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Masonry walls, prevalent in many historical and contemporary structures, often require retrofitting to meet modern safety and performance standards. Motivated by the need for efficient and reliable retrofitting solutions, this research investigates the potential of various types of ferrocement, reinforced with high-strength steel meshes, to enhance the in-plane shear behavior of brick masonry walls. Through rigorous diagonal compression tests on nine masonry wallettes, the study evaluated the performance of ferrocement overlays in terms of overlay configuration (asymmetric or symmetric), cementitious material type (mortar, ECC, or UHPC), the presence or absence of steel mesh, and construction method (shotcrete or prefabricated panels). The results indicated that UHPC and ECC overlays significantly enhanced post-cracking deformation capacity. Compared to the asymmetric retrofit, the symmetric retrofit led to more uniform deformation in the retrofitted wallette, effectively improving the maximum shear by up to 119 %. While UHPC shotcrete was more effective in improving the shear strength, ECC shotcrete led to the highest rupture shear strain and pseudo-ductility for the retrofitted wallette, reaching 0.83 % and 17.2, respectively. Moreover, although steel mesh inclusion in the ferrocement overlay was crucial in enhancing post-peak ductility, its impact on shear strength of the retrofitted wallettes was minimal. The test results also demonstrated that the developed prefabricated UHPC panels emerged as an effective retrofitting solution to simultaneously improve the strength, deformation capacity, and ductility for masonry wallettes. In addition to the experimental investigation, a new strength model, accounting for various key design variables, was developed, offering reliable shear strength predictions for the retrofitted wallettes.

This paper aims to valorize the excavated earth (ExE) generated from the tunnel digging works, to elaborate excavated earth-based plasters for masonry walls. Excavated earth is an admixture of water, gravel, sand, and fine particles. A small amount of gravel (<4% by weight) was removed, and the tunnel-excavated earth is used to elaborate plasters. Cement and slag are used as stabilizers in ExE-based plasters and reinforced with natural hemp fibers. The physical, mechanical, thermal, and hydric properties of ExE-based plasters are investigated. The increase in cement content affects the workability of ExE-based plasters in a fresh state, while the addition of natural hemp fibers has no significant effect on the workability. It has been demonstrated that the mechanical performances (compressive strength, flexural strength, and dynamic modulus) of ExE-based plasters increase with the increase of cement content and decrease with the increase in slag content. The hemp fiber addition (0.8% by weight) shows no considerable effect on the ExE-based plaster's mechanical performance. As for the thermal properties, the increase of cement and slag contents negatively affects the thermal conductivity. The increase in cement content decreases the water absorption of earth-plasters. Except for some tests (shrinkage, main cohesion, and cracking tests), which have not been done in this study, the results of cement-stabilized ExE-based plasters (7% and 9%) are in accordance with the recommendation of the DIN 18947 standard, indicating that the tunnel excavated earth can be used as earth-plasters. [ABSTRACT FROM AUTHOR]

In this research, the effects of different repairing materials and techniques used on damaged Masonry walls under an in-plane lateral loading were investigated. Seven clay brick walls with dimensions of (1200 × 935 × 115) mm were tested. The walls were tested until a visible crack was observed, later repaired, and tested again up to failure. The repairing materials consisted of grid configured strip materials (metal, plastic, flat webbing 'textile' and wild cane 'organic' strips), near surface mounted (NSM) steel re-bars and steel wires in mortar joints. Based on the experimental results, the repairing materials/techniques restored the shear strength by about 48–103% of the original strength. The ductility factor of the repaired walls ranged from 4.5 to 48.3 (flat webbing 'textile' highest). The energy dissipation ratio of the repaired walls ranged from 4.3 to 12.7 (flat webbing 'textile' highest). Prediction equations for shear strength are presented giving reasonable results compared to the experimental results. [ABSTRACT FROM AUTHOR]

Masonry structures primarily rely on their walls as the principal load-bearing components. The walls are brittle materials such as natural stone, sandstone and brick. The walls of masonry structures have lack of the deformation capacity and to resist the tensile stresses caused by earthquake forces, settlement of foundation, and so on. To avoid loss in bearing capacity or to have more strength against lateral loads, during the production or after some precautions can be taken. The aim of this study is to investigate the behavior of strengthened aerated concrete walls by clamps. Six samples were tested under diagonal compression. All tested samples were knitted with mortar advised by the aerated concrete producer. The left five samples were knitted using different orientation of clamps and anchors made out of Ø12 deformed bars and welded plates. According to the experimental test results, it was observed that the interconnection of aerated concrete blocks with different combinations had increased stiffness, energy consumption capacity, and load bearing capacity of the walls. In addition to the brittle behavior of the reference specimen, the strengthened wall specimens have exhibited more ductile behavior.

In this study, the effect of mortar and bond types on the mechanical parameters of masonry walls was investigated experimentally. Accordingly, a total of 108 wall elements were created for four different mortar types (0%, 1%, 2% and 3% steel fiber by weight), three different joint thicknesses (10 mm, 20 mm and 30 mm) and three different bond types (stack bond and stretcher bond (1/2 and 1/3) types). Then, diagonal compression test was carried out for wall elements. As a result of the tests, the failure patterns and the mechanical parameters such as ductility capacity, maximum shear strength, maximum displacement and failure load were obtained for each wall element. The wall element (optimal wall element) showing the best behavior in terms of these mechanical parameters was determined. [ABSTRACT FROM AUTHOR]

