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Understanding the out‐of‐plane behavior of unreinforced masonry walls is crucial in seismic assessment of existing buildings. Here, the dynamic response of a vertical spanning strip wall, connected to a flexible diaphragm at the top, is investigated. Despite the simplicity of the model, two rocking rigid bodies elastically restrained at the top, the dynamic response is highly nonlinear. This behavior is due to different phenomena: when in motion the system may assume different configurations, with the transition between them due either to impacts or crack opening caused by ground acceleration. An analytical model capable to capture the complex dynamic response of the system is implemented. The equations of motion are first derived, using variational methods, then the events that the system can undergo during motion are studied. Finally, in order to show the potential of the model, some numerical exemplifications are presented applying an earthquake record and a sine pulse to the system. [ABSTRACT FROM AUTHOR]

Recent studies have shown how the variability of material properties affects the nonlinear behaviour of unreinforced masonry (URM) walls. To preserve the historical built heritage, variations in structural capacity of URM buildings associated to aging and deterioration of masonry should be quickly predicted, by integrating with structural health monitoring and risk management. In this study, relationships between structural capacity features and material properties are numerically investigated for single walls, based on a structural modelling strategy that was experimentally validated on full-scale URM walls. The paper proposes an evaluation of the effects of degradation of material properties on the macroscopic descriptors of single masonry walls, such as peak strength and stiffness, also considering the uncertainties in the estimate of those properties. The authors do not attempt to model the physical processes of material aging with time, but assume certain levels of material degradation and investigate their effects on the structural response and capacity. Force–displacement curves and failure modes are associated with the overall nonlinear response of masonry walls due to progressive deterioration of material properties. Regression models are then proposed to predict variations in the peak load-bearing capacity and in -plane lateral stiffness when the mechanical properties of the constituents changed. [ABSTRACT FROM AUTHOR]

Historic masonry buildings often require structural repair or retrofit to attain a satisfactory level of seismic resistance. This paper analyses the effect of externally bonded fibre-reinforced polymer (FRP) retrofitting systems on the global seismic response of such buildings in order to achieve the fundamental code-based requirements that refer to the structure's state of damage for a specified limit state. As a case study, a three-storey historic unreinforced masonry (URM) building was selected. The first part of the paper presents an FRP design procedure for determining which vertical structural elements should be retrofitted and to what extent. As a result, six different FRP retrofitting layouts have been selected and analysed with the aid of non-linear static analyses in the second part of the paper. The paper concludes with a cost-feasibility study by introducing a cost-effectiveness index for FRP reinforcement that identifies the effectiveness of an FRP layout by accounting for the amount of retrofitting material used and comparing it with its effectiveness in improving the global seismic resistance. [ABSTRACT FROM AUTHOR]

Plane‐stress and shell macromodels are often preferred to analyze masonry structures because of their numerical efficiency. However, they often misestimate the hysteretic behavior of the structures. Additionally, due to the nature of smeared cracks, the cracks may be diffused. This article proposes a new orthotropic model, which focuses on the cyclic, nonlinear behavior of brick masonry structures. The model adopts a total‐strain based rotating crack approach. It describes tensile and compressive failure in the rotating principal directions, while including indirectly shear failure through an internal iterative algorithm. Two distinctions are made regarding the tensile postpeak and unloading/reloading behavior based on the crack orientation at crack initiation: a steep softening branch and secant unloading are adopted when the crack angle corresponds to in‐plane flexural failure, and a softening branch and bilinear unloading are adopted when the crack angle corresponds to diagonal shear failure. Bilinear unloading/reloading is adopted in compression, resulting in a cyclic behavior resembling shear. The constitutive model was implemented in a finite element software and validated against experimental results. The numerical simulations reproduced well the experimental outcomes in terms of envelope load‐displacement curve and hysteretic behavior, while simultaneously they resulted in localized damage, representative of the experimental crack patterns. [ABSTRACT FROM AUTHOR]

The paper presents a seismic safety assessment of unreinforced masonry (URM) building using two approaches. The first approach uses the 'Pier Analysis' method, based on the concept of equivalent lateral stiffness, where in-plane and out-of-plane actions are considered independently. The second approach is developed with the program SAP2000, where the linear response is evaluated using continuum 'finite element modelling' (FEM). Both methods are compared to evaluate the safety of wall piers and the differences in the outcomes under combined gravitational and lateral seismic forces. The analysis results showed that few wall elements are unsafe in in-plane and out-of-plane tension. It is also observed that the pier analysis method is conservative compared to FEM, but can be used as a simplified and quick tool in design offices for safety assessment, with reasonable accuracy. To safeguard the URM wall piers under lateral loads, a retrofitting technique is adopted by providing vertical and horizontal belts called splints and bandages, respectively, using welded wire mesh (WWM) reinforcement. The study using the 'Pier Analysis' shows that the lateral load capacity of unsafe URM piers can be enhanced up to 3.67 times and made safe using the applied retrofitting technique. Further, the retrofitting design methodology and recommendations for application procedures to on-site URM buildings are discussed in detail. [ABSTRACT FROM AUTHOR]

