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• A timber system is proposed for the seismic retrofit of URM buildings. • Analytical equations are derived for design against different failure modes. • Wall in-plane and out-of-plane responses, diaphragms and connections are addressed. • The proposed equations are applied to case-study buildings and structural members. • Good agreement between analytical calculations and experimental data is shown. An innovative timber retrofit was investigated at the EUCENTRE and at the University of Pavia, Italy, as part of a comprehensive research campaign on the seismic vulnerability of existing unreinforced masonry buildings subjected to induced seismicity in The Netherlands. The retrofit system consists of timber frames, connected to the masonry piers and to the floor diaphragms, and oriented-strand board sheathing nailed to the frames and to flexible timber diaphragms. Starting from the main critical aspects observed in experimental tests, the proposed solution was conceived to enhance the in-plane and out-of-plane capacities of masonry piers, improve the overall wall-to-diaphragm connections, increase the floor diaphragm stiffness and strength, and allow possible integration with energy efficiency upgrades. This paper, the first of a series of two, focuses on the conceptual bases of the seismic retrofit system and on the analytical equations that can be used for the design of its components. Moreover, a step-by-step design procedure is presented to guide the reader through the application of these equations. A companion paper [1] will discuss the validation of the analytical formulation with the experimental data from quasi-static cyclic and dynamic shake-table tests on building components and complete specimens. [ABSTRACT FROM AUTHOR]

• A timber system is proposed for the seismic retrofit of URM buildings. • Analytical equations are derived for design against different failure modes. • Wall in-plane and out-of-plane responses, diaphragms and connections are addressed. • The proposed equations are applied to case-study buildings and structural members. • Good agreement between analytical calculations and experimental data is shown. This paper is the second of a series of two, discussing the analytical assessment of the seismic behavior of an innovative timber retrofit for unreinforced masonry structures. The retrofit system consists of timber frames, connected to the masonry piers and to the floor diaphragms, with oriented-strand board sheathing nailed to the frames and to flexible timber diaphragms. The companion paper [1] focused on the conceptual bases of the proposed solution, providing analytical equations for the design of its components, and a step-by-step design procedure for their practical application. In this paper, the proposed formulations are validated against the experimental data coming from in-plane quasi-static shear-compression tests on masonry piers and dynamic shake-table tests on a full-scale building prototype. These tests were performed on nominally-identical specimens in both bare and strengthened configurations, allowing a direct comparison between the experimental and calculated retrofit contribution. In particular, the analytical formulation was applied to reproduce the in-plane response of individual piers, to reproduce the base shear-interstory drift envelope of the building specimens, to assess the out-of-plane strength of walls, and to validate the flexible diaphragm enhancement. Overall, the proposed formulations revealed a good match with the observed retrofit performance and failure mechanisms. [ABSTRACT FROM AUTHOR]

• Combination of unreinforced masonry structural logic and 3D-concrete printing. • Form-finding loop with Thrust Network Analysis and Discrete Element Modelling method. • Application of Discrete Element Modelling and Finite Element Modelling to assess global and local structural behaviour. • 3D-concrete-printed components as primary structural elements with layers oriented perpendicular to the compressive flow of forces. • Dry-assembled unreinforced concrete masonry structure with a clear separation of the different materials enhancing the circularity of the structural system. • Computational pipeline for the design of 3DCP unreinforced masonry structures. This paper describes the structural design and engineering of " Striatus" , a 3D-concrete-printed unreinforced masonry pedestrian bridge built in Venice in 2021 as part of the Time Space Existence exhibition organised by the European Cultural Centre. The project combines the latest developments in 3D concrete printing with the structural principles of historic unreinforced masonry. Typically, the structural applications of 3D concrete printing are limited to elements such as columns and walls loaded vertically, perpendicularly to the horizontal printing layers, to formwork elements or secondary structural elements. Indeed, fabrication constraints, delamination issues and the low tensile strength of the concrete have been seen as limiting factors to 3D concrete printing for structural applications demanding resistance to bending or predominant loading directions not perpendicular to the printing layers. By using unreinforced-masonry structural principles, this paper shows that structural elements spanning space horizontally, such as a pedestrian bridge, can be built by using the 3D concrete printing components as the main structure, working only in compression, loaded perpendicularly to the printed layers. Furthermore, as a compression-only structure following masonry principles, Striatus enabled the use of unreinforced concrete without any mechanical or chemical connections between the elements and the separation of concrete and steel, only used for the supports and to equilibrate the horizontal thrust of the arch effect through the tension ties. This work shows how the application of unreinforced masonry principles to 3D concrete printing offers new opportunities in terms of structural design and represents a strategy to increase sustainability by reducing material consumption and allowing reusability and recyclability of the structure. Finally, this paper discusses the critical aspects related to the design of Striatus from an engineering and construction point of view. [ABSTRACT FROM AUTHOR]

This paper introduces novel analysis procedures for the structural assessment of masonry earth retaining structures subjected to traffic loading. Given their substantial presence, particularly in transportation networks of historical cities, and the challenges posed by ageing, deterioration, and exposure to loads beyond their original design considerations, this research highlights the necessity of accounting for potential load redistribution mechanisms during their assessment. This can prevent overly conservative interventions that may not be necessary and also contravene sustainability and heritage preservation principles. Four distinct analysis procedures – 2D monotonic, 3D monotonic, 3D static moving load and 3D dynamic moving load – are developed, each progressively more refined than its predecessor in capturing potential load redistribution mechanisms in masonry earth retaining structures. These mechanisms may develop due to the dynamic loading conditions of the vehicular passage, the 3D structural configuration of retaining structures, and non-linear material behaviour. By comparing the structural capacity evaluated using the four procedures, contributions from different sources of load redistribution can be separately quantified, aiding in the reduction of conservatism inherent in less refined assessment procedures. The application of the developed procedures and consequent quantification of load redistribution is demonstrated through a case study of an existing masonry retaining structure in Amsterdam, the Netherlands. • Analysis procedures for masonry earth retaining structures under traffic loading. • 2D monotonic, 3D monotonic, 3D static and 3D dynamic moving load procedures. • Load redistribution is due to dynamic loading and 3D structural configuration. • Demonstrated application to a case study in Amsterdam, the Netherlands. [ABSTRACT FROM AUTHOR]

Highlights • 32 masonry wallets were tested under out-of-plane loading. • Both fly-ash and clay bricks of two different sizes were used. • Polypropylene (PP) band and steel wire mesh (WM) were used to strengthen the wallets. • Flexural strength, load-displacement behaviour, stiffness and energy dissipation capacity were discussed. • Both the strengthening techniques are effective in delaying the collapse of the structure. Abstract The collapse of the masonry wall occurs mainly due to inadequacy of load transferring mechanism of out-of-plane behaving wall during earthquake, and is the cause for huge loss of property and life of inhabitants. Hence, an experimental program was carried out to investigate the efficiency of masonry wall in flexural loading. Total 32 specimens were tested. Some specimens were unreinforced and others were reinforced. In India, both clay brick and fly-ash brick are commonly used to construct the masonry wallets. Hence, these walls, were tested under four-point loading method as per ASTM E518 -10 recommendations to investigate the influence of different brick composition in out-of-plane behaviour of wall. In addition, comparative study was also made between traditional full-size and half-scale bricks to check its suitability for the construction of scale-down models. Cost effective materials such as polypropylene (PP) band and steel wire mesh (WM) were used to strengthen these walls. The result shows that both the strengthening techniques are effective in delaying the collapse of the structure, also enhancing the flexural strength and ductility, and this paper presents these outcomes. This paper also presents the cracking load, load-displacement behaviour, stiffness and energy dissipation capacity. Finally, an analytical formulation has also been developed to validate the cracking load of the wall with experimental results. [ABSTRACT FROM AUTHOR]