Moisture in historic built heritage is one of the main degenerative agents, because it supports or manifests itself through multiple pathologies. Current knowledge allows for the diagnosis and assessment of the problem, but there are deficiencies in the evaluation of corrective systems due to the time it takes for moisture to become significant. In response, this study proposes an experimental methodology that aims to reproduce the accelerated aging of real scale specimens under laboratory conditions. Thereby improving the understanding of the impact of moisture related deterioration on masonry structures. To achive this, eight masonry walls were constructed and subjected to eight cycles of sulfate crystallization. They were saturated with different sulfate concentrations (5% or 10%) and exposed to different drying conditions (outdoor or solar dehydrator) in order to identify the factors favoring sulfate crystallization and the resulting deterioration. The progress of the experiments was monitored using a hygrometer, a thermographic camera and photogrammetry. The results indicate that it is possible to induce efflorescence in real scale specimens. Temperature and moisture monitoring helped identify the solar dehydrator as a more effective drying treatment. While digital photogrammetry was considered inefficient for quantifying volumetric damage, since this technique can present errors greater than 2%, a value exceeding the observed wear. Reason why the weight of material detached at the end of the experiment was recorded and a positive correlation between the increase in sulfate concentration and the use of the dehydrator was observed. Finally, pertinent considerations are made to improve the experimental conditions. [ABSTRACT FROM AUTHOR]

This paper is the continuation of a previous study, which highlighted some inconsistencies in the RILEM guidelines for the interpretation of the diagonal compression test. Although improved compared to the ASTM guidelines, in fact, the RILEM guidelines underestimate the state of hydrostatic stress induced by the diagonal compression test at the center of the wallette. The new interpretation of the diagonal compression test proposed in this article shows that the RILEM guidelines actually underestimate both the hydrostatic and the deviatoric stress states at the center of the wallette. The new formulation complies with the linear elastic theory and allows us to use the diagonal compression test to identify the three elastic coefficients of masonry. In particular, it allows the identification of the Poisson ratio, which instead takes on a conventional value in the RILEM and ASTM guidelines. The difference of one order of magnitude between the conventional and proposed Poisson's ratio is in agreement with the experimental results on another brittle material, namely concrete. Finally, the new proposal fills the gap between the results provided by the two tests usually performed to identify the shear behavior of masonry: the diagonal compression test and the shear-compression test. [ABSTRACT FROM AUTHOR]

Among all the active confinement techniques, the use of pre-tensioned stainless steel straps has recently gained much attention. The flexibility of the stainless steel straps allows us to bend and pass them through the thickness of the masonry, thus creating a three-dimensional strengthening system between the two opposite facings. The use of the same perforation for the passage of several straps closed in a loop generates a continuous strengthening system that prevents parts of the structure from falling and injuring the occupants during seismic events. However, the perforations can nullify the in-plane strengthening, as they act as cylindrical hinges and make the reinforcement system labile for certain strap arrangements. Diagonal compression tests on square masonry panels performed in the present study show that the straps improve neither strength nor ductility when running along the mortar head and bed joints, arranged in square meshes. Conversely, they improve both strength and ductility when the straps make angles of ±45° with the mortar joints. Furthermore, the experimental results show that the straps exert an anisotropic effect that decreases the apparent in-plane Poisson ratio. They also provide new insights into the diagonal compression test and allow formulating a new proposal for the pseudo-ductility factor. [ABSTRACT FROM AUTHOR]

Masonry infill walls are commonly used as partitions and exterior walls in many countries. Generally, the masonry wall is executed without any gap from the frame, which leads to the interaction between the structural frame and the infill wall. Interaction between the structural frame and the masonry infill wall can damage the frame and the infill wall. Therefore, it is necessary to find a solution to improve the performance of masonry infill walls in the structural frame. Isolation of the masonry infill wall from the surrounding frame by polymeric material is the idea of this paper to decrease the damage to the structure and masonry infill. In this essay, Finite element models of steel infill frame and isolated infill frame subjected to In-Plane cyclic loading are developed in ABAQUS. For this purpose, three one-bay, one-story masonry-infilled steel frames with different frame ratios of height to the length (H/B) isolated by different polymeric materials with various thicknesses were investigated. Isolation of masonry infill can reduce the base reaction about 25%. In the Isolated Infill wall, the drift’s amount increases about two times compared with the unseparated infill wall. Therefore, it damages the masonry infills up to moderate drifts, while full interaction is still in place drifts are large. Also, infill walls isolated by a softer polymer, have better performance. In brief, isolation of infill wall using polymeric materials improves the behavior of the infill and frame.

The use of FRP materials as external reinforcement of masonry structures has been recognized as an effective and minimally invasive method ofwall strengthening. The available literature and research reports confirmthe positive effect of the strip-like arrangement of composites with a horizontal, diagonal and – as shown in the paper – vertical configuration. The problem here is the proper estimation of the benefits of such FRP reinforcement, namely determining the real increase in shear strength. The paper described selected calculation procedures that can be found in the available literature (proprietary solutions), as well as in the published guidelines for the design of masonry walls strengthening using FRP materials. The results of experimental tests of sheared masonry walls made of AAC blocks and strengthened using vertical strips of carbon and glass fibres are briefly presented. Finally, based on the presented formulae, the values of the theoretical shear force resulted from the FRP contribution were calculated and detailed discussed. The comparison of the experimental and theoretical shear forces showed that only one of the presented calculation methods gave a high agreement of the results for both carbon and glass sheets. In addition, it was noticed that in two cases the effects of strengthening – depending on the material used – drastically differed, which was not observed in the research.