It is well established that unreinforced masonry (URM) buildings develop damage‐forming collapse mechanisms during high‐intensity earthquakes, with these mechanisms exhibiting large rocking displacements before collapsing. The Discrete Element Method (DEM) of analysis can realistically capture phenomena that involve large movements of elements, resulting in the technique being ideal for simulating the collapse of URM building elements. Consequently, extensive research using DEM to analyse the seismic response of URM buildings and building components has recently been published. However, the variety of reported damping approaches that have apparently led to DEM results that successfully replicate physical observations underscores the need for consistent guidance related to the assignment of damping factors. The Rayleigh damping distribution model implemented in the DEM software 3DEC was used to study the differences between mass proportional (MP) and stiffness proportional (SP) damping configurations. After reviewing phenomena that need to be damped and previous works where damping was implemented, the capabilities and drawbacks of the time‐efficient MP damping configuration were studied and the results compared to simulations with SP damping. When considering numerical simulations that incorporated MP damping and led to results that were seemingly well‐matched to experimental tests, it was found that the apparent robustness of decisions pertaining to the adopted input parameters was deceptive in most cases. Consequently, SP damping was recommended for all DEM rocking simulations, even though MP damping could be used with satisfactory accuracy in certain situations discussed herein. A pragmatic relationship between both damping strategies was proposed. [ABSTRACT FROM AUTHOR]

In the seismic analysis of unreinforced masonry (URM) structures, the modeling of out‐of‐plane (OOP) modes and their mechanical interaction with in‐plane (IP) loaded components are typically neglected when using simplified numerical methods. Although this may result in unconservative predictions, the high computational expense entailed by more refined approaches is often prohibitive for applied researchers and practitioners. To overcome these limitations, the demonstrated capabilities of a recently developed low‐cost Macro‐Distinct Element Model (M‐DEM) to simulate IP and OOP modes are extended in this work towards the modeling of IP/OOP interaction and combined failure mechanisms of URM assemblies. In the M‐DEM framework, shear and flexural damage are accounted for by zero‐thickness interface spring layers, whose layout is determined a priori as a function of the masonry texture, while crushing failure is modeled through homogenized finite element macro‐blocks. To adapt and validate this M‐DEM scheme to model IP/OOP interaction, past experiments on full‐scale C‐, U‐, and I‐shaped URM specimens tested under quasi‐static loading were simulated. The shake‐table response of a full‐scale C‐shaped URM assembly with openings was also numerically simulated up to collapse, representing a major improvement over previous macro‐element methods. After the comparison with experimental tests, a parametric investigation of the response of reference URM walls under combined IP/OOP actions was conducted, and the influence of previous IP damage on one‐ and two‐way OOP bending capacity is quantified. This aspect, despite being widely identified as of relevant interest, has only been marginally investigated in previous research, both experimentally and numerically. [ABSTRACT FROM AUTHOR]

Abstract Historical buildings still existing in different parts of the world were constructed with unreinforced masonry and have an acceptable capacity to transmit vertical loading, but they are very vulnerable against horizontal loading induced by earthquakes. In order to protect these buildings belonging to the patrimony of the humanity from this hazard, we need to understand the construction materials, structural elements and loading transmission mechanism. Moreover, to rehabilitate or retrofit them, it is necessary to develop an understanding process of the structure though monitoring and in-situ/laboratory experimental tests to stablish a diagnosis. The structural monitoring campaigns are helpful to investigate the mechanical and dynamic properties of the building. The use of installed thermal cameras and micro-sensors at strategic parts of the historical buildings represent a very interesting and non-destructive option to measure different parameters constantly and for long periods of time. The present paper aims at briefly describing the different involved processes in the monitoring and structural diagnosis of historical buildings which is fundamental in order to preserve them against the effects of earthquakes by means of rehabilitation works and strengthening. Moreover, it is presented a future perspective about non-destructive and non-invasive experimental tests and diagnosis with the use of new technologies. Resumen Los edificios históricos que aún existen en diferentes partes del mundo fueron construidos con mampostería no reforzada y tienen capacidad aceptable para transmitir cargas verticales, pero son muy vulnerables ante cargas laterales inducidas por sismos. Para proteger de esta amenaza a estas edificaciones que forman parte del patrimonio de la humanidad, debemos de entender los materiales constructivos, elementos estructurales y su mecanismo de transmisión de cargas. Para decidir entre rehabilitar o reforzar, se debe de realizar un proceso de entendimiento de la estructura a través de un monitoreo y pruebas experimentales en sitio y en laboratorio que permitan generar un diagnóstico. Los monitoreos estructurales sirven para investigar sus propiedades mecánicas y dinámicas. El uso de cámaras térmicas y micro-sensores en puntos estratégicos de los edificios históricos representan una opción muy interesante y no destructiva para medir diferentes parámetros de forma constante y por largos periodos de tiempo. El presente artículo tiene como objetivo describir de forma puntual los diferentes procesos involucrados en el monitoreo y diagnóstico estructural de edificios históricos que resulta fundamental para poder conservarlos ante los efectos de los sismos por medio de trabajos de rehabilitación y refuerzo. Además, se presenta una perspectiva futura sobre pruebas experimentales y diagnósticos no destructivos ni invasivos con el uso de nuevas tecnologías.