• Continuum damage and brick-to-brick modeling techniques are compared. • A masonry wall strengthened with bed joint reinforced repointing is considered. • For un-strengthened case, all models provide accurate predictions of crack pattern. • For strengthened case, the simplified brick-to-brick model provides the best results. • Modelling of pre-damage should be considered with care. Bed joint reinforced repointing is a retrofitting technique for unreinforced masonry structures that is commonly applied in the Netherlands to repair settlement-induced damage. Using this technique, the bed joints of masonry walls are reinforced with steel rebars that are embedded in a high strength repair mortar. Due to the increase of induced seismic events in the northern part of the Netherlands, an experimental study was carried out at Delft University of Technology to investigate the performance of this retrofitting technique for combined settlement and seismic loading. This paper aims to simulate the experimental results, with a focus on the comparison of different finite element modelling approaches for studying both un-strengthened and strengthened full-scale tested walls. To that end, three different models are investigated – comprising both macro (continuum) and simplified and detailed micro (brick-to-brick) modelling approaches. The bricks and mortar joints are modelled as one homogenous continuum in the macro model, whereas in the two brick-to-brick models these structural components are modelled separately, with the detailed model including interface elements to simulate the brick–mortar bonds. Nonlinear pushover analyses are subsequently carried out using all three modelling approaches, for both monotonic and cyclic loading cases. Based on these analyses, the detailed brick-to-brick model was found unsuitable to simulate the strengthened wall because cracks in the model mainly occur in the form of opening of the brick–mortar bond interfaces, while smeared cracking in the plane stress elements of the mortar joints is very limited. Similarly, the continuum damage model was found to be inaccurate when pre-existing damage in the experiment needed to be taken into account. The continuum damage model also showed lower axial stresses in the rebars, compared with the simplified brick-to-brick model, as the former does not allow for the direct assignment of material properties for the high strength repair mortar in the strengthened joints. [ABSTRACT FROM AUTHOR]

The recent high-intensity 2015 Gorkha (Nepal) earthquake, has caused not only a substantial death toll and huge economic losses, but also heavy damage to many public residential buildings. Both URM and RC buildings suffered low to heavy destruction. Each earthquake places buildings, in the affected area, to an earthquake withstand test and provides an opportunity to learn lessons for future preparedness to encounter the challenge of disaster. The Gorkha earthquake sequences delivered unprecedented opportunity to augment the understanding on seismic performance of public residential buildings. Along with presenting the seismicity and losses suffered during the earthquake, the current paper highlights earthquake induced damages to residential buildings in Kathmandu valley, both URM and RC buildings. This paper is also motivated to point out the faintness in past to current constructional practice of residential buildings and convey awareness to stake holders for future safer building construction practice. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents an effective and accurate computational strategy for unreinforced brick masonry structures. Mesoscale descriptions allow a realistic representation of the nonlinear structural behaviour of URM, but can pose prohibitive computational demands for large-scale problems. To overcome this drawback, the computational strategy presented in the paper employs the domain partitioning approach, which is coupled with an accurate mesoscale finite element model. This allows the effective parallelisation of the nonlinear structural analysis simulation, where significant speed-up can be achieved in the nonlinear analysis of large masonry structures. The potential and effectiveness of the proposed computational strategy are shown through numerical examples, where full-scale masonry structures are considered. [Copyright &y& Elsevier]

• This paper presents the test results of URM walls strengthened with ECC. • URM walls failed with the flexural-dominant mode. • ECC layers can significantly improve the ductility of specimens. • A calculated mode was proposed for the URM walls strengthened with ECC overlay. Engineered cementitious composite (ECC) is a typical fiber reinforced cementitious composite with a strain-hardening behavior in tension and can be easily applied to strength masonry structures. This work studies the static behavior of flexural-failure dominant unreinforced masonry (URM) walls strengthened with ECC overlay. Five URM walls were constructed and four of them were reinforced: a wall strengthened with steel mesh, a wall strengthened with single-side ECC overlay, two walls strengthened with double-sides ECC overlay. One of the two double-sides ECC-strengthened walls was designed with a tie column. The effectiveness of reinforcement plans and tie column on the failure mode, lateral strength, hysteresis response, stiffness degradation, energy dissipation capacity, residual displacement and equivalent viscous damping is analyzed. The experimental results indicate that the ECC retrofit techniques can significantly improve the ductility of URM walls. The walls strengthened with ECC overlay exhibit significant increase in the wall drift and energy dissipation and decrease in the residual displacement. Finally, a calculated model for the ECC reinforced walls was proposed to estimate the maximum lateral strength. [ABSTRACT FROM AUTHOR]

Highlights • Rheological linear elastic-perfectly viscoplastic model for masonry multi-layer bed joints is presented. • Model consists of an elastic spring connected in series with the frictional slider and a viscous damper. • Monotonic and relaxation shear tests on masonry with multi-layer bed joints are presented. • Rubber granulate core soft layer, protected by two thin elastomer layers was considered. • Model parameters are determined from authors' own tests. Abstract An analytical rheological model capable of describing the loading speed dependent in-plane shear behaviour of a masonry multi-layer bed joint is presented in this paper. Such joints consist of a core soft layer protected by two thin extruded elastomer membranes, which in turn are placed in a bed mortar joint. The extruded elastomer membranes are employed to prevent and/or limit the deterioration of the core soft layer during the cyclic action observed in previous investigations. Joint behaviour is assumed to be linear elastic-perfectly viscoplastic and has been captured by a uniaxial model consisting of three elements: an elastic spring connected in series with the frictional slider and a dashpot (viscous damper). The rheological model is characterized by three material parameters that have been assessed from several series of monotonic and static-cyclic tests on small masonry specimens (triplets). In addition to these three parameters, the contraction of the thickness of multi-layer bed joint due to pre-compression has been considered too. Although model parameters are determined for the multi-layer bed joint with a rubber granulate core soft layer, the parameter space can be extended to the other types of core soft layer once the appropriate test data becomes available. [ABSTRACT FROM AUTHOR]

Highlights • A damaging block-based model is proposed for the cyclic analysis of masonry structures. • Tests on small-scale specimens are used to calibrate the mechanical properties of the model. • In-plane, out-of-plane and full-scale cyclic tests on masonry structures are simulated. • A good agreement between the numerical results and the experimental outcomes is observed. Abstract In this paper, a damaging block-based model is proposed for the numerical analysis of the cyclic behaviour of full-scale masonry structures. Solid 3D finite elements governed by a plastic-damage constitutive law in tension and compression are used to model the blocks, while a cohesive-frictional contact-based formulation is developed to simulate their cyclic interaction. The use of tests on small-scale specimens to calibrate the mechanical properties of the numerical model is presented and discussed. The tests belong to a comprehensive experimental campaign performed on calcium silicate brick masonry. The calibrated models are used to simulate in-plane and out-of-plane cyclic tests on masonry walls made of the same material, as well as a quasi-static cyclic pushover test on a full-scale terraced masonry house. The efficiency, the potentialities and the accuracy of the model here proposed are shown and discussed. The capability of explicitly representing structural details (e.g. running bonds) and any in-plane and through-thickness texture of masonry, which appears essential to study the response of masonry structures, is guaranteed by the block-based modelling approach. A good agreement between the numerical results and the experimental outcomes is observed. This allows to validate the model in the cyclic response as well as the strategy proposed for its mechanical characterization. [ABSTRACT FROM AUTHOR]

Abstract: The present paper discusses the strength of unreinforced masonry subjected to in-plane loading. Applying the methods of the theory of plasticity, the state of stresses under investigation and compatible failure mechanisms are discussed and an extension (new regime) to an existing failure criterion for in-plane loaded masonry without tensile strength is given. This new regime takes into account slip failure along the head joints line which could be observed in compression tests and which could compromise the safety of the design based on the existing criterion. In addition, a novel proposal for the simplified variation of uniaxial masonry strength as a function of the angle of inclination of the principal compressive stress relative to the head joints direction is derived and proposed for practical applications. Further, the present paper gives an overview of an experimental program comprising the author’s own compression tests on wall elements made of concrete and calcium-silicate blocks as well as of clay brick masonry that was carried out at ETH Zurich. The results of these tests, together with those from further tests carried out by other researchers, have been used for the verification of the abovementioned proposal for the simplified variation of uniaxial masonry strength. A satisfactory agreement between the proposed simplification and test data has been found. [Copyright &y& Elsevier]

