understand the mechanical properties of traditional stone masonry and select appropriate strengthening techniques. [ABSTRACT FROM AUTHOR]

It is generally known that reinforced concrete frame structures with unreinforced masonry infills frequently suffer severe damage when subjected to earthquake loading. Recent earthquakes show that the damage occurs to both older buildings and new seismically designed buildings. This is somehow surprising as this construction type has been the subject of intensive research projects for decades and simplified verification concepts are available in standards. However, these concepts are based on the separate verification of in-plane and out-of-plane loading although the importance of the design for combined loading conditions is already known. This situation was the reason to perform comprehensive investigations of the seismic behaviour of this traditional construction type for separate and combined in-plane and out-of-plane loading within the framework of the collaborative European research project INSYSME (Innovative systems for earthquake resistant masonry buildings in reinforced concrete buildings). These investigations are helpful to develop innovative approaches to improve the seismic behaviour of infilled frames. This article presents the fundamental project results of experimental investigations on reinforced concrete frames filled with high thermal insulating clay bricks under separate, sequential and combined in- and out-of-plane loading. The test results clearly illustrate that the load-bearing capacity severely depends on the boundary conditions in the connection area between the infill and the frame. [ABSTRACT FROM AUTHOR]

Many strengthening techniques for masonry structures were thoroughly investigated in several researches. The in plane shear behaviour of an ancient full-scale masonry wall, characterized by an opening that is strengthened by the lintel in the arch form, retrofitted with an innovative system constituted by three-dimensional pre-tensioned stainless steel ribbons, was previously tested. In this paper the double flat-jack test results were analyzed and design of the retrofitting system was detailed. The collapse mechanisms in terms of flexural bending and shear, both sliding and diagonal tension, as function of the compression stress level were taken into account. The arrangement of the ribbons was established on the base of an equivalent frame model of the masonry wall, investigating the flexural and shear strength of each element (piers and spandrel). Moreover, the numerical results of the response behaviour modelling of the unreinforced and reinforced masonry wall were presented. The analytical modelling of the wall was accomplished suitably applying the methods of the disturbed stress field model, successfully used for reinforced concrete elements. The numerical results provided a good prediction of the response behaviour of the wall, both in terms of load-displacement curve and crack pattern at failure. [ABSTRACT FROM AUTHOR]

In this study, the efficiency of conventional shotcrete technique for strengthening of Un-Reinforced Masonry (URM) walls was shown using an experimental program. In addition, in this program the possible benefit of using anchors for connecting the shotcrete reinforcement layer to the R/C foundation was studied. The experimental program consisted of testing five full scale specimens with two different height-to-length aspect ratios and so different failure modes, under in-plane cyclic loading conditions. Two specimens were tested as reference and others were strengthened on a single-face using shotcrete layer. According to the results, strengthening of URM walls using traditional shotcrete approach created a completely stiff panel and prevented the formation of cracks. The failure mode in both reference and strengthened short length walls was rocking and the shotcrete layer could increase the strength capacity, energy dissipation, and stiffness of wall due to yielding and rupture of steel bars anchored to the foundation. On the other hand, in strengthened long length walls, shotcrete layer increased the shear sliding capacity with no or small increasing in their rocking capacity. Therefore, the failure mode of strengthened walls converted from shear sliding to rocking, even in the specimen with anchorage system. The distributed type of anchorage system could not improve the strength capacity of long length wall. Anchorage system was able to improve the out-of-plane performance of strengthened walls. [ABSTRACT FROM AUTHOR]

As part of an ongoing research project into the seismic response of partially grouted reinforced masonry (PG-RM) walls, this article presents the analysis of the experimental results of eight full-scale walls that were tested in laboratory under cyclic lateral loading. All walls tested were constructed using multi-perforated clay bricks and horizontally reinforced with ladder-type bed-joint reinforcement. Three design parameters were investigated in this research: wall aspect ratio, axial load level, and horizontal reinforcement ratio. The combined effect of these variables on shear response of the walls tested is analyzed and discussed. In addition, the accuracy of four shear expressions available in the literature is assessed against the experimental results obtained. The study has confirmed that a rise in the horizontal reinforcement ratio may lead to an increase in lateral capacity of PG-RM walls, although this effect would be more remarkable for square and slender walls. The results obtained also suggest that the influence of axial load level becomes more relevant as the aspect ratio decreases. In addition, moderate values of displacement ductility, ranging from 2.5 to 5.5, were estimated from a bilinear idealization. At the level of maximum lateral force, the average drift level for all walls tested in this experimental program ranged between 0.2 and 0.62%. Finally, the research also confirms the need to review the shear expressions currently available for the design and assessment of this type of walls. [ABSTRACT FROM AUTHOR]