In the territory of Herzegovina there is a large number of masonry buildings, the age of which exceeds 50 years. These are mostly smaller buildings, with one to two floors, while the load-bearing walls are mainly made of cut stone in lime mortar. Larger buildings with load-bearing walls made of bricks and concrete blocks in cement-lime mortar appeared a little later. The floor structures mainly consist of timber oak beams, supported by load-bearing walls, with boarding on the upper side and plaster, on reed netting, on the lower side. Such structures are exceptionally sensitive to seismic action, and almost certainly could not withstand the design seismic load without significant damage and collapse. A nonlinear static analysis of the structure of one such building was performed in this paper. A check of the existing condition was performed in the first analysis, and a check of the partially strengthened structure in the second. It is evident from the analysis that such strengthening significantly improves the bearing capacity, while the increase in deformability (ductility) is significantly smaller due to the very high stiffness of such structures.

This study presents an innovative approach to enhance the flexural capacity of cement-clay interlocking (CCI) brick walls using ferrocement jackets with an expanded wire mesh. The investigation involved 15 CCI brick walls subjected to flexural load testing, exploring various mesh sizes and anchor configurations on single and dual sides. The results revealed that while the primary failure mode involved dry joint opening and subsequent ferrocement debonding in the strengthened walls, effective anchorage mechanisms delayed dry joint opening until debonding occurred. The reinforced walls exhibited improved peak load capacity, notably in dual-sided reinforcement cases. With plastering on both sides and supplemented with anchors, an improvement of up to 221% in flexural capacity was obtained. The study emphasizes the influence of wire mesh size on anchorage effectiveness and its correlation with debonding susceptibility. Additionally, the moment-curvature analysis demonstrated resilient, ductile responses in load-bearing characteristics, with occasional abrupt declines due to ferrocement jacket debonding. Unlike control walls, the strengthened walls exhibited strains exceeding yield thresholds, indicating enhanced structural performance.

During the earthquake, masonry walls are subjected to both in‐plane and out‐of‐plane loading. The walls are interconnected in the masonry buildings at the corners and other locations. The cross walls connected to the main walls considerably affect the behavior of the masonry walls, which has not been paid enough attention to in previous studies. Therefore, the present study focuses on the effect of cross walls on the interaction curves of unreinforced masonry walls. The interaction curves have been obtained by applying the out‐of‐plane pressure to the walls, followed by the uniform in‐plane displacement at its top. Both in‐plane and out‐of‐plane loads are applied unidirectionally on the walls. The walls have been analyzed in the finite element software Abaqus using the simplified micro‐modeling approach. Masonry walls with cross‐sections of rectangular shape, C shape, H shape, and T shape have been considered herein. Further, the effect of varying aspect ratios and pre‐compressions on the interaction curves of the walls has been assessed. An empirical equation has been proposed to obtain the interaction curves of the masonry walls of different shapes, which depends on the aspect ratio and pre‐compression applied to the walls. It has been observed that the in‐plane strengths of the walls are sensitive to the pressure applied in the out‐of‐plane direction on them. The in‐plane strength of the walls reduces rapidly after exceeding the critical out‐of‐plane pressure. Further, it has been found that the shapes of the walls also significantly impact the interaction curves of the masonry walls. The cross walls connected to the main wall noticeably affect the walls' strength and stiffness as well. [ABSTRACT FROM AUTHOR]

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This study aimed to investigate the feasibility and effectiveness of spray-on polyurethane coating as a seismic strengthening method for rural masonry buildings. Three masonry wall specimens were tested under cyclic lateral loading, including a control specimen, a single-side strengthened specimen, and a double-side strengthened specimen. Digital image correlation (DIC) techniques were used to evaluate full-field strain, crack width, and failure progression in a non-contact manner. The seismic performances were compared in terms of failure mode, hysteretic behavior, skeleton curve, deformation performance, energy dissipation capacity, and stiffness degradation. Results indicated that a spray-on polyurethane coating effectively delayed the onset and progression of cracks, postponing the peak load and slowing strength and stiffness degradation. Compared to the unstrengthened specimen, the bearing capacity, ultimate displacement, and cumulative energy dissipation of the single-side strengthened specimen increased by 20%, 60%, and 514%, respectively. Compared to the single-side strengthened specimen, the double-side strengthened specimen BW-D exhibited improved integrity, deformation capacity, and energy dissipation capacity. Its ultimate displacement and cumulative energy dissipation increased by 28% and 10%, respectively. [ABSTRACT FROM AUTHOR]

Identification of crack location and severity is a vital step in assessment of deteriorated structures. The current research addresses the sensitivity of using modal displacement, modal curvature, and modal strain energy functions as Damage Indices (D.I.s) for crack detection. Comparison of these indicators at cracked and undamaged conditions was performed. Firstly, Damage Index (D.I.) method was utilized on synthetic data obtained with the aid of finite element modelling on different flexural elements. The technique was again used to identify cracks for physical scaled-down masonry walls. Three clayey bricks walls with different thicknesses and crack configurations were prepared for this purpose. Each wall was tested in its virgin and damaged states. Formal modal analysis was conducted. It was concluded that all the used D.I.s were accepted as damage indicators. It can also be stated that the relative severity between cracks can be obtained. Numerically, D.I. method was found effective in cases of multiple or inclined cracks. Generally, the identification based on curvature functions, were better than displacement functions for the same number of monitoring points and crack severity. Curvature can’t, however, be easily obtained for sophisticated structures with limited data. Moreover, the detection process became easier as the crack dimensions increased.