Graphical abstract Highlights • Application of basalt fibre mesh and cement mortar in flexural strengthening of URM. • Study of orientation of bed-joints and grid spacing of basalt fibre mesh. • Characterization of constituent materials including BFM and BFRCM. • Application of beam theory to predict the out-of-plane capacity of strengthened URM. • Identification of governing non-dimensional parameters to be used in design. Abstract This paper presents an experimental study on unreinforced masonry (URM) wallettes strengthened using basalt fibre mesh reinforced cement mortar (BFRCM) composite. A total of 8 URM and 16 strengthened wallettes, along with their constituent materials, were tested in two orthogonal directions, under two-point (line) out-of-plane loading. The variables examined in this study are loading direction and size of grid spacing of basalt fibre mesh. The performance of the strengthening technique is determined by examining failure modes, strength, effective rigidity, energy absorption capacity and ductility. A set of non-dimensional parameters is also defined for identifying the generalized behaviour of the wallettes. The strengthening technique using BFRCM enhanced the strength of the wallettes up to 4 times, deformability up to 29 times, and energy absorption capacity up to 139 times, as compared to URM wallettes. A comparison with analytical results shows that the ordinary beam theory predicts the strength with reasonable accuracy, but is not able to predict the effective rigidity. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Efficacy of strengthening using welded wire mesh (WWM) is established. • Effect of the orientation, shear span, and reinforcement ratio is studied. • Generalized parameters to compare results of different studies are proposed. • Simple beam theory shown to predict the moment capacity accurately. • Various failure modes of strengthened masonry are explained. Abstract This paper presents an experimental study on unreinforced masonry (URM) wallettes strengthened using welded wire mesh (WWM) reinforcement. A total of 8 URM and 28 strengthened wallettes along with their constituent materials are tested in two orthogonal directions, under two-point out-of-plane loading. The variables examined are loading direction, reinforcement ratio and effect of shear span. To compare the results of the present study with the past studies, six non-dimensional parameters are defined and examined for their suitability in identifying the generalized behaviour of the wallettes. The variation of non-dimensional parameters based on the geometric and material properties of the tested wallettes, in different studies is discussed. The strengthening technique enhances the flexural strength of the wallettes up to 9.4 times, deformability up to 61 times, and energy absorption capacity up to 1024 times, as compared to the URM wallettes. A comparison with analytical results shows that the ordinary beam theory predicts the flexural strength with reasonable accuracy. [ABSTRACT FROM AUTHOR]

• This paper presented the in-plane behavior of masonry walls strengthened with improved TRM. • The improved TRM composite can significantly improve the brittle failure to a ductile mode. • Bearing capacity of strengthened specimens were predicted based on different failure modes. • Two non-dimensional parameters were proposed to compare the efficiency of different TRM composites in literatures. Textile reinforced mortar (TRM) has been intensively researched over at last two decades. It is a composite consisting of textiles and inorganic matrix. The study presents an investigation on the diagonal compressive performances of unreinforced masonry (URM) walls strengthened with carbon and glass TRM composites which are added with short and water-dispersible polyvinyl alcohol (PVA) fibers. Ten specimens were designed to study the effect of the reinforcement configuration (single/double sides), layers of textiles and types of textiles on the in-plane behaviors of masonry walls under diagonal compression tests. It included a reference specimen, four single-side strengthened specimens and five double-side strengthened specimens. The failure mode, shear stress–strain response and deformation capacity of specimens were presented and discussed in this paper. The results showed that the improved TRM composites could improve the deformation and bearing capacity of masonry walls. The bearing capacity was predicted based on different failure modes of specimens. Furthermore, two non-dimensional parameters (α and β) were proposed to compare the efficiency and enhancement ratio of different TRM composites reported in literatures and this paper. It indicated that the improved TRM composites reached a considerable efficiency in improving the bearing capacity. [ABSTRACT FROM AUTHOR]

This paper introduces a single degree-of-freedom analytical model which has been used by the authors to investigate the out-of-plane performance of unreinforced masonry walls in vertical one-way bending subject to seismic actions. The objective of the modelling is to reduce costs on physical experimentation by supplementing and extending the limited experimental database on dynamic wall behaviour with analytical data. The procedure necessitates sufficient physical testing of specimens with representative boundary conditions to enable the analytical model to be calibrated against experimental results. A computer program which requires minimal data preparation effort and computational time has been written to conduct time–history analysis on the model. Importantly, key parameters have been incorporated in the program to facilitate calibration of the model. Details in developing representative tri-linear elastic force-displacement relationships and non-linear damping relationships to define the model are described in the paper. The developed model has been verified by comparing the computed acceleration and displacement response time-histories with results obtained from an extensive series of shaking table experiments. Seven of such time-history comparisons are shown in the paper to demonstrate the accuracy of the analytical model. [Copyright &y& Elsevier]

• Extensive experimental testing of unreinforced masonry behaviour under tensile and shear loads. • Probabilistic descriptions of the ratios between tensile and shear properties of unreinforced masonry. • Presentation of raw experimental data. • Consideration of the effects of net-section and stress-raisers for perforated masonry units. This paper presents the results of an extensive set of material characterisation tests performed on unreinforced clay brick masonry. The results of these experiments allow for the estimation of relationships between the measured material parameters. This study considers the relationships of flexural tensile bond strength to direct tensile bond strength, flexural to direct tensile strength of fired clay brick masonry units, and flexural tensile to shear bond strength. A mean ratio of flexural tensile bond strength to direct tensile bond strength of 2.06 and a COV of 31.5% were determined. For the flexural to direct tensile strength of fired clay brick masonry units, a mean ratio of 1.29 with a COV of 14.7% was estimated. Finally, considering the ratio of the shear bond to flexural tensile bond strengths, a mean ratio of 1.34 with a COV of 28.4% was found. In addition to these relationships, suitable probabilistic models were determined to describe the relationship between the flexural and direct tensile bond strengths, and the flexural tensile and shear bond strengths. These results may be used in future studies of URM structures, in particular finite element modelling and stochastic analyses of masonry. [ABSTRACT FROM AUTHOR]

The paper investigates the energy- and amplitude-dependent natural periods of symmetrically cracked semi-circular arches, which are loaded by their self-weight and horizontal support displacement. The cracks appear due to previous static effects. Symmetric free vibration of the arches is under analysis. The symmetry condition results in an SDoF system, but the latter purpose of the authors is to analyse nonsymmetric modes with an MDoF model. To analyse the problem an energy-based approach is developed. The motion of a structure consists of states with nonlinear vibrations, each of which has constant energy content. Between these phases inelastic impacts occur, which have effect only on the velocity field, but have no effect on the displacements, because the time duration of the impacts is assumed to be zero. In the work the position of the cracks and other geometrical parameters are under examination and the energy-, amplitude- and support displacement magnitude-dependent natural periods are obtained. These results may help to monitor the historical buildings structural safety, because with the measured natural period and amplitude one can determine the safety of the structure. [ABSTRACT FROM AUTHOR]

In this paper, we explore the potential of convolutional neural networks to classify street-level imagery of one-story unreinforced masonry buildings (MURs) according to the flexibility of the roof diaphragm (rigid or flexible). This information is critical for vulnerability studies, disaster risk assessments, disaster management strategies, etc., and is of great relevance in cities where unreinforced masonry is the most common building typology or where the majority of the population resides in such buildings. Our contribution could be useful for local governments of cities in developing countries seeking to significantly reduce the number of deaths caused by disasters. Our research results indicate that VGG19 is the convolutional neural network architecture with the best performance, with an accuracy of 0.80, a precision of 0.88, and a recall of 0.84. The results are encouraging and could be used to reduce the amount of resources (both human and economic) for the development of detailed exposure models for unreinforced masonry buildings. • This paper focuses on one-story unreinforced masonry buildings. • One-story unreinforced masonry buildings are vulnerable to seismic loads. • Unreinforced masonry represents 31% of the residences of the Andean region. • We use neural networks to classify the roof diaphragm flexibility of buildings. • Our model has an accuracy of 0.80, a precision of 0.88, and a recall of 0.84. [ABSTRACT FROM AUTHOR]