Researchers and practitioners widely employ simplified Equivalent Frame Models (EFM) for reproducing the in-plane governed response of unreinforced brick masonry (URM) structures, as they typically represent an acceptable compromise between numerical accuracy and computational cost. However, when considering URM structural systems with irregular opening distribution, the definition of the effective height and length of deformable components (i.e. pier and spandrel elements) still represents an open challenge. In this work, the influence of irregular distribution of openings on the predicted lateral response of full-scale URM façades was investigated. To this end, several geometrical combinations characterised by various degrees of irregularity were considered and idealised according to commonly employed EF discretisation approaches. Then, after a preliminary calibration process against experimental tests on both individual piers and a full-scale building façade, EFM results were compared with micro-modelling predictions, carried out within the framework of the Applied Element Method and used as a benchmark. Although in specific irregular configurations using some discretisation approaches, macro and micro-models converge to similar results, non-negligible differences in terms of initial lateral stiffness, base-shear and damage distribution were observed with other EF schemes or opening layouts, thus indicating that a careful selection of appropriate criteria is indeed needed when performing in-plane analyses of URM systems with irregular opening distributions. Finally, building on inferred simulated data, potential solutions are given to overcome typical EF discretisation issues and better approximate micro-modelling outcomes. [ABSTRACT FROM AUTHOR]

Estimation of the lateral load-carrying capacity of unreinforced masonry (URM) buildings is essential for their design, vulnerability assessment, and rehabilitation. Lateral strength of URM buildings can be assessed using experimental studies or numerical simulation, but conducting such studies on full-scale building specimens is expensive and requires huge computational effort and input data, which is not easily available. Therefore, the availability of test results and data is scarce in many developing countries having a huge concentration of URM buildings. Moreover, the quality and strength of masonry found in these countries are inferior to those found in some developed countries where data are available. This results in under-developed design codes and thus improper design and construction of URM buildings in seismically active regions of many developing countries. Therefore, simple analytical methods are required to be developed for the estimation of lateral load-carrying capacity of URM buildings with the help of systematic experimental and numerical studies on full-scale specimens. The paper presents a comparative assessment of the lateral strength of a URM building using experimental, analytical and numerical approaches. Pseudo-static in-plane cyclic tests were carried out over three full-scale URM walls with different opening configurations followed by testing of a single story URM building having a single room, constituting the walls, which were already tested. The walls and a building were then numerically analyzed in Abaqus and Strand7 to estimate the lateral load-carrying capacity. The lateral strength of individual walls was also estimated analytically using several existing methods. Finally, the effectiveness of combining the lateral strength of individual walls to estimate the lateral strength of full URM building was assessed that can be handy to the practicing engineers. [ABSTRACT FROM AUTHOR]

After the Zagreb earthquakes in March 2020, around 25,000 buildings were estimated damaged, most of them being in the historic city center. This fact is not that surprising since most of the city center buildings are unreinforced masonry structures that have not been assessed in quite some time and usually no retrofitting methods were ever applied. The rapid post-disaster assessment began the same day after the first earthquake occurred. Through mostly visual assessment methods, the basic idea is to identify the safety and usability of buildings in general. This type of assessment was also conducted in one of the oldest Croatian cultural institutions, Matica Hrvatska. It is a building of great historical significance and cultural value, as is most of the city center. Accordingly, this building was constructed with no consideration given to seismic events and with the use of traditional materials and building techniques. In the scope of this paper, urgent actions that were taken are shown with problems and challenges that occurred. Furthermore, the decision-making process after an earthquake is elaborated. In addition, a numerical model is developed in 3Muri software for structural modeling. A non-linear static pushover analysis is performed, and possible failure mechanisms are examined. Furthermore, real-life damage is compared to the software results, and a conclusion process of the building's usability is explained. In the end, the results obtained are analyzed and conclusions regarding the efficiency of the used software are drawn. [ABSTRACT FROM AUTHOR]

The suitability of 'design' height amplification factors (HAF) for the purpose of seismic assessment of existing non-structural unreinforced masonry (URM) components with known strength was evaluated through a numerical study. Four building typologies were included that represented pre-1940 URM construction in Australia and New Zealand. Through pushover and incremental dynamic analyses, the effects of diaphragm flexibility and nonlinear building response on floor accelerations were studied. It was found that Australia/New Zealand code procedures include significant inelastic building behaviour that reduces HAF. An interpretation was made on the applicability of the assumptions in the context of assessing non-structural URM components. [ABSTRACT FROM AUTHOR]

Increasing infrastructure projects in mega-cities are leading to greater vulnerability of heritage structures situated in the proximity. Heavy construction activities such as tunnelling, pile driving, deep excavation, movement of heavy vehicles, deep foundation, etc., are common in such projects. A combination of these activities leads to unintended distress in heritage structures, especially unreinforced masonry buildings. It is important to assess the structural health and vulnerability of such buildings. This would help in deciding on conservation strategies, including possible retrofitting of the structure. Bengaluru is one such mega-city which is bestowed with numerous heritage buildings, many of which are in proximity to the on-going metro project. All Saints' church is one such unique single-storied unreinforced masonry building neighbouring one of the underground metro stations proposed. The church was designed by Robert Fellowes Chisholm, a legend in architecture and pioneer of the Indo-Saracenic style, about 150 years ago. Its structural and architectural uniqueness is certainly worthy to be conserved. This paper brings out the details of the attempt made to assess the vulnerability of this structure due to possible lateral loads caused by ground motions induced by construction activities. An investigation has been made to collect the structural details required to model and analyse the structure. An attempt has been made to identify the regions in the load-bearing elements of the building which could experience higher levels of stresses due to lateral loads, using general purpose finite element software. During the study, it is observed that there are certain unique structural elements that have been robustly configured into the architectural features and thus rendered the building healthy despite its age. It is concluded that these unique structural elements need to be carefully monitored and protected to conserve the heritage building. [ABSTRACT FROM AUTHOR]