Masonry infill walls are commonly used as partitions and exterior walls in many countries. Generally, the masonry wall is executed without any gap from the frame, which leads to the interaction between the structural frame and the infill wall. Interaction between the structural frame and the masonry infill wall can damage the frame and the infill wall. Therefore, it is necessary to find a solution to improve the performance of masonry infill walls in the structural frame. Isolation of the masonry infill wall from the surrounding frame by polymeric material is the idea of this paper to decrease the damage to the structure and masonry infill. In this essay, Finite element models of steel infill frame and isolated infill frame subjected to In-Plane cyclic loading are developed in ABAQUS. For this purpose, three one-bay, one-story masonry-infilled steel frames with different frame ratios of height to the length (H/B) isolated by different polymeric materials with various thicknesses were investigated. Isolation of masonry infill can reduce the base reaction about 25%. In the Isolated Infill wall, the drift's amount increases about two times compared with the unseparated infill wall. Therefore, it damages the masonry infills up to moderate drifts, while full interaction is still in place drifts are large. Also, infill walls isolated by a softer polymer, have better performance. In brief, isolation of infill wall using polymeric materials improves the behavior of the infill and frame. [ABSTRACT FROM AUTHOR]

In the territory of Herzegovina there is a large number of masonry buildings, the age of which exceeds 50 years. These are mostly smaller buildings, with one to two floors, while the load-bearing walls are mainly made of cut stone in lime mortar. Larger buildings with load-bearing walls made of bricks and concrete blocks in cement-lime mortar appeared a little later. The floor structures mainly consist of timber oak beams, supported by loadbearing walls, with boarding on the upper side and plaster, on reed netting, on the lower side. Such structures are exceptionally sensitive to seismic action, and almost certainly could not withstand the design seismic load without significant damage and collapse. A nonlinear static analysis of the structure of one such building was performed in this paper. A check of the existing condition was performed in the first analysis, and a check of the partially strengthened structure in the second. It is evident from the analysis that such strengthening significantly improves the bearing capacity, while the increase in deformability (ductility) is significantly smaller due to the very high stiffness of such structures. [ABSTRACT FROM AUTHOR]

Fabric-reinforced cementitious matrix (FRCM) composites, also known as textile-reinforced mortars (TRMs), represent a new advancement in structural repair and reinforcement technology. Aiming to improve the energy efficiency and seismic performance of existing buildings, this research focused on the development of an FRCM system in combination with phase change materials (PCMs) and extruded polystyrene sheets (XPS) to achieve adequate mechanical and thermal properties for reinforced concrete (RC) and masonry structures. Accordingly, the in-plane behaviour of five FRCM-strengthened RC frames with hollow-brick wall infill was tested under cyclic loading to investigate the improvement in earthquake resistance. The system was comprehensively evaluated by calculating hysteresis curves; comparing the lateral stiffness, ductility, and energy dissipation capacity; measuring the deformations of the specimens; and analysing the failure modes mechanically. Finally, it was proved that this novel integrated approach could significantly enhance the mechanical and seismic performance of masonry-infilled RC frames. [ABSTRACT FROM AUTHOR]

A render is the first protective layer of exterior walls against the outdoor climate, which, due to its constitution, aims to gradually slow down the liquid moisture penetration to prevent it from reaching the wall inner layers. Due to the future expected changes in the outdoor climate, today's exterior mortar might not be adequately designed to protect these walls. This paper aims to analyse the influence of mortars on the hygrothermal performance of solid brick walls under current and future climates. The study includes four types of assemblies and three types of mortars, and it was carried out for Lisbon and three other climates by using a computational simulation tool. Finally, the moisture gains and respective reach due to the future wind-driven rain (WDR) spells were assessed by means of using future weather files for Lisbon's climate. It was shown that the solid brick layer is influenced differently depending on the characteristics of the mortar layers and outdoor conditions. In terms of WDR spells, aside from the precipitation and the spell period, the distribution of the WDR events within the spell also conditions the dryness of the assembly. The depth that the outdoor moisture was able to reach varies between 94 and 200 mm. [ABSTRACT FROM AUTHOR]

The use of FRP materials as external reinforcement of masonry structures has been recognized as an effective and minimally invasive method ofwall strengthening. The available literature and research reports confirmthe positive effect of the strip-like arrangement of composites with a horizontal, diagonal and - as shown in the paper - vertical configuration. The problem here is the proper estimation of the benefits of such FRP reinforcement, namely determining the real increase in shear strength. The paper described selected calculation procedures that can be found in the available literature (proprietary solutions), as well as in the published guidelines for the design of masonry walls strengthening using FRP materials. The results of experimental tests of sheared masonry walls made of AAC blocks and strengthened using vertical strips of carbon and glass fibres are briefly presented. Finally, based on the presented formulae, the values of the theoretical shear force resulted from the FRP contribution were calculated and detailed discussed. The comparison of the experimental and theoretical shear forces showed that only one of the presented calculation methods gave a high agreement of the results for both carbon and glass sheets. In addition, it was noticed that in two cases the effects of strengthening - depending on the material used - drastically differed, which was not observed in the research. [ABSTRACT FROM AUTHOR]