This paper describes a methodology for modelling the nonlinear, inelastic load–displacement behaviour of two-way spanning unreinforced masonry walls subjected to out-of-plane loading. The model utilises a simplified macroblock approach that starts with the assumption of a collapse mechanism based on the wall’s boundary conditions. It then treats the wall as having zero tensile strength and assumes that the resistance comes entirety from two gravity-based resistance components: elastic rigid block rocking, and inelastic friction, with the total load resistance of the wall taken as the sum of these individual components. Analytical expressions for calculating the load and displacement capacities of the elastic rocking component of response are derived from the principles of statics using an integration approach well suited for the treatment of two-way mechanisms. Expressions for the associated frictional capacity component are obtained using the virtual work method. Comparison of the theoretical load–displacement response with experimentally measured data is favourable as demonstrated using data obtained via quasistatic cyclic tests on two-way spanning walls; the model is shown to provide an acceptable lower bound estimate of actual behaviour. The developed approach could be used to construct pushover curves for a range of different collapse mechanisms and therefore has the potential to be assimilated into a simplified displacement-based seismic design/assessment technique for two-way spanning walls against out-of-plane collapse. [ABSTRACT FROM AUTHOR]

• Unreinforced masonry (URM) systems although are typically not earthquake-resistant. • A possible strategy is to increase the ductility of URM system through the mortar. • The research program "ZERO" developed and tested a ductile mortar for URM systems. • The results evidenced improved strength and ductility of the overall masonry system. The paper presents the results of an experimental campaign aimed at assessing the structural performances of unreinforced masonry systems realized with a novel ductile mortar. The experimental campaign described in the paper is part of the research project "Zero Environmental Risks in Our buildings" (ZERO) whose broad objective is to develop a new class of construction materials and decorative products characterized by high environmental compatibility, i.e. Volatile Organic Compounds (VOC)-free, as well as superior performances in terms of both chemical and mechanical properties. Two mortar formulations, one for thin-joints and one for thick-joints, have been tested under flexural and compressive loads, and their performances compared with those of benchmark mortars available in the market. Masonry assemblies have been realized with different types of hollow clay blocks available in the market, including flat structural and non-structural blocks for thin joints and structural clay blocks for ordinary joints. The results of the experimental tests proved the effectiveness of the innovative ductile mortar in improving both shear strength and shear deformation capacities of unreinforced masonry assemblies. [ABSTRACT FROM AUTHOR]

The paper describes the evaluation of seismic capacity of the unreinforced masonry building in the high seismic zone by an analytical procedure, based on nonlinear static approach. In this procedure, each wall plane is modeled as some vertical strip walls separated by the openings and is characterized by two primary components such as vertical component pier and horizontal component spandrel. These walls are analysed considering the capacity of pier in conjunction with the coupling effect between pier and spandrel. However, capacity of spandrel is not considered in this case. The shear capacity of the wall is calculated based on lower bound theorem of plasticity without considering the tensile strength of masonry. Capacity curves of the walls are determined by three parameters as shear capacity, yield displacement and ultimate displacement at zero stiffness approaching a bilinear approximation and these capacity curves of the walls in a certain orthogonal direction are superposed to obtain capacity curve of the building in that direction. The smaller capacity of the building in the prevalent direction is then compared with seismic demand and a capacity-demand relationship is found and damages are introduced in this capacity-demand relationship to obtain vulnerability function. The vulnerability function of the representative masonry building models are used to construct fragility function of the building group and this fragility function shows the expected damage of the building group as a function of spectral displacement. [ABSTRACT FROM AUTHOR]

A significant number of macroscopic constitutive models is available to simulate the behaviour of unreinforced masonry (URM) in compression, but they produce different predictions of sectional response to eccentric compressive loading. In this paper, nonlinear moment–curvature analysis of rectangular URM cross sections is presented to explore the influence of alternative constitutive models and ultimate limit state assumptions in terms of post-peak strength degradation and strain ductility. Theoretical moment–curvature diagrams are quantitatively compared to experimental data at multiple levels of load eccentricity through goodness-of-fit measures. Different constitutive models are found to produce a good simulation of experimental moment–curvature behaviour, depending on whether experimental data are disaggregated in terms of masonry type or not. Moment–curvature diagrams are derived by keeping constant either the magnitude or the eccentricity of axial load. Finally, the effects of tensile properties and model error of theoretical moment–curvature diagrams are assessed. [ABSTRACT FROM AUTHOR]

This paper proposes a model for simulating the dynamic behaviour of slender external walls of unreinforced masonry buildings with flexible diaphragms subjected to out-of-plane bending. The proposed model is characterized by two degrees of freedom (2DOF) and allows to perform time-history analyses in order to study the influence of diaphragm flexibility on the displacement capacity and demand of walls in out-of-plane bending. The wall has been modelled as an assemblage of two rigid bodies connected by an intermediate hinge and restrained at the top by a spring: the damping has been modelled through the introduction of the coefficient of restitution. The equations of motion of the 2DOF system have been derived and integrated in the time domain. Dynamic analyses of a set of walls subjected to Gaussian impulses and recorded ground motions have been performed in order to compare the response of the simply supported wall with that of the wall with an elastic spring at the top. [ABSTRACT FROM AUTHOR]

A research project on the displacement capacity of contemporary unreinforced masonry (URM) walls is underway at the Institute of Structural Engineering of ETH Zurich. The development of the basis for the displacement-based design of URM structures is the prime objective of the present project. In the experimental phase of the project, a total of 10 static-cyclic shear tests on full-scale URM walls made of clay and calcium-silicate blocks were performed to investigate the effects of various factors, i.e. unit type, vertical pre-compression level, aspect ratio, size, and boundary conditions, on the displacement capacity of URM walls. This paper presents and discusses the obtained test results. All the walls (regardless of their failure mode) exhibited limited displacement capacity. The test results show that as the vertical pre-compression level increases, the displacement capacity decreases. Furthermore, they indicate a possible reduction in the displacement capacity of URM walls in the case of an increase in the height or a decrease in the aspect ratio, i.e. the height divided by the length. It is also shown that the values recommended by the current codes of practice for the displacement capacity of URM walls cannot be considered as reliable. Finally, a simple empirical model for the displacement capacity of contemporary URM walls is proposed, based on the results obtained from the tests. [ABSTRACT FROM AUTHOR]

[Display omitted] In this paper, the in-plane flexural drift capacity of masonry walls is numerically investigated. In particular, a nonlinear truss-based model is specifically developed to predict the monotonic response of in-plane horizontally-loaded masonry walls undergoing flexural failure, so that to investigate their deformation capacity. This novel modelling strategy assumes a band of nonlinear truss elements at the wall toe to account for flexural failure. The truss elements are supposed no-tension with plastic-softening behaviour in compression. This simple and original model is easily and fully characterizable by experimentally-based compressive stress–strain relationships available in the literature for different masonry types. The modelling strategy is validated against two different pier-scale experimental tests which experienced flexural failure. The model is then used to predict the flexural drift capacity of walls with different masonry types and geometrical features, subjected to a full-range of axial load ratios. As a result, drift capacity is found to nonlinearly decrease while increasing the axial load ratio, and to be sensibly dependent on the wall width (i.e. drift capacity diminishes while increasing wall width), for any masonry type. Finally, a simple analytic expression based on numerical results is deduced for the flexural drift capacity of masonry walls, function of axial load ratio, masonry type, and wall size. Accordingly, this analytic expression could be implemented in any structural analysis masonry-oriented commercial code to account for a consistent description of the flexural drift capacity of masonry walls. [ABSTRACT FROM AUTHOR]