Masonry buildings are generally vulnerable to seismic action, as evidenced extensively in past earthquakes. In order to improve their seismic performance, several modifications have been introduced, such as reinforcing or confining the masonry. This paper presents a seismic analysis and fragility assessment procedure for non-engineered masonry building typologies, employing the applied element method (AEM). Compared to buildings with stiff diaphragms, the conventional pushover-based procedure is challenging for the seismic assessment of masonry buildings with flexible diaphragms, due to the lack of a global box-like behaviour. This study first presents a novel and validated method for nonlinear pushover analysis, independent of the type of diaphragm action on the building, by applying incremental ground acceleration and by considering suitable engineering demand parameters for the assessment of lateral capacity. Based on the failure mechanisms, a seismic performance assessment and fragility evaluation approach is then proposed, for reliable accounting of both the in-plane and out-of-plane failure modes. Finally, the proposed methodology is applied to a number of unreinforced and confined masonry school buildings with different seismic detailing levels, as often found in the Himalayan belt and beyond.

Unreinforced masonry (URM) walls, found in most historical buildings in Indonesia, are relatively brittle with wide variety of material properties. The behaviour of URM walls is very complex, especially when subjected to seismic excitation. In this research, a finite element modelling was set up in order to analyse the seismic performance of URM wall experimental test units, with and without strengthening material. The analysis was conducted using SAP2000 computer program. Three dimensional solids and springs as link connectors were assigned to represent the masonry behaviour. This research aims to compare results obtained from the computer analysis and the previously conducted laboratory experiments. The effectiveness of Kevlar fibre material, which was installed on both wall surfaces and modelled as truss element was also investigated. It was found that the failure mechanisms shown by the SAP2000 model was similar to the laboratory test results. The use of Kevlar Fibre as strengthening material was found able to significantly increase the stiffness and shear capacity of the URM wall.

The authors developed two types of block systems, consisting only of main and key blocks, without joint mortar, to improve the in- and out-of-plane seismic performances and enhance the workability. Two types of block systems have different key block shapes. One is the peanuts shape, and the other is the H shape. The proposed block systems have a half-height difference between the main and key blocks, to significantly improve seismic performance in in- and out-of-plane directions, compared to typical masonry wall with joint mortar. In this study, in order to evaluate the out-of-plane seismic performance of the proposed block systems, two types of block walls are experimentally investigated, including the typical block wall. Firstly, the shaking table tests are carried out to investigate the fundamental out-of-plane behaviors of three specimens. Next, four-point bending tests are planned to evaluate the out-of-plane seismic performance, since all specimens do not occur the out-of-plane collapse in the shaking table tests from the preliminary calculation. In this paper, the development of predominant period, profiles of acceleration and displacement, and maximum tensile strength of each specimen are discussed in detail. As a result, the maximum loads of the proposed block walls were about three to four times that of the typical block wall. This result means that the proposed block system has significantly improved seismic performance in the out-of-plane direction. [ABSTRACT FROM AUTHOR]

The shear properties of unreinforced masonry are key parameters used in order to understand the behaviour of these structures under horizontal actions. These characteristics are usually determined using Destructive Testing (DT) methods. However, this typology of tests is not always suitable due to both their high impact and cost. The present work aims to design, analyze and apply an innovative Minor Destructive Testing (MDT) technique for the determination of the shear mechanical properties. To limit the impact on the structure, the Flat Jack (FJ) technique was adopted. The geometrical configuration, chosen among six different layouts, was studied in order to comprehend the roleplayed by different parameters and to have then a mathematical model representative of the stresses inside of the sample. Finally, four in situ tests were executed and are analyzed and discussed. [ABSTRACT FROM AUTHOR]

The overall seismic resistance of unreinforced masonry (URM) systems that exhibit box-behavior mainly relies on the lateral force capacity of structural components. Despite the fact that it is widely accepted that masonry bond pattern might considerably affect the in-plane performance of URM members, this aspect has not fully addressed experimentally or numerically. In this paper, calibrated numerical models, developed within the framework of the Distinct Element Method, are used to simulate the quasi-static lateral response of URM piers under several combinations of boundary conditions, vertical pressures and aspect ratios, as well as a large number of typically-employed periodic and quasi-periodic bond patterns. The employment of time, size and mass scaling, and dynamic relaxation procedures, combined with the introduction of equivalent interface properties to represent the effect of cyclic damage through monotonic loading schemes, provided a significant reduction of computational cost, thus enabling a comprehensive parametric study to be carried out within an acceptable timeframe. The results show that the bond pattern has an appreciable influence on the response of laterally-loaded URM panels, motivating the possibility of including this aspect in the assessment of existing URM structures. Analytical formulations were also inferred by fitting numerical data, thus enabling the findings of this work to be readily implemented in assessment using simplified models. [ABSTRACT FROM AUTHOR]