In the study, the effect of mortar type on the mechanical parameters of masonry walls was investigated. Mortar containing micro steel fiber were used as mortar type. Within the scope of the experimental study, firstly some physical and mechanical experiments were carried out for the sand, brick and mortar. Then, a total of 12 walls with dimensions of 610 × 90 × 610 mm were created for four different mortar types. The walls were subjected to the diagonal compression test. As a result of the tests, the failure patterns and the mechanical parameters such as ductility capacity, maximum shear strength, maximum displacement and failure load were obtained for walls. It was determined that the optimal wall that showed the best behavior in terms of these mechanical parameters was the wall formed with a mortar containing 2% micro steel fiber. According to the experimental results, it has been determined that the mechanical parameters of masonry walls can be improved by using micro steel fiber in the joint mortar. The optimum fiber ratio for this study was determined as 2%. For this reason, it was concluded that the fiber ratio used in the mortar should be at a certain level. Within the scope of the finite element study, finite element model was created for the optimal wall by using macro modelling technique. The Drucker Prager criterion was used for the nonlinear behavior of the wall. The effectiveness of the solutions was assessed by comparing with the experimental results. [ABSTRACT FROM AUTHOR]

Identification of crack location and severity is a vital step in assessment of deteriorated structures. The current research addresses the sensitivity of using modal displacement, modal curvature, and modal strain energy functions as Damage Indices (D.I.s) for crack detection. Comparison of these indicators at cracked and undamaged conditions was performed. Firstly, Damage Index (D.I.) method was utilized on synthetic data obtained with the aid of finite element modelling on different flexural elements. The technique was again used to identify cracks for physical scaled-down masonry walls. Three clayey bricks walls with different thicknesses and crack configurations were prepared for this purpose. Each wall was tested in its virgin and damaged states. Formal modal analysis was conducted. It was concluded that all the used D.I.s were accepted as damage indicators. It can also be stated that the relative severity between cracks can be obtained. Numerically, D.I. method was found effective in cases of multiple or inclined cracks. Generally, the identification based on curvature functions, were better than displacement functions for the same number of monitoring points and crack severity. Curvature can't, however, be easily obtained for sophisticated structures with limited data. Moreover, the detection process became easier as the crack dimensions increased. [ABSTRACT FROM AUTHOR]

Given that a significant fraction of buildings and architectural heritage in Europe's historical centers are masonry structures, the selection of proper diagnosis, technological surveys, non-destructive testing, and interpretations of crack and decay patterns is paramount for a risk assessment of possible damage. Identifying the possible crack patterns, discontinuities, and associated brittle failure mechanisms within unreinforced masonry under seismic and gravity actions allows for reliable retrofitting interventions. Traditional and modern materials and strengthening techniques create a wide range of compatible, removable, and sustainable conservation strategies. Steel/timber tie-rods are mainly used to support the horizontal thrust of arches, vaults, and roofs and are particularly suitable for better connecting structural elements, e.g., masonry walls and floors. Composite reinforcing systems using carbon, glass fibers, and thin mortar layers can improve tensile resistance, ultimate strength, and displacement capacity to avoid brittle shear failures. This study overviews masonry structural diagnostics and compares traditional and advanced strengthening techniques of masonry walls, arches, vaults, and columns. Several research results in automatic surface crack detection for unreinforced masonry (URM) walls are presented considering crack detection based on machine learning and deep learning algorithms. In addition, the kinematic and static principles of Limit Analysis within the rigid no-tension model framework are presented. The manuscript sets a practical perspective, providing an inclusive list of papers describing the essential latest research in this field; thus, this paper is useful for researchers and practitioners in masonry structures. [ABSTRACT FROM AUTHOR]

Many masonry structures are constructed with cement clay interlocking brick (CCIB) due to its added benefits. Recent research has demonstrated the vulnerability of brick masonry walls against seismic loading. Various strengthening materials and techniques are extensively used to improve the structural behavior of brick walls. Carbon fiber-reinforced polymer (CFRP) composites are the most popular strengthening material due to their advantages of easy application, lightweight qualities, and superior tensile strength. The current research work aimed to explore the cost-effective solutions and feasibility of CFRP composite-based strengthening techniques to improve the load-bearing capacity of CCIB walls. Various configurations and combinations of strengthening materials were investigated to customize the cost of repair and strengthening. The experimental results indicated that CFRP composites in combination with cement-sand (CS) mortar are an efficient strengthening material to enhance the strength and ultimate deflection of CCIB walls. The ultimate load-bearing capacity and axial deformation of the strengthened CCIB wall (using two layers of CFRP strips and CS mortar of 10 mm thickness) remained 171% and 190% larger than the unstrengthened CCIB wall. The conclusions of this study are expected to enhance the seismic performance of masonry buildings in developing countries. It should be noted that due to the reduced number of tested specimens, the results to be assumed as general considerations need a wider experimental campaign and a large numbers of tests for each strengthening typology. [ABSTRACT FROM AUTHOR]

The low cost of cement-clay interlocking (CCI) bricks is an attractive feature, resulting in a wide utilization of CCI bricks in the construction of masonry walls. Despite this, an experimental database on the performance of CCI brick walls is scarce. This study tested ten large masonry walls constructed with CCI bricks in a running bond pattern. Two types of CCI bricks were used to assess the effect of chemical position on the diagonal compressive capacity of walls. Further, different grouts and steel bars were used within the openings in CCI bricks. A combination of grout and steel bars resulted in the optimal improvement of the diagonal compressive strength, whereas up to 110% higher improvement in the diagonal compressive strength was achieved by doubling the compressive strength of grout. Interestingly, the type of bricks did not influence the improvement in the diagonal compressive capacity of CCI brick masonry walls. A regression-based equation was proposed to predict the diagonal compressive capacity of CCI brick walls by including the yield strength of steel bars, the compressive strength of grout, and the diagonal compressive strength of ungrouted walls as explanatory variables. The predicted capacities of CCI brick walls were found to be in close agreement with experimental results.