• Monte-Carlo experimental investigations of 18 full-scale URM veneer wall systems. • Wall ties under monotonic and semi-cyclic compression and tension loading. • Mortar bond strength statistics and batch to batch variabilities investigated. • True variabilities were evaluated considering test errors and workmanship. • Higher variabilities observed for the wall system under outward (tension) loading. This paper presents the results of a probabilistic experimental study into the behaviour of full-scale unreinforced masonry (URM) veneer walls with flexible backup subjected to out-of-plane loading. The actual safety and reliability of the contemporary Australian URM structures are unknown due to the absence of information regarding the probabilistic behaviour of the whole veneer wall system and material characterisation of the wall constituent materials. The study focused on masonry typologies representative of modern URM buildings in the Australian context. In this study, 18 full-scale URM veneer wall systems with theoretically identical geometries and properties were tested under inward and outward out-of-plane loading. For each loading type, one specimen was tested under semi-cyclic loading to check whether the monotonic loading can capture the overall behaviour of the cyclic response. For each mortar batch mixed, bond wrench testing was conducted at the same age as the test for the associated wall constructed using that mix. Batch to batch variabilities were statistically analysed, and probability distributions for flexural tensile strength were established. Lognormal distributions with aggregated means of 0.40 MPa and 0.42 MPa for inward and outward loading, respectively, were estimated for flexural tensile strengths. After the wall tests, all timber studs used to build the veneer walls were tested to evaluate the probabilistic characterisation of timber stiffness. This probabilistic information is essential for a stochastic finite element analysis (FEA) to conduct the reliability analysis. From the wall tests, veneer wall system behaviour was observed and measured until the collapse or 20% post-peak drop of the peak load. Outward loaded specimens exhibited higher variabilities for masonry cracking and system peak load compared to inward loading due to variabilities from materials, testing arrangements and failure mechanism. The true coefficient of variations of system peak loads were calculated as 0.10 and 0.19 for inward and outward loadings, respectively, considering the effect of testing variability. [ABSTRACT FROM AUTHOR]

• The in-situ brick shove test is experimentally benchmarked against the couplet test. • A simpler in-situ 'pull test' is also trialled, loading the brick out-of-plane. • For plain bricks, shove and pull tests are slightly conservative relative to couplet. • For frogged bricks, both in-situ tests overestimate shear strength relative to couplet - Selection of in-situ approach needs to reflect the intended end-use of test data. For other than minor modifications or additions to existing masonry structures, an understanding of the in-situ mechanical properties of the masonry is required. Estimation of shear strength of the masonry bond is often made using the in-plane shove test as it only requires access from one side of the masonry being tested, and is therefore considered to be only mildly invasive. In-situ and laboratory simulations of the shove tests have however shown that a number of site-specific problems can arise. These include: preparation of the test area which can damage the mortar joints resulting in loss of cohesion, imprecise alignment of both the loading system and instrumentation leading to complications with data interpretation, and without an adequately long section of wall to be tested, flexural cracking and lateral displacement of large wall sections. In an attempt to address these issues, in this paper, an alternative in-situ test is proposed. This new ' pull test' measures shear strength by extracting a single brick orthogonally in the wall's out-of-plane direction. A laboratory investigation is performed to compare the two types of in-situ test (shove and pull) using plain and frogged units, as well as lime and cement mortars, and both tests are further benchmarked using the standard laboratory couplet test. It is demonstrated that for regular (rectangular), plain units with weak mortar, the two in-situ tests produce strength measurements that are statistically equivalent, indicating that under this specific scenario the out-of-plane shear strength can be used as a proxy for the in-plane shear strength, and that the pull test could be used as an alternative to the shove test. In addition, the new pull test is shown to perform with demonstrated repeatability, requires minimal instrumentation, and is particularly relevant for design of anchorages under out-of-plane loading. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical behaviour of unreinforced masonry cross sections subjected to eccentric compressive loading has been studied through laboratory tests, analytical procedures, and numerical models. Several macroscopic constitutive models have been implemented in beam-like analytical approaches in order to derive axial force – bending moment limit domains. This paper investigates the influence of different macroscopic constitutive models and strain softening on the strength domain evolution from the elastic limit state to the ultimate limit state. Simplified equations are proposed for the Eurocode 6 constitutive model and strength-degrading stress–strain relationships. The corresponding limit strength domains and those derived from other constitutive models are compared to experimental data available in the literature. It is shown that more conservative estimates of ultimate moment capacity are obtained if some of the proposed equations, or those corresponding to the elastic-perfectly brittle constitutive model, are used. Finally, evolutionary strength domains defined in a dimensionless axial force – bending moment – strain ductility space were developed to investigate how bending moment capacity changes with masonry ductility in compression. Such domains could be implemented in equivalent frame models to simulate moment capacity variations with deformation demands on individual macro-elements as static pushover analysis proceeds. [Copyright &y& Elsevier]

Abstract: Sensitivity Analysis (SA) has very important implications in terms of model assessment. It is an important part of reliability studies as well. This paper presents global SA using High Dimensional Model Representation (HDMR) on a mesoscale model of unreinforced masonry shear wall. The mesoscale model contains both geometric as well as material nonlinearity. Prior to performing global SA: (a) mesh sensitivity study in order to determine the optimum mesh size; and (b) experimental validation of the finite element simulation using the data available in the literature, are conducted. The ability of two major variations of HDMR, namely RS (Random Sampling)-HDMR and Cut-HDMR, for conducting global SA is explored, first by solving analytical problem and later by analyzing the mesoscale model of unreinforced shear wall. From the study, recommendations are made to obtain the sensitive parameters of an unreinforced masonry structure with minimal computational effort. [Copyright &y& Elsevier]

Abstract: In this paper, a numerical model for the pushover analysis of in-plane loaded unreinforced masonry walls is presented. For the analysis of the walls, which consist of vertical piers connected by horizontal masonry spandrels, an equivalent frame model is adopted. The analysis approach consists of two steps: In Step I, ultimate bending moment-shear force strength domains of the masonry spandrels are derived by means of a heterogeneous upper bound FE limit analysis and the results are stored in a database. Assessing the capacity of the spandrels correctly is crucial for the ultimate resistance of masonry walls that are loaded in-plane. Heterogeneous limit analysis is particularly suitable for computing the failure load of unreinforced masonry members since it permits a distinct modelling of bricks and mortar joints. Appropriate static and kinematic boundary conditions are imposed to account for the complex interaction of internal forces and deformed shapes of the spandrel beams at failure. In Step II, a frame model of the masonry wall is assembled. In this frame model the spandrels are modelled as elastic Timoshenko beams. At each analysis step it is checked that the internal forces of these coupling beams are smaller than the failure loads stored in the database created in Step I. If the capacity is exceeded, flexural hinges are introduced at both ends of the coupling beam. The resistance of the element is set to zero when a limit chord rotation is exceeded. The piers are modelled in a similar manner. The shear force and bending moment capacity of the piers are, however, simply estimated according to the Italian Design Code. Pushover analysis results compare favourably with computationally expensive 2D nonlinear heterogeneous FE analyses, but also confirm that the ultimate lateral resistance of masonry walls is very sensitive to the assumed spandrel strength if an equivalent frame model is used. [Copyright &y& Elsevier]

Abstract: The out-of-plane bending and in-plane shear response of unreinforced modern clay brick masonry walls retrofitted with fibre-reinforced polymer (FRP) strips is often governed by debonding failure mechanisms. Hence, it is necessary to quantify the fundamental interface bond–slip model, which describes the debonding behaviour of the FRP-to-masonry interface. This paper presents the results of a series of 29 pull tests investigating the use of externally bonded (EB) and near surface mounted (NSM) retrofitting techniques. Test variables included: surface preparation; geometric properties; location of FRP (relative to perpend joints and cores); bonding agent of bed joints (mortar and quick drying paste); bonding method for glass fibre sheets (plate bonding and dry lay-up); and FRP material. A discussion of the test results and preliminary practical recommendations are also provided. A model used to predict the intermediate crack debonding resistance was verified against the test data. The model is generic in that it is applicable to both the EB and NSM retrofitting techniques. This generic model was shown to give very good ultimate strength predictions for the series of 29 pull tests conducted as part of this research. [Copyright &y& Elsevier]