A test programme consisting of four half-scale URM walls was conducted under quasi-static cyclic loading to evaluate the negative influence of openings. Test results showed that the masonry adjacent to the opening experienced significant damage, and the specimens with a door opening was found to have complete detachment of the masonry pier, resulting in a reduction in the capacity of more than 25%. Furthermore, a detailed parametric nonlinear finite element analysis was performed to assess the influence of parameters affecting the in-plane load capacity of the URM wall. Numerical results showed that depending upon the size and location of openings and the material and geometric properties of walls, the in-plane load capacity was reduced by 6–82%. Considering the results of available experimental studies and present numerical analyses, a simplified equation was proposed to estimate the reduction in the in-plane load capacity of the specimen with different types of openings. The analytical study demonstrated that the proposed equation effectively provided reliable and consistent predictions of the strength reduction factor for walls with different types of openings. • Assess opening's effect on lateral load capacity of masonry wall via cyclic test. • Effect of various parameters on in-plane strength reduction using FE simulations. • Size and position of opening in walls significantly affect in-plane load capacity. • Develop a simplified relation to estimate strength reduction for opening in walls. [ABSTRACT FROM AUTHOR]

A prolonged seismic sequence struck the regions of Central Italy between August 2016 and January 2017, causing several fatalities and widespread damage to the built environment. The main objective of this work was to study the structural and seismic behavior of “Pietro Capuzi” school, located in Visso, in the Marche region, which was severely damaged by the 2016-2017 Central Italy Earthquake. A 3D finite element (FE) model of the entire school was prepared, adopting a macro-modeling approach to represent masonry materials. An eigenvalue analysis was initially performed in order to identify the dominant modes of vibration of the structure and to calibrate the numerical model according to the results of the dynamic identification tests. Afterwards, nonlinear static analyses were performed on the calibrated FE model to evaluate the seismic response of the structure. Finally, the numerical results obtained in terms of crack pattern and failure mechanisms were compared with the damage experienced by the building. The numerical model proved to accurately predict the seismic response exhibited by the structure during the past seismic events.

Urban renewal projects typically involve redevelopments of under-utilized old buildings and revitalizing precious land resources. Due to architectural and social-economic reasons, historical façades are sometimes retained, and new constructions are built behind them. This allows the historical façade, typically the street elevation, to remain while new real estate can be redeveloped. In the profession of architecture, this is called façadism. In many cases, these historical façades are constructed with unreinforced masonry (URM). When these facades are retained and the remaining of the building is demolished, they become free-standing walls. Temporary supports are required throughout construction works and the retained façades must be designed to prevent excessive movements, allowed for differential movements and to resist wind forces. These historical façades were made of brittle materials and were constructed many decades ago before modern design standards and materials are available. They possess very little ductility and become vulnerable when subjected to ground shaking. The present study suggests a structural system that attempts to mitigate seismic risk of façadism constructions effectively. The structural system divides the new construction, which can be a reinforced concrete structure or a steel frame structure, into two separate frames. A seismic gap is introduced between them and produces two systems of different vibrational characteristics. Supplemental energy dissipating devices such as viscous fluid or friction dampers are placed in-between adjacent floors. The proposed structural system utilizes the different vibrational responses of two frames to facilitate energy dissipation in dampers. In this article, governing equations are presented, followed by numerical simulations using historical earthquake acceleration histories. Results demonstrate that the suggested structural system is an effective methodology to suppress seismic responses of the façade and the new construction. It is concluded that damage on the retained façades can be prevented, and at the same time seismic responses to the newly constructed structure can be controlled.

Urban renewal projects involve redevelopments of under-utilised old buildings and revitalisation of precious land resources. Due to architectural and social-economic reasons, historical façades are sometimes retained, and new constructions are built behind them. This allows the historical façade, typically the street elevation, to remain while new real estate can be developed. In the profession of architecture, this is called façadism. In many cases, these historical façades are constructed with unreinforced masonry (URM). During demolition and construction, a temporary shoring retention frame is required prior to permanent connection to the new construction. These historical façades were made of brittle materials and were constructed many decades ago before modern design standards and materials were available. They possess little ductility and become vulnerable when subjected to ground shaking. Typically, the retained façades are treated as non-structural components and little attention is paid to their seismic performance. While most prior studies focus on strengthening of masonry or improving connection robustness between façades and the main structure, the present study attempts to take a different approach by limiting displacement demand on the façade. A new structural form is suggested which divides the new construction into two separate frames. A seismic gap is introduced between them and produces two structures of different vibrational characteristics. Supplemental energy dissipating devices such as viscous fluid or friction dampers are placed in-between adjacent floors. The façade is attached to a frame with smaller seismic mass and higher stiffness, while the second frame will undergo larger displacements in an event of ground shaking. In this manner, full advantage of supplementary energy dissipation is utilised, while protecting the façade from excessive displacements. In this article, governing equations are presented, followed by numerical simulations using historical earthquake acceleration histories. Results demonstrate that the suggested structural form is an effective methodology to suppress seismic responses of the façade and the new construction. It is concluded that damage on the retained façades can be prevented, and at the same time seismic responses to the newly constructed structure can be controlled. [ABSTRACT FROM AUTHOR]

Unreinforced masonry walls (URM) in old buildings are vulnerable to collapse upon receiving high lateral inertia force due to earthquakes. However, a high strength fiber material such as Kevlar fiber has been identified as able to improve the URM-Wall performance, especially in shear strength enhancement. In this research, the seismic performance of an URM-Wall was analysed using SAP2000 by modeling the wall with three dimensional solid elements. Solids and springs as link connectors were assigned to represent the masonry behavior. The aim of this research is to compare between results obtained from the computer analyses and the previously conducted laboratory experiments. The effectiveness of Kevlar material installed in the diagonal directions of both wall surfaces was investigated. It was found that the failure mechanism shown by the SAP2000 model is similar to the laboratory test results.