Among all the active confinement techniques, the use of pre-tensioned stainless steel straps has recently gained much attention. The flexibility of the stainless steel straps allows us to bend and pass them through the thickness of the masonry, thus creating a three-dimensional strengthening system between the two opposite facings. The use of the same perforation for the passage of several straps closed in a loop generates a continuous strengthening system that prevents parts of the structure from falling and injuring the occupants during seismic events. However, the perforations can nullify the in-plane strengthening, as they act as cylindrical hinges and make the reinforcement system labile for certain strap arrangements. Diagonal compression tests on square masonry panels performed in the present study show that the straps improve neither strength nor ductility when running along the mortar head and bed joints, arranged in square meshes. Conversely, they improve both strength and ductility when the straps make angles of ±45° with the mortar joints. Furthermore, the experimental results show that the straps exert an anisotropic effect that decreases the apparent in-plane Poisson ratio. They also provide new insights into the diagonal compression test and allow formulating a new proposal for the pseudo-ductility factor.

This paper is the continuation of a previous study, which highlighted some inconsistencies in the RILEM guidelines for the interpretation of the diagonal compression test. Although improved compared to the ASTM guidelines, in fact, the RILEM guidelines underestimate the state of hydrostatic stress induced by the diagonal compression test at the center of the wallette. The new interpretation of the diagonal compression test proposed in this article shows that the RILEM guidelines actually underestimate both the hydrostatic and the deviatoric stress states at the center of the wallette. The new formulation complies with the linear elastic theory and allows us to use the diagonal compression test to identify the three elastic coefficients of masonry. In particular, it allows the identification of the Poisson ratio, which instead takes on a conventional value in the RILEM and ASTM guidelines. The difference of one order of magnitude between the conventional and proposed Poisson’s ratio is in agreement with the experimental results on another brittle material, namely concrete. Finally, the new proposal fills the gap between the results provided by the two tests usually performed to identify the shear behavior of masonry: the diagonal compression test and the shear-compression test.

A new interface element constitutive model is proposed in this study for analyzing masonry using the simplified micromodeling (SMM) approach, in which mortar and two unit-mortar interfaces are lumped into a zero-thickness joint (modeled using an interface element) between expanded masonry units. The new model is capable of simulating tension cracking, shear slipping, and compression failure, and is defined by a convex composite failure surface consisting of a tension-shear and a compression cap failure criterion. It removes the singularity in the tension-shear region but not in the compression-shear region. In addition, the proposed model is based on the hypothesis of strain hardening. The robustness and computational cost of the proposed model were compared with different constitutive models (which are based on three, two, and one failure criteria) that have been widely used in the literature to describe masonry behavior through a series of one-element tests and through the comparison of finite-element (FE) response simulation of an unreinforced masonry shear wall. The FE response results indicate that the proposed constitutive model is more efficient than and at least as accurate as the other constitutive models for analyzing masonry using the SMM approach.

Through numerical simulation, the blast-resistant performance of spray polyurea elastomer (SPUA) retrofitted concrete masonry unit (CMU) masonry infill walls under far-range blast loading was studied. From an engineering perspective, the effects of boundary conditions and thickness of a SPUA layer on enhancing the blast resistance of masonry infill walls are discussed, and the blast resistance of SPUA-retrofitted and grouted CMU masonry infill walls are compared. It is concluded that the boundary constraint conditions and the anchorage length of SPUA layer have limited improvement on the blast-resistant performance of the wall; the thickness of SPUA layer can significantly improve the blast-resistant performance of the wall as the blast loading increases. In addition, SPUA retrofitting shows relatively better performance to reinforce masonry infill walls. [ABSTRACT FROM AUTHOR]

As a common enclosure structure, masonry walls are widely used in various types of buildings. However, due to the weak out-of-plane resistance of masonry walls and the generally brittle properties of the materials used for blocks, they are highly susceptible to collapse under blast loads and produce high-speed splash fragments, which seriously threatens the safety of personnel and equipment inside buildings. In this paper, based on the existing tests, a refined numerical simulation model was established to carry out numerical studies of clay tile walls and grouted CMU masonry infill walls under far-range blast loads, and the applicability of the finite element model and parameters were verified. Further, the effects of wall boundary configuration, constraints and dimensions on the dynamic response of the walls were carried out. The results show that: the load distribution on the wall is relatively uniform under the far-range explosion and can be considered as uniform load; the blast-resistant performance of the wall can be enhanced by increasing the grouting rate and the uniformity of grout hole distribution; the boundary configuration of the wall has little effect on the blast resistance, while the boundary constraints and the length and width are the main factors affecting the blast resistance of the wall. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study of the shear behavior of masonry walls made of aero autoclaved concrete (AAC) blocks strengthened by externally bonded fiber-reinforced polymer (FRP) composites. Fifteen small wall specimens were constructed and tested in a diagonal compression scheme. Two types of composite materials—carbon- and glass-reinforced polymers—were arranged in two configurations of vertical strips, adopted to the location of the unfilled head joints. The effect of the strengthening location and strengthening materials on changes in the strength and deformability parameters are discussed and the failure process of unstrengthened walls is also presented. The placement of the composite on unfilled head joints proved to be a better solution. Carbon-fiber-reinforced polymer (CFRP) strips provided a threefold increase in stiffness, a 48% increase in load-bearing capacity and a high level of ductility in the post-cracking phase. Glass-fiber-reinforced polymer (GFRP) strips offered a 56% increase in load-bearing capacity but did not change the stiffness of the masonry and provided relatively little ductility. Placing the composite between unfilled joints was only reasonable for CFRP composites, providing a 35% increase in load-bearing capacity but with negligible ductility of the masonry. [ABSTRACT FROM AUTHOR]