Abstract: Unreinforced masonry (hereafter termed ‘masonry’) structures comprise a significant proportion of the building stock in many countries worldwide, however their walls do not behave well under out-of-plane loading, such as that experienced during seismic events. Consequently, many existing masonry structures require some form of retrofit to comply with existing codes. As part of ongoing research at The University of Adelaide on the out-of-plane bending behaviour of masonry walls, eight full-scale walls (with window openings) were tested under reversed-cyclic loading. Four of the severely damaged walls were subsequently retrofitted using externally bonded (EB) (three walls) and near-surface mounted (NSM) (one wall) fibre-reinforced polymer (FRP) strips and tested again to quantify the increase in strength and ductility relative to the original capacities. A debonding mechanism not yet quantified for retrofitted masonry walls was observed and identified as displacement induced (DI) debonding. It is a result of a differential out-of-plane displacement at either side of a crack in the wall. NSM strips are more susceptible due to their orientation. This paper presents the results of the wall tests along with detailed accounts of the wall failure modes. [Copyright &y& Elsevier]

Abstract: In this paper a novel equivalent planar-frame model with openings is presented. The model deals with seismic analysis using the Pushover method for masonry and reinforced concrete buildings. Each wall with opening can be decomposed into parallel structural walls made of an assemblage of piers and a portion of spandrels. As formulated, the structural model undergoes inelastic flexural as well as inelastic shear deformations. The mathematical model is based on the smeared cracks and distributed plasticity approach. Both zero moment location shifting in piers and spandrels can be evaluated. The constitutive laws are modeled as bilinear curves in flexure and in shear. A biaxial interaction rule for both axial force–bending moment and axial force–shear force are considered. The model can support any shape of failure criteria. An event-to-event strategy is used to solve the nonlinear problem. Two applications are used to show the ability of the model to study both reinforced concrete and unreinforced masonry structures. Relevant findings are compared to analytical results from experimental, simplified models and finite element models such as Drain3DX and ETABS finite element package. [Copyright &y& Elsevier]

• Assessing the seismic response of the wall tie connections in cavity walls. • Proposing a mechanical model for the wall tie connections. • Considering six possible failure modes of the cavity wall ties. • Performing parametric analyses to asses the influence of several key parameters. The seismic assessment of unreinforced masonry (URM) buildings with cavity walls is a relevant issue in many countries, such as in Central and Northern Europe, Australia, New Zealand, China and several other countries. A cavity wall consists of two separate parallel masonry walls (called leaves) connected by metal ties: an inner loadbearing wall and an outer veneer having mostly aesthetic and insulating functions. Cavity walls are particularly vulnerable structural elements. If the two leaves of the cavity wall are not properly connected, their out-of-plane strength may be significantly smaller than that of an equivalent solid wall with the same thickness. The research presented in this paper focuses on a mechanical model developed to predict the failure mode and the strength capacity of metal tie connections in masonry cavity walls. The model considers six possible failures, namely tie failure, cone break-out failure, pull-out failure, buckling failure, piercing failure and punching failure. Tie failure is a predictable quantity when the possible failure modes can be captured. The mechanical model for the ties has been validated against the outcomes of an experimental campaign conducted earlier by the authors. The mechanical model is able to capture the mean peak force and the failure mode obtained from the tests. The mechanical model can be easily adopted by practising engineers who aim to model the wall ties accurately in order to assess the strength and behaviour of the structures against earthquakes. Furthermore, the proposed mechanical model is used to extrapolate the experimental results to untested configurations, by performing parametric analyses on key parameters including a higher strength mortar of the calcium silicate brick masonry, a different cavity depth, a different tie embedment depth, and solid versus perforated clay bricks. [ABSTRACT FROM AUTHOR]

The paper describes the derivation of fragility curves useful for the seismic risk analyses of existing unreinforced masonry buildings inserted in aggregate. The L-shaped examined aggregate consists of three adjacent structural units that may mutually interact during seismic events. The seismic assessment is focused on the corner unit. The effects of different connection types between the adjacent units on the structural response were investigated. The seismic vulnerability of the masonry aggregate was assessed through nonlinear dynamic analyses (NDA) performed according to the multi-stripes approach. Both the in-plane and out-of-plane mechanisms were analyzed. The in-plane response of the corner unit is assessed through a 3D equivalent frame model of the entire aggregate, while the evaluation of its out-of-plane response makes use of the rigid-block assumption. Although evaluated in a separate way, the NDAs performed on the latter are based on the time histories derived from the global 3D model. The results are then processed in order to derive fragility curves, firstly, of the single failure mechanisms and, then, of the overall combined behavior. To this aim, various performance conditions are examined. For the reference building, the damage limit state is mainly governed by the in-plane behavior, while the collapse limit state by out-of-plane mechanisms. Moreover, the higher the connection level between adjacent structural units, the higher the interaction between in-plane and out-of-plane mechanisms at the collapse limit state. • Procedure for derivation of fragility curves by NLDA accounting for both in-plane and out-of-plane mechanisms. • The 3D equivalent frame model of the aggregate considers the interaction between buildings by proper joints. • Rigid block NLDAs of the OOP response use time histories derived from the 3D model of the aggregate. • For the corner building, damage limit state is governed by IP response while collapse by OOP mechanisms. • The higher the connection between structural units, the higher the interaction of IP and OOP at collapse. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a numerical formulation for the analysis of unreinforced masonry walls under shear–compression fracture. To achieve this, the formulation of Attard and Tin-Loi [Attard MM, Tin-Loi F. Numerical simulation of quasibrittle fracture in concrete. Engineering Fracture Mechanics 2005;72:387–411] used for the simulation of fracture in concrete has been extended to model unreinforced masonry and enhanced by including a compression cap in the failure surface. The finite element formulation is based on a triangular unit, constructed from constant strain triangles, with nodes along its sides but not at the vertex or the center of the unit. Fracture is modeled through a constitutive softening-fracture law at the boundary nodes. The constitutive law is a single branch softening law. The material within the triangular unit remains linear elastic. Triangular units are grouped into rectangular zones which mimic brick units and mortar joints. The path-dependent softening behaviour is solved using a linear complementarity problem (LCP) formulation, in non-holonomic rate form within a quasi-prescribed displacement approach. The inelastic failure surface is modeled using a Mohr–Coulomb failure surface with a tension cut-off and a linear compression cap. The formulation is verified by comparing the results with available experimental and numerical results on shear walls under shear compression loading. [Copyright &y& Elsevier]

• Two-step automated procedure for the seismic assessment of masonry structures. • Utilization of adaptive upper bound NURBS limit analysis and pushover with CDP in Abaqus. • Procedure working under in-plane and combined in- and out-of-plane loading conditions. • Cohesive-frictional contact-based interfaces are used in step2 with masonry crushing allowed. • The effectiveness of the procedure is shown on a 3D full-scale masonry building. In this paper, a two-step automated procedure based on adaptive limit and pushover analyses is developed for the seismic assessment of masonry structures. Inspired by an akin procedure previously developed by the authors for the out-of-plane behaviour, the procedure herein presented is extended to in-plane and combined in- and out-of-plane loading conditions, accounting also for the effect of masonry crushing failure. In the first step, an upper-bound adaptive limit analysis tool is used to predict the collapse mechanism (and the corresponding multiplier) of the structure given a certain loading condition. A novel ad-hoc routine is then developed and utilized for the automatic import of the collapse mechanism geometry of any complexity into a solid model ready to be used in a finite element framework. In the second step, cohesive-frictional contact-based interfaces are automatically inserted in the cracks of the collapse mechanism formerly obtained, and a pushover analysis is conducted to investigate the load–displacement response of the structure. A series of parametric analyses are conducted to highlight the effect of different mechanical assumptions. Finally, the effectiveness of the procedure proposed is shown on a full-scale masonry building case study. [ABSTRACT FROM AUTHOR]

• A review of low-processed scrap tires in civil engineering applications is presented. • Retaining, seismic retrofitting, load bearing and drainage applications are discussed. • Scrap tire is a cost-effective construction material. • Low-tech scrap tire applications can be used in disaster risk reduction projects. • The reviewed applications are particularly suitable for low-resource communities. The mechanical properties of waste tires make them an interesting secondary raw material for a wide range of civil engineering applications. Employing whole scrap tires (WSTs) and low-processed scrap tires (LPSTs, i.e. scrap tires that have not been processed by industrial machineries) as a repurposed construction material is a high-value recovery option that requires less resources and energy than recycling. Researchers and practitioners around the world have been able to develop a significant number of innovative and promising WST and LPST applications, particularly for disaster risk reduction (DRR) projects and in vulnerable communities with limited resources. This paper provides a literature review of the current state of the art for the use of WST and LPST in civil engineering applications (CEAs) within the context of DRR. Four main categories of CEAs have been identified according to the primary function of the scrap tire applications presented: earth retaining structures, seismic retrofitting applications, load-bearing elements, and drainage systems. The available studies have been organized, classified and discussed in order to take stock of a heterogeneous field of research and highlight areas where further research is needed. [ABSTRACT FROM AUTHOR]