Clay-brick unreinforced masonry (URM) chimneys are a common architectural feature of vintage domestic and commercial URM and timber-framed buildings widely encountered worldwide. URM chimneys include a cantilevered appendage above the roofline that during earthquakes-induced shaking is susceptible to significant damage and collapse, which can result in fatalities, injuries, and property damage. To mitigate this risk, many vintage URM chimneys are removed, braced, or eventually replaced with modern alternatives. The earthquake performance of 15,400 URM chimneys damaged during the 2010/2011 Canterbury earthquake sequence was investigated using a photographic database and insurance claims data. The widespread damage and failure of a large proportion of retrofitted chimneys was the impetus for an experimental shake-table testing campaign that was undertaken to assess the performance of five prototypical URM chimneys in their as-built and retrofitted conditions. Cost-effective retrofit techniques with low aesthetic impact, including the use of near surface mounted carbon-fibre reinforced polymer strips and post-tensioning, were investigated. Tested chimneys were constructed to replicate the most commonly encountered geometric characteristics and construction details collected during an in-field pilot survey of 351 undamaged vintage URM chimneys. [ABSTRACT FROM AUTHOR]

Regional seismic damage prediction is an important approach to discover the weakness of a city so as to effectively mitigate seismic losses. A major proportion of regional seismic losses is caused by masonry buildings. As a result, an accurate prediction of the regional seismic damage to masonry buildings has significant engineering and scientific values. Various parameters of the computational models for regional seismic damage predictions usually involve considerable uncertainty, especially for masonry buildings. Therefore, a parametric sensitivity analysis for the regional seismic damage prediction of reinforced masonry buildings is performed in some detail in this study. Damage to this kind of buildings is predicted through nonlinear time-history analysis using the multiple-degree-of-freedom shear model, which can better represent the features of different buildings and ground motions. In the sensitivity analysis, two widely used methods, the first-order second-moment (FOSM) method and the Monte Carlo method, are adopted and their prediction results are compared. The outcomes of this study indicate that the uncertainty of parameters has a small influence on the analysis results when the total number of regional buildings is large. However the uncertainty cannot be neglected for individual building analysis. In addition, the FOSM method, which is more time-saving, can achieve a similar level of prediction as the Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

Due to proofing error affiliations of co-author M. Rossi was not correctly captured and needs to be read as the work was produced when author was affiliated to the University of Genova. The online version of the original article can be found at https://doi.org/10.1007/s10518-021-01280-0. [Extracted from the article]

The efficiency of strengthening traditionally built three-leaf stone masonry walls with different types of composite reinforced coating has been investigated. Glass fibre grid in single component fibre reinforced mortar and glass fibre fabric in epoxy resin matrix were used as coating materials. Four different coating types have been applied, with coating placed on one or both sides of the walls, anchored or not anchored to the masonry at the corners of the walls. Ten walls have been tested by subjecting them to cyclic shear loading at constant precompression, among them two walls in the original state as the control specimens. Four walls have been first tested up to the occurrence of the first significant damage, strengthened and then re-tested up to collapse, whereas four walls have been strengthened undamaged and tested up to collapse. All walls failed in shear. Significant increase in lateral resistance with regard to control walls was observed in all cases, up to 2.5-4.0-times the resistance of the control walls. The degree of improvement did not depend on the type of coating but on the technology of application. Although the coating increased the rigidity of the walls, displacement and energy dissipation capacities have been also improved. [ABSTRACT FROM AUTHOR]

Many older unreinforced masonry (URM) buildings feature timber floors and solid brick masonry. Simple equivalent frame models can help predicting the expected failure mechanism and estimating the strength of a URM wall. When modelling a URM wall with an equivalent frame model rather than, for example, a more detailed simplified micro-model, the strengths of the piers and spandrels need to be estimated from mechanical or empirical models. Such models are readily available for URM piers, which have been tested in many different configurations. On the contrary, only few models for spandrel strength have been developed. This paper reviews these models, discusses their merits, faults and compares the predicted strength values to the results of recent experimental tests on masonry spandrels. Based on this assessment, the paper outlines recommendations for a new set of strength equations for masonry spandrels. [ABSTRACT FROM AUTHOR]