The susceptibility of masonry walls to out-of-plane failure under seismic loading presents a significant engineering concern. In adherence to contemporary limit state design philosophy and as mandated by performance-based design guidelines, it is crucial to accurately estimate statistics parameters such as the mean and variance of out-of-plane resistance. To achieve this, two deterministic models are often considered within the Monte Carlo simulation framework: design-code models, known for their computational efficiency but potential for significant model error, and mechanics-based finite element models, noted for their accuracy but computational intensity. Relying solely on either model for statistics estimation presents challenges due to their respective inherent limitations. This study introduces an improved strategy that synergizes the strengths of both models, resulting in enhanced statistics estimators for the out-of-plane resistance of masonry walls. The proposed methodology involves the use of the control variate method by integrating numerous design-code model evaluations to boost computational efficiency while incorporating a limited number of finite element model evaluations to ensure accuracy. The constructions of the proposed estimators follow rigorous optimization procedures to minimize associated errors and variances. Theoretical derivations are provided for essential elements in the estimator constructions, such as model evaluation numbers for finite element and design-code models and control variate coefficients. Moreover, the accuracy of the proposed estimators is compared with that of the crude Monte Carlo estimator. A key benefit of the proposed estimators is their unbiased nature, and their accuracy is not compromised by the discrepancies between the finite element model and the design-code model. To demonstrate the practicality of these estimators, two case studies are illustrated: one focusing on unreinforced masonry walls and the other on reinforced masonry walls. The results indicate that design-code model-based estimators exhibit large bias, and compared to the estimators that solely rely on the finite element model, the proposed estimators achieve higher accuracy given the same computational budget. • An improved strategy is proposed for estimating statistics of the OOP resistance of masonry walls. • The proposed methodology leverages a limited number of expensive finite element models and a large number of efficient design-code models. • The proposed mean and variance estimators are unbiased. • Two case studies are presented to show the performance of the proposed estimators. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the feasibility and effectiveness of spray-on polyurethane coating as a seismic strengthening method for rural masonry buildings. Three masonry wall specimens were tested under cyclic lateral loading, including a control specimen, a single-side strengthened specimen, and a double-side strengthened specimen. Digital image correlation (DIC) techniques were used to evaluate full-field strain, crack width, and failure progression in a non-contact manner. The seismic performances were compared in terms of failure mode, hysteretic behavior, skeleton curve, deformation performance, energy dissipation capacity, and stiffness degradation. Results indicated that a spray-on polyurethane coating effectively delayed the onset and progression of cracks, postponing the peak load and slowing strength and stiffness degradation. Compared to the unstrengthened specimen, the bearing capacity, ultimate displacement, and cumulative energy dissipation of the single-side strengthened specimen increased by 20%, 60%, and 514%, respectively. Compared to the single-side strengthened specimen, the double-side strengthened specimen BW-D exhibited improved integrity, deformation capacity, and energy dissipation capacity. Its ultimate displacement and cumulative energy dissipation increased by 28% and 10%, respectively.

Unreinforced masonry buildings are prone to catastrophic damage when subjected to debris-flow impact. Engineered cementitious composite (ECC) layers were utilized to strengthen unreinforced masonry walls belonging to a 1/2 scaled timber-masonry building to mitigate the risk of collapse, and rolling steel balls of various masses were used to impact the strengthened walls to investigate the effects of the ECC layer strengthening. The typical characteristics of ECC, i.e., multiple cracking and high damage tolerance, were clearly exhibited during impacting, which helped to transfer the failure mode of the masonry walls from brittle to a much more ductile one. This article introduces strain response, displacement response, acceleration response, and dynamic property of the strengthened walls under impact. The test results demonstrated that ECC layer strengthening can significantly enhance impact resistance, including stiffness, energy dissipation, etc. For simplified assessment, the residual displacement ratio is recommended as the indicator to characterize the damage level of masonry walls strengthened with the ECC layers. [ABSTRACT FROM AUTHOR]

In order to correctly define the pathology of multiple-leaf stonemasonry walls and determine the appropriate interventions for its conservation and preservation, comprehensive studies on its building materials should be carried out since the overall behaviour of masonry structures is highly dependent on the characterization of its construction materials. Consequently, an interdisciplinary procedure for construction material characterization used in multiple-leaf stone-masonry walls in Egypt has been implemented to enrich documentation, conservation and restoration issues of this type of wall. The research methodology integrates experimental data obtained through on-site sampling, conducted tests and analyses, historical information, and field survey observations. The fundamental physical and mechanical properties of the masonry elements were examined by incorporating stone blocks, mortars and core-infill materials. The mineralogical composition and interlocking textures of the collected samples were investigated utilizing a large range of complementary investigation and analysis techniques, including polarizing microscopy, X-ray diffraction (XRD), thermal analysis (TG/DTA), and environmental scanning electron microscope (ESEM) attached to an EDX unit. Through the results thus obtained, a complete characterization of the mineralogical composition; physical–mechanical, chemical, and thermal properties; and the interlocking textures of the construction materials of both the outer and inner-core layers was performed. The outer leaves of the majority of the multiple-leaf stone-masonry walls in medieval architectural heritage were mainly built of well-dressed limestone blocks with nearly uniform dimensions, while the inner-core layer was usually built of stone-rubble infill with bending lime-based mortar. The uniaxial compressive strengths of core infill (corresponding to the inner core layer) and lime-based mortar of the embedded joints are shown to be 85 and 92.5% lower than the limestone units of the outer layer, respectively. Moreover, experimental observations indicate that the inner core layer exhibits the highest porosity values; consequently, deteriorated, loose and cohesionless core infill could greatly affect the durability and thermal resistivity of this kind of wall. The results provide scientific support for investigating the overall structural behaviour of this type of walls and for decision-making in future conservation and restoration strategies.