• Spatial stochastic finite element analysis of out-of-plane loaded masonry walls. • Inclusion of unit-to-unit spatial correlation of flexural tensile bond strength. • Peak pressure load is compared to test results, showing good agreement. • Simulations used to assess effect of length on peak pressure and COV. • Length effect is represented accurately using partial plasticity hypothesis. The strength of unreinforced masonry (URM) walls subjected to one-way vertical bending under out-of-plane loading (no pre-compression) is known to be affected by the tensile bond strength. Factors such as batching, workmanship, and environmental exposure alter the strength of this bond, resulting in spatial variability for any URM assembly. In narrow wall panels a single weak joint may dictate the failure load of a masonry wall, whereas for longer walls there is higher potential for weak joints to occur and load redistribution. This paper focuses on a stochastic assessment of clay brick URM walls with spatially variable tensile bond strength subjected to uniformly distributed out-of-plane loads in one-way vertical bending and assessing the effect of wall length on the ultimate failure load. Stochastic computational modelling combining 3D non-linear Finite Element Analysis (FEA) and Monte Carlo Simulation (MCS) is used to account for bond strength variability when estimating the walls ultimate failure loads. For this assessment FEA MCS has been applied to a set of existing test data for walls 1, 2, 4, and 10 units long, by ten different masons. Models were also developed to consider walls in the intermediate length range, 7 units long, and walls outside of this range, 15 units long. For each set of simulations the peak pressure and load–displacement data was extracted and analysed, showing agreement with the results of wall test data. The panel strength is shown to increase with wall length from 1 to 4 units, then stabilize with further length increase. The variability of the failure load is shown to decrease with increasing wall length. [ABSTRACT FROM AUTHOR]

• Stochastic FE modelling of masonry walls subject to in-plane shear loading. • Consideration of spatial variability of properties. • Peak load capacity and cracking consistent with experimental testing. • Monotonic load applied to models representative of cyclic envelope of load effects. • Ratio of the direct and flexural tensile strengths of masonry units discussed. • Ratio of the direct and flexural tensile strengths of unit-mortar bond discussed. This paper develops a modelling strategy for the finite element analysis of perforated (arched) unreinforced masonry walls subjected to in-plane shear loading. An experimental baseline was used to facilitate an accurate calibration and assessment of the chosen modelling strategy. This study provides the procedure and the results relevant to a stochastic assessment of unreinforced masonry shear walls. These results may be used in future studies of the reliability of these structures and may be applied in the calibration of reliability-based design practices. Utilising a two-dimensional micro-modelling approach, the capacity of a monotonic loading scheme to capture the envelope of a cyclically applied load was examined. It was found that, while the elastic stiffness of the laboratory specimens was overestimated by the finite element models, the peak load and global response was accurately recreated by the monotonically loaded models. Once the applicability of this procedure had been established, a series of spatially variable stochastic finite element analyses were created by considering the stochastic properties of key material parameters. These analyses were able to estimate the mean load resistance of the experimentally tested walls with a greater accuracy than a deterministic model. Furthermore, these analyses produced an accurate estimate of the variability of shear capacity of and the observed damage to the laboratory specimens. Due to the fact that the tested walls failed almost exclusively in a rocking mode, a failure mechanism highly dependent upon the structures' geometry, the variability of the peak strength was minimal. However, the observed damage and presence of some sliding and stepped cracking indicates that the proposed methodology is likely to capture more variable and unstable failure modes in shear walls with a smaller height-to-length ratio or those more highly confined. [ABSTRACT FROM AUTHOR]

• A Summary of typical seismic performance and failure modes of massive URM buildings. • A Summary of typical seismic behavior and failure mechanisms of URM bell-towers. • Overview of the September 19, 2017 (M w = 7.1) Puebla-Morelos EQ and seismic risk. • Observed damage description in URM buildings in Puebla, Morelos and Mexico City. • Practical applications of seismic rehabilitation/retrofitting of damaged Churches. Unreinforced masonry is one of the main construction materials used in the edification of most historical buildings around the world. This is due to its availability in nature, low-cost benefits and durability. Churches and bell towers were built to mainly withstand vertical loading induced by self-weight, disregarding the lateral performance mainly by the limitations of masonry. These massive structures present poor seismic performance due to the low tensile strength of masonry, lack of structural integrity, elevated seismic forces and heterogeneity. The last plays an important role in the in-plane and out-of-plane behavior/failure by anisotropy. This paper is aimed at presenting post-earthquake investigations in damaged Churches and bell towers by the September 19, 2017 (M w = 7.1) Puebla-Morelos Earthquake which damaged thousands of historical buildings. These buildings presented partial and total collapses in façades, domes, vaults, arches and bell towers. The structural vulnerability, combination of materials, large openings and reduced vertical loading at top parts of belfries induced a rapid propagation of heavy damage which ended in brittle collapses. The widespread damage was induced by the missing compatibility of deformations and integrity among structural elements/materials and previous damages. These post-earthquake observations are aimed at identifying the behavior/failure of these buildings to propose practical intervention measures. The most suitable retrofitting materials/strategies were identified as practical applications for walls, bell towers, domes, vaulted covers and timber roofs/slabs to increase the displacement/strength capability by inducing more ductile failure with increased EQ energy dissipation through the enhanced hysteretic behavior. [ABSTRACT FROM AUTHOR]

• Bed joint reinforced repointing is investigated experimentally & numerically. • In-plane stiffness & capacity are increased by bed joint reinforced repointing. • Bed joint reinforced repointing causes out-of-plane effects during in-plane loading. The province of Groningen in the Netherlands is experiencing the continuous impact of gas extraction in the form of induced seismicity. Due to the absence of naturally occurring seismicity in the region, the historic building stock of Groningen was constructed without empirical design features typically encountered in naturally seismic regions. Further, gas extraction, in combination with soft topsoil, is responsible for substantial amounts of ground subsidence. This subsidence may compromise the capacity of existing structures to bear seismic loading. Historic masonry structures, particularly those lacking traditional earthquake-resistant features, are vulnerable to seismic loads. Further, their substantial weight, in-plane stiffness, low tensile strength and brittleness renders them vulnerable to settlement-induced damage. Given the cultural significance of architectural heritage, the performance of historic buildings in the Damage Limitation (DL) state is a matter of importance. Additionally, due to the incorporation of both vernacular and monumental architectural heritage buildings in the urban setting, their performance in the Near Collapse (NC) state is as important as that of ordinary building structures. Therefore, methods and techniques for enhancing the behaviour of historic buildings in both States need to be devised and evaluated. This paper focuses on the application and assessment of a retrofitting technique commonly used for damage prevention and repair in unreinforced masonry structures in the Netherlands, namely bed joint reinforced repointing. The technique consists in the embedment of stainless-steel bars in continuous bed joints, as well as their dry placement across cracks in the masonry. The technique is applied on a masonry wall tested under quasi-static cyclic in-plane shear loading for the evaluation of its performance not only in the DL state for which it was conceived, but also in the NC states. The wall features artificially introduced cracks that simulate settlement-induced damage prior to the installation of the bars. A finite element meso-model is used for the simulation of the wall tests, featuring the artificial damage and reinforcement elements. The model is used in non-linear cyclic analyses for the simulation of the experiments. Through experimental testing and numerical modelling, the efficiency of the strengthening technique is evaluated in terms of resulting shifts in wall capacity, stiffness and failure mode. Further comments are provided concerning its applicability and structural compatibility. [ABSTRACT FROM AUTHOR]