Despite numerous studies on seismic performance of masonry infilled reinforced concrete frames have been conducted, experimental study on effect of type of lateral load on masonry infilled reinforced concrete frames is sparse. This paper investigates the seismic performance of masonry infilled reinforced concrete frames with different aspect ratios subjected to monotonic and cyclic loadings. Six half-scale, single-storey, single-bay frame specimens designed according to code provisions commonly adopted in Malaysia were tested. Behaviours of frames were assessed based on observed failure modes, strength, stiffness, ductility and energy dissipation capacity. Experimental result reveals that typical infilled frame in Malaysia has high tendency to fail under shear on columns. Type of loading does not affect strength of both bare frames and infilled frames. However, the drift to reach peak strength drops about 40–52% for infilled frames subjected to cyclic loading as compared to monotonic loading. Initial stiffness of infilled frames is found elevated with slower stiffness degradation under the influence of cyclic loading. Ductility of infilled frames subjected to cyclic loading is 48% higher than those subjected to monotonic loading, regardless of aspect ratio. A total of 84% increase in energy dissipation is observed with 60% of increment in bay length. [ABSTRACT FROM AUTHOR]

This data article provides experimental data obtained from the incremental dynamic shake-table testing of four single leaf unreinforced masonry (URM) walls constructed in Calcium Silicate (CS) bricks reported in “Two-way bending experimental response of URM walls subjected to combined horizontal and vertical seismic excitation” [1]. These walls were tested in the second phase of a larger experimental campaign addressing the out-of-plane (OOP) response of full-scale URM panels in two-way bending configurations at EUCENTRE, Pavia, Italy. Data corresponding to the first phase of testing for four single leaf and one cavity wall has already been made available through Tomassetti et al. [2] and the information necessary to interpret these results can be found in Graziotti et al. [3]. The walls of the tests reported in this data article were constructed in an intentionally weakened mortar but using the same Calcium Silicate (CS) bricks as Graziotti et al. [3]. The walls were also tested in boundary conditions that were not addressed in [3] and a specimen was also subjected to simultaneous horizontal OOP and vertical seismic excitation in one of the tests. Videos documenting the failure of specimens tested in both phases of the experimental campaign can be viewed online on YouTube [4].

In many countries, buildings are usually made of unreinforced clay masonry walls, especially in Colombia. These constructions have low resistance and ductility, and are very vulnerable to seismic events, due to their low capacity of energy dissipation. This paper reports the results obtained from a research project that evaluates the behavior of reinforced masonry walls under lateral loads. The reinforcement was made using Carbon Fiber Reinforced Polymers (CFRP). In the test program, eight (8) clay masonry walls were built using hollow brick. Four (4) of them were 1,23 m long and 1,90 m high and the remaining four (4) were 2,47 m long and 1,90 m high. Four (4) walls were tested with a static lateral load and four (4) with a cyclic lateral load in its plane. Results revealed that the presence of the reinforcement material significantly increased the ultimate load and deformation capacity, provided that the material has a suitable anchoring system.

Unreinforced masonry (URM) buildings with cavity walls, typically constituted by the assembly of a loadbearing inner leaf weakly coupled to an outer veneer with no structural functions, are widely present in a number of regions exposed to tectonic or induced seismicity, including the Groningen province (The Netherlands), which has lately experienced low-intensity ground shaking due to natural gas extraction. Recently, experimental evidence has shown that the lack of seismic details, and, above all, the presence of large ground floor openings, makes these structures particularly vulnerable towards horizontal actions. In this endeavour, advanced discrete element models, developed within the framework of the Applied Element Method (AEM), are employed to investigate numerically the impact of ground floor openings percentage on the dynamic behaviour of cavity wall systems representative of the typical Dutch terraced houses construction, namely low-rise residential URM buildings with rigid floor diaphragms and timber roof. Firstly, the model is validated through comparison with a shake-table test of a full-scale building specimen, tested up to near-collapse. Then, a comprehensive numerical study, which featured several combinations of ground-floor openings and the application of various acceleration time-histories up to complete collapse, is undertaken. The ensuing results allowed a comparison of the fragility associated with each of the considered openings layouts, showing how the presence of large ground floor openings may significantly increase the seismic vulnerability of typical URM Dutch terraced houses. [ABSTRACT FROM AUTHOR]