While openings are an essential requirement in buildings as a source of access, fresh air and sunlight, these openings cause a reduction in the lateral stiffness and torsional resistance of masonry wall units. A detailed numerical investigation was carried out to explore the impact of the opening percentage on the in-plane stiffness and lateral strength of unconfined and confined masonry wall panels prepared using calcium silicate bricks, for sustainable masonry structures. A commercially available FEM package (ANSYS) was used to carry out comparative analysis of ten wall panels, five of each type (confined and unconfined masonry walls) with concentrically located openings of varying sizes (0% to 16.5%). A simplified micro-modeling technique following the Newton Raphson Algorithm was adopted. Results revealed that the confined masonry approach unveiled a more reliable anti-seismic response along with improved in-plane strength in the case of confined masonry walls. The failure type shifted from pure flexural to more of a blend of shear and flexure after the opening percentage increased to 10.09% in unconfined masonry walls, which was not the case where confinement was provided. Based on the outcomes, it is strongly recommended to adopt confined masonry in highly seismic-prone areas to avoid catastrophic damage caused by earthquakes. [ABSTRACT FROM AUTHOR]

Many unreinforced masonry structures were vulnerable in the past earthquakes and required retrofitting. The vulnerability of masonry structures could solve by providing numerous retrofitting approaches. However, the lack of appropriate methods, which could provide a solution for historical masonry structures with lesser effects on their façade, is demanding. In this study, two one-third scale masonry wall specimens made by clay bricks were tested under constant vertical and cyclic lateral loading. The specimens consist of an unreinforced wall and a wall retrofitted by GFRP strips. This study investigates the seismic behavior of unreinforced masonry walls before and after using GFRP strips on their bedjoints. To this purpose, various patterns of using GFRP strips have been studied by simplified micro-modeling. The results indicate that the proposed retrofitting technique could improve the lateral strength and stiffness of the unreinforced masonry wall with a considerable increase in the absorbed and dissipated energy and ductility content that changes the wall's brittle failure to the ductile one. The proposed method could apply to the modern historical structures in which cement mortar has been used as an adhesive between the masonry layers. [ABSTRACT FROM AUTHOR]

The qualitative aspect of visual inspection of damaged structures can be largely benefited by incorporating quantitative metrics. Moreover, automating this process requires the development of effective computational tools capable of making reliable assessments, appropriately calibrated to the mechanical and structural characteristics of the systems under analysis. In this paper, two damage indices are determined based on the topology of crack patterns. The results of an experimental campaign involving six plastered stone masonry walls are used to show that, for walls constructed with uncut limestone blocks and pebbles, these damage indices are correlated with strength degradation. To this end, topological data analysis is employed to estimate persistent diagrams and minimum spanning trees of crack patterns extracted from digital images using convolutional neural networks and signal processing techniques. The results show that the topological complexity of crack patterns is a strong indicator of the damage level in structures. • Damage indices are developed based on the topological features of crack patterns. • Experimental data from masonry walls under lateral cyclic loading are analyzed. • Deep neural networks and signal processing are used for analyzing crack patterns. • Persistent homology is related to the strength degradation of stone masonry walls. [ABSTRACT FROM AUTHOR]

A render is the first protective layer of exterior walls against the outdoor climate, which, due to its constitution, aims to gradually slow down the liquid moisture penetration to prevent it from reaching the wall inner layers. Due to the future expected changes in the outdoor climate, today’s exterior mortar might not be adequately designed to protect these walls. This paper aims to analyse the influence of mortars on the hygrothermal performance of solid brick walls under current and future climates. The study includes four types of assemblies and three types of mortars, and it was carried out for Lisbon and three other climates by using a computational simulation tool. Finally, the moisture gains and respective reach due to the future wind-driven rain (WDR) spells were assessed by means of using future weather files for Lisbon’s climate. It was shown that the solid brick layer is influenced differently depending on the characteristics of the mortar layers and outdoor conditions. In terms of WDR spells, aside from the precipitation and the spell period, the distribution of the WDR events within the spell also conditions the dryness of the assembly. The depth that the outdoor moisture was able to reach varies between 94 and 200 mm.

Many masonry structures are constructed with cement clay interlocking brick (CCIB) due to its added benefits. Recent research has demonstrated the vulnerability of brick masonry walls against seismic loading. Various strengthening materials and techniques are extensively used to improve the structural behavior of brick walls. Carbon fiber-reinforced polymer (CFRP) composites are the most popular strengthening material due to their advantages of easy application, lightweight qualities, and superior tensile strength. The current research work aimed to explore the cost-effective solutions and feasibility of CFRP composite-based strengthening techniques to improve the load-bearing capacity of CCIB walls. Various configurations and combinations of strengthening materials were investigated to customize the cost of repair and strengthening. The experimental results indicated that CFRP composites in combination with cement-sand (CS) mortar are an efficient strengthening material to enhance the strength and ultimate deflection of CCIB walls. The ultimate load-bearing capacity and axial deformation of the strengthened CCIB wall (using two layers of CFRP strips and CS mortar of 10 mm thickness) remained 171% and 190% larger than the unstrengthened CCIB wall. The conclusions of this study are expected to enhance the seismic performance of masonry buildings in developing countries. It should be noted that due to the reduced number of tested specimens, the results to be assumed as general considerations need a wider experimental campaign and a large numbers of tests for each strengthening typology.