• Novel 3D macroelement approach for nonlinear simulation of masonry components. • Accurate representation of complex failure modes under cyclic loading. • Nonlinear cohesive-frictional interfaces describe the interaction between adjacent deformable blocks. • Enhanced kinematics to represent out-of-plane bending response. • Model validation via comparison with results from physical experiments. The paper presents a novel 3D macroelement approach for efficient and accurate nonlinear analysis of unreinforced masonry components subjected to in-plane and out-of-plane cyclic loading. A macroscopic description for masonry is employed, where macroelements, consisting of deformable blocks interacting through cohesive interfaces, are used to represent large portions of masonry walls, enhancing computational efficiency. Enriched kinematic characteristics are adopted for the homogeneous blocks, where in-plane shear and out-of-plane bending modes are described by two independent Lagrangian parameters. Moreover, a detailed material model for the nonlinear interfaces connecting adjacent elements enables an accurate representation of complex failure modes and cracking patterns in masonry walls. As a result, the proposed FE strategy can be employed for accurate response predictions of large masonry structures subjected to cyclic loading conditions. The accuracy of the macroelement approach is validated through comparisons against results of experimental tests of solid and perforated masonry walls under in-plane and out-of-plane loading. [ABSTRACT FROM AUTHOR]

• Dynamic testing of full-scale URM walls in the OOP (two-way bending) direction. • URM wall subjected to simultaneous vertical and OOP seismic excitation. • Formulation to evaluate initial stiffness of URM walls under OOP excitation. This paper presents the results of incremental dynamic tests on full-scale unreinforced masonry (URM) walls constructed with an intentionally weakened mortar under two-way bending excitation in the out-of-plane (OOP) direction. A specimen was also subjected to simultaneous vertical and horizontal excitation. Walls were also tested in boundary conditions that have not been previously reported in the literature. Emphasis was placed on the development and interpretation of a characterisation test to estimate the torsional shear strength of bed-joints, a parameter of prime importance in the OOP two-way bending behaviour of URM walls. Analytical formulation to estimate the initial stiffness of walls based on the theory of plates is then proposed and validated. Being the first experimental campaign to address the dynamic OOP two-way bending response of full-scale URM wall panels provided the opportunity to propose simple yet mechanically rational methodologies with which both the peak force resistance as well as the displacement at which such resistance is attained can be easily estimated. [ABSTRACT FROM AUTHOR]

• Simplified macro-modeling approaches are practical and promising methods. • Nonlinear behavior of irregular unreinforced masonry building. • Elastic modulus might be a model parameter rather than material parameter. • Combined in-plan and out-of-plane behavior on modern masonry buildings. • Equivalent frame model is conservative relative to other approaches. The present paper addresses the seismic performance of a half-scale two-story unreinforced masonry (URM) building with structural irregularity in plan and in elevation. The main objectives are (i) to understand the seismic response of URM buildings with torsional effects, and (ii) to evaluate the reliability of using simplified approaches for irregular masonry buildings. For this purpose, nonlinear static analyses are carried out by using three different modeling approaches, based on a continuum model, beam-based and spring-based macro-element models. The performance of each approach was compared based on capacity curves and global damage patterns. Reasonable agreement was found between numerical predictions and experimental observations. Validation of simplified approaches was generally provided with reference to regular structures but, based on the differences in the base shear capacity found here, it appears that structural irregularities are important to be taken into account for acquiring higher accuracy on simplified methods when torsion is present. [ABSTRACT FROM AUTHOR]

• The force-displacement description of collapse in masonry structures is undertaken. • NURBS-based adaptive limit analysis is adopted to compute the collapse mechanism. • Nonlinearities are lumped into tight zones located in correspondence of the fissures. • 3D plastic damaging strips and cohesive-frictional contact-based interfaces are used. • The procedure effectiveness is shown through meaningful structural examples. In this paper, a novel numerical procedure is proposed for the force-displacement description of out-of-plane collapse in masonry structures. The numerical procedure herein proposed represents one first attempt to couple limit analysis-based solutions to displacement-based evolutive analysis strategies. Limit-analysis based solutions are considered trustworthy to investigate collapse mechanisms in masonry structures, even though they cannot be used in displacement-based seismic assessment procedures (e.g. pushover analysis), while displacement-based evolutive analysis strategies (e.g. block-based and anisotropic continuum approaches), which can undertake this last task, are typically computationally demanding and their mechanical characterization is often very challenging. In this research, a genetic algorithm NURBS-based adaptive homogenized upper bound limit analysis is firstly adopted to compute the collapse mechanism that the structure (of any geometrical complexity) experiences for a given loading condition. Then, the 3D geometry of the collapse mechanism is imported in incremental-iterative step-by-step evolutive analysis frameworks to perform pushover analysis. In particular, two numerical modelling approaches are conceived to this aim, both lumping all the mechanical nonlinearities into tight zones located in correspondence of the cracks defined in the collapse mechanism previously computed. The first one uses 3D plastic damaging strips governed by a standard nonlinear continuum constitutive law. The second approach adopts non-standard zero-thickness contact-based interfaces governed by a cohesive-frictional contact behaviour previously developed by the authors for the brick-to-brick mechanical interaction. A number of meaningful structural examples show the effectiveness of the numerical procedure proposed. Pushover curves obtained through different modelling strategies are also critically compared. [ABSTRACT FROM AUTHOR]

Dynamic Soil–Structure Interaction (SSI), involving the coupling of structure, foundation and soil, is a crucial and challenging problem, especially when soil nonlinearity plays an important role. This paper shows the impact of adopting different SSI models on the assessment of seismic fragility functions. The linear substructure approach is initially adopted by implementing two different models, the first of which is one-dimensional and includes, between the foundation node and the ground, 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 (LPM) accounting for frequency dependence of the impedance. In order to explore the sensitivity of fragility functions to the linearity assumption, an additional approach, including soil nonlinearities, is employed. A nonlinear footing macro-element is adopted to model the near-field behaviour by condensing the entire soil-foundation system into a single nonlinear element at the base of the superstructure. Energy dissipation through radiation damping is also accounted for. The superstructure response is simulated in all approaches as a simple nonlinear single-degree-of-freedom (SDOF) system. The comparison between the adopted approaches is evaluated in terms of their effects on the characterisation of fragility functions for unreinforced masonry buildings (URM) on shallow foundations. • In response to induced seismicity in the Netherlands, fragility functions are needed • Dynamic Soil–Structure Interaction (SSI) is a crucial and challenging problem • Three SSI models are implemented and their effects on fragility functions are compared • The collapse fragility curves for ten unreinforced masonry index buildings are provided • The considered inelastic behaviour leads to energy dissipation and smaller displacements [ABSTRACT FROM AUTHOR]

• Finite element modelling (FEM) of perforated unreinforced masonry walls. • Wall geometry and vertical pre-compression has significant effect on the behaviour. • FEA successfully captured the global in-plane behaviour of the tested walls. • Spandrel effect on the global behaviour of the wall is significant. This paper presents numerical modelling of the in-plane shear behaviour of unreinforced masonry (URM) walls with a semicircular arch opening. To do so, two dimensional finite element (FE) modelling of a series of experimentally tested walls was conducted using the simplified micro-modelling approach. The models successfully captured the load-displacement behaviour and, to a large extent, the failure modes of the piers and spandrels observed in the experimentally tested walls. The exception was that the FE modelling did not show pier diagonal shear cracking which was observed in some of the tested walls. The model was then used to perform parametric studies to investigate the effect of geometric variations of the walls as well as the effect of vertical pre-compression stresses on the lateral in-plane capacity of the walls. The results obtained from the FE analyses were compared to the anticipated maximum shear strength and the predicted failure modes according to the New Zealand Society for Earthquake Engineering (NZSEE, 2017). From this study, it is shown that there is a significant effect of the wall geometry and vertical pre-compression load on the failure modes and the lateral load resistance capacity of the walls. In most of the cases investigated, the NZSEE equations for maximum shear strength and failure modes agree well with the FEM results. The arch opening was remodelled to a rectangular opening and it was found that the effective pier height for an equivalent rectangular pier adjacent to a semi-circular arched opening can be taken up to the half height of the arch radius. [ABSTRACT FROM AUTHOR]