Different codes provide a range of values for structural behaviour factor for various masonry building systems. High variation in structural behaviour factors in different codes arises mainly due to the lack of information from experimental studies. Thus, the present paper highlights investigation of behaviour of different masonry construction systems through full-scale tests on masonry buildings subjected to cyclic displacement. Six tests, out of which three on virgin masonry building systems, employing unreinforced masonry (URM), reinforced masonry (RM) and confined masonry (CM) having similar geometrical, material, constructional features and test procedures were conducted. The remaining three building models tested included repaired unreinforced masonry (URM-REP), retrofitted unreinforced masonry (URM-RET) and retrofitted reinforced masonry (RM-RET). Observations and data from the experiments have been co-related between damage index, grade of damage and displacement capacity, thereby estimation of structural behaviour factor for different masonry building typologies. The analysis shows that the ranges of structural behaviour factor mentioned in codes are adequate for URM and RM, while the same for CM is conservative, which can be relaxed. Also, it has been noticed that there is a substantial increase in structural behaviour factor for repaired and retrofitted masonry structures, thus proving the structural adequacy of retrofitting measures. [ABSTRACT FROM AUTHOR]

The authors developed two types of block systems consisting only of main block and key block without joint mortar to improve the seismic performances and to enhance the workability. Two types of block systems have different key block shapes: one is the peanut shape, and the other is the dumbbell shape. The proposed block systems have a half-height difference between the main block and the key block to significantly improve seismic performance compared to typical masonry walls with joint mortar. In this study, in order to evaluate the in-plane seismic performance of the proposed block systems, two types of block walls are experimentally investigated, including the typical block wall. In the tests, three full-scale, single-story specimens are tested under in-plane cyclic loading, and failure patterns and cracks are carefully observed. In this paper, the in-plane loading bearing capacity, energy dissipate capacity and reuse ratios of block walls are discussed in detail. As a result, the deformability, energy absorption capacity and reuse ratio of the proposed block systems were considerably higher than those of a typical block system. [ABSTRACT FROM AUTHOR]

Structural design of unreinforced masonry buildings in The Netherlands, recently exposed to low-intensity ground motions induced by gas extraction, was not originally conceived for earthquake-resistance. Indeed, the presence of both large openings and flexible diaphragms, and the lack of any specific seismic consideration or detailing significantly increase their vulnerability towards horizontal loading. In this paper, the Applied Element Method (AEM), which explicitly represents the discrete nature of masonry, is used to simulate the shake-table response of a full-scale building specimen representative of a typical Dutch detached house made of unreinforced solid clay-brick masonry. Using this modelling strategy, the damage evolution, as well as both global failure mode and hysteretic behaviour, are described. The results show a good agreement with the experimentally observed response, confirming the capabilities of the AEM in reproducing effectively the behaviour of masonry structures, whilst simultaneously keeping computational costs within acceptable limits for this type of detailed modelling. [ABSTRACT FROM AUTHOR]

Cyclic shear tests on walls made of clay block masonry Cyclic shear tests are a common method to assess the load‐bearing capacity and the deformation behaviour of walls under dynamic loads in the horizontal direction, such as those that occur during earthquakes. In the presented work, cyclic shear tests on 36 walls made of different types of masonry are described, the test results are shown and compared with calculated resistances according to Eurocode 6. After a list of the building materials used, the materials used and their dimensions are given for all examined walls. This is followed by a description of the experimental setups used at the institutes UTCB in Bucharest and ZAG in Ljubljana. The main part is the presentation of the measured values regarding achievable loads and drift values, as well as the determination of a bilinear approximation for each test. The envelope curves of the hysteresis loops of all experiments are then shown and compared. Finally, a comparison of the test results to calculated resistances according to Eurocode 6 is shown. With these investigations it could be shown that walls made of masonry have large drift capacities and that the assessment with the models of the Eurocode 6 delivers very realistic results. Furthermore, it could be shown, that conservative results are achieved when the resistance of masonry from concrete‐filled blocks is calculated with a composite stone strength, especially for walls with a higher degree of reinforcement. [ABSTRACT FROM AUTHOR]

The impact of adopting different dynamic soil–structure interaction (SSI) models on the assessment of seismic fragility functions for buildings with pile foundations is studied herein. Given the importance on seismic response of the coupling of structure, foundation and soil, and the challenges posed on modelling dynamic SSI, especially when soil nonlinearity plays a significant role, the linear substructure approach is initially adopted by implementing two different models, followed by the use of a nonlinear pile-head macro-element. The first model is one-dimensional and includes, between the foundation node and the ground, only a translational elastic spring and a dashpot, whose stiffness and viscous damping are retrieved from the real and imaginary parts of the dynamic impedance at the first natural frequency of the structure. The second and more refined model is a Lumped-Parameter Model accounting for frequency dependence of the coupled horizontal and rotational impedances in a two-dimensional response. A nonlinear pile-head macro-element model is introduced afterwards to explore the sensitivity of fragility functions to the linearity assumption. This approach models the soil nonlinear behaviour at near-field, as well as the far-field dynamic impedance and energy dissipation through radiation damping, by condensing the entire soil-foundation system into a single nonlinear element at the base of the superstructure. In all models, the superstructure is represented in a simplified way as a nonlinear single-degree-of-freedom system. The comparison between the adopted approaches is evaluated in terms of their effects on the characterisation of fragility functions for unreinforced masonry buildings with pile foundations. [ABSTRACT FROM AUTHOR]

A formulation is presented for simplified evaluation of the roof acceleration response for the purpose of assessing non-structural components in unreinforced masonry buildings with flexible diaphragms excluding torsional effects. The method is based on modal calculations that are further studied through nonlinear time-history analysis (NLTHA) of four case study buildings. The NLTHA results for a relatively small level of ground shaking was used to validate the overall ability of the simplified modal method to predict the diaphragm flexibility effects. The NLTHA results were also used to discuss the effects of the building inelastic response in the conservatism of the simplified modal technique. It was found that, in lieu of a comprehensive modal analysis, it is possible to calculate roof accelerations in symmetric low-rise buildings with flexible diaphragms using a simplified two-mode modal method. Based on this study, a predictive method is proposed for conservative estimation of peak roof accelerations in these buildings. [ABSTRACT FROM AUTHOR]

The Himalayan region is one of the major seismic areas in the world. However, similar to many other seismically active locations, there are substantial numbers of unreinforced masonry (URM) buildings; the majority of which have not been designed for seismic loads. Past seismic events have shown that such buildings are highly vulnerable to earthquakes. Retrofitting of these URM buildings is an important concern in earthquake mitigation programs. Most government school buildings in rural areas of northern India are constructed of unreinforced masonry. These school buildings are socially important structures and serve as a crucial resource for rehabilitation during any disaster. The effectiveness of ferrocement (FC) to create a URM-FC composite is described in this study by estimating the performance and fragility of a URM school building before and after a retrofit. Analytical models, based on the equivalent frame method, are developed and used for nonlinear static analysis to estimate the enhancement in capacity. The capacity enhancement due to retrofitting is presented in terms of the maximum PGA sustained and damage probabilities at the expected level of earthquake hazard. [ABSTRACT FROM AUTHOR]

After the Zagreb earthquakes in March 2020, around 25,000 buildings were estimated damaged, most of them being in the historic city center. This fact is not that surprising since most of the city center buildings are unreinforced masonry structures that have not been assessed in quite some time and usually no retrofitting methods were ever applied. The rapid post-disaster assessment began the same day after the first earthquake occurred. Through mostly visual assessment methods, the basic idea is to identify the safety and usability of buildings in general. This type of assessment was also conducted in one of the oldest Croatian cultural institutions, Matica Hrvatska. It is a building of great historical significance and cultural value, as is most of the city center. Accordingly, this building was constructed with no consideration given to seismic events and with the use of traditional materials and building techniques. In the scope of this paper, urgent actions that were taken are shown with problems and challenges that occurred. Furthermore, the decision-making process after an earthquake is elaborated. In addition, a numerical model is developed in 3Muri software for structural modeling. A non-linear static pushover analysis is performed, and possible failure mechanisms are examined. Furthermore, real-life damage is compared to the software results, and a conclusion process of the building’s usability is explained. In the end, the results obtained are analyzed and conclusions regarding the efficiency of the used software are drawn.

The authors developed two types of block systems, consisting only of main and key blocks, without joint mortar, to improve the in- and out-of-plane seismic performances and enhance the workability. Two types of block systems have different key block shapes. One is the peanuts shape, and the other is the H shape. The proposed block systems have a half-height difference between the main and key blocks, to significantly improve seismic performance in in- and out-of-plane directions, compared to typical masonry wall with joint mortar. In this study, in order to evaluate the out-of-plane seismic performance of the proposed block systems, two types of block walls are experimentally investigated, including the typical block wall. Firstly, the shaking table tests are carried out to investigate the fundamental out-of-plane behaviors of three specimens. Next, four-point bending tests are planned to evaluate the out-of-plane seismic performance, since all specimens do not occur the out-of-plane collapse in the shaking table tests from the preliminary calculation. In this paper, the development of predominant period, profiles of acceleration and displacement, and maximum tensile strength of each specimen are discussed in detail. As a result, the maximum loads of the proposed block walls were about three to four times that of the typical block wall. This result means that the proposed block system has significantly improved seismic performance in the out-of-plane direction.

Unreinforced masonry (URM) structures are vulnerable to earthquakes; thus, materials and techniques for their strengthening and restoration should be developed. However, the materials used in some of the existing retrofitting technologies for URM and the waste produced at its end-of-life are unsustainable. The production of ordinary Portland cement (OPC) worldwide has enormously contributed to the global carbon footprint, resulting in persistent environmental problems. Replacing OPC with geopolymers, which are more sustainable and environmentally friendly, presents a potential solution to these problems. Geopolymers can replace the OPC component in engineering cementitious composites (ECC), recommended to strengthen and restore URM structures. In the present paper, the state-of-the-art knowledge development on applying geopolymers in URM structures is discussed. The discussion is focused on geopolymers and their components, material characterization, geopolymers as a strengthening and restoration material, and fiber-reinforced geopolymers and their application to URM structures. Based on this review, it was found that the mechanical properties of geopolymers are on par with that of OPC; however, there are few studies on the mentioned applications of geopolymers. The characterization of geopolymers’ mechanical and physical properties as a restoration material for URM structures is still limited. Therefore, other properties such as chemical interaction with the substrate, workability, thixotropic behavior, and aesthetic features of geopolymers need to be investigated for its wide application. The application method of geopolymer-based ECC as a strengthening material for a URM structure is by grouting injection. It is also worth recommending that other application techniques such as deep repointing, jacketing, and cement-plastering be explored.