Brick Masonry Panels Research Articles

Two-heads brick masonry walls strengthened by basalt and glass chopped fiber mortar: Effect of bed joints and coating reinforcements

It is urgent finding strengthening systems for masonry structures located in seismic areas. This paper studies the effect of chopped fibers embedded in a cementitious mortar to be used as a strengthening system for two-heads brick masonry panels subjected to diagonal compressive forces. The strengthening system provides the use of two types of chopped fibers dispersed in the mortar matrix, i.e. a glass fiber reinforced mortar (GFRM) and a basalt fiber reinforced mortar (BFRM). The retrofitting composite material is disposed in three different ways: (i) the reinforced mortar is placed within the mortar joints of masonry panel; (ii) the reinforced mortar is disposed on both external surfaces of the masonry panel, but the mortar joints are in plain mortar; (iii) the reinforced mortar is placed both within the mortar joints and as a double reinforcing system on the external surfaces of each masonry panel. Experimental results show that in all the three cases the use of fiber reinforced mortar enhances both the shear strength and the post-peak capacity of the two-heads brick masonry panel. The most suitable behavior is related to panels reinforced with mortar both within the joints and as external reinforcing system. From the comparison between GFRM and BFRM it is shown that the best performance is related to basalt fibers mortar, that is also the most sustainable one. Authors always recommend the use of dispersed fibers within the mortar matrix, as it stands as effective strengthening system for new and existing masonry structures, above all when they are located in areas characterized by seismic hazard.

Experimental study of CRM-reinforced brick masonry panels: Cyclic shear-compression tests and compression tests

The preservation of the building heritage is often accompanied by the necessity of ensuring adequate structural safety of existing buildings. Existing masonry structures are usually characterised by a high seismic vulnerability due to their low tensile strength; moreover, despite the significant compressive capacity, often masonry panels are not able to guarantee the safety level required by the current building codes under gravitational loads, due to their slenderness and the possible out-of-plane actions. In recent years, several systems have been developed for the reinforcement of masonry buildings based on the use of composite materials externally bonded to the structural elements. Among them, the CRM system can be used for the static and seismic reinforcement of masonry piers as an alternative to the traditional reinforced plaster. The CRM system consists of the application on the panel surfaces of a mortar layer about 3 cm thick reinforced with a glass fibre grid and connected to the wall through transversal connectors. Despite its increasing use, to date, few experimental and theoretical studies have been carried out focusing on the lateral behaviour of reinforced panels, especially regarding their flexural response and drift capacity, as well as a little number of studies are available regarding the contribution provided by CRM layers on the buckling failure of panels induced by vertical loads. This work presents an experimental campaign carried out at the Laboratory of Structures and Materials of the University of Florence. A series of tests for the mechanical characterisation of materials composing the masonry and the reinforcement has been at first performed; then, quasi-static cyclic shear-compression tests and compression tests on solid brick masonry panels strengthened with CRM have been performed, considering the application of the CRM on a single or both faces of the walls. Tests allowed the assessment of the mechanical properties of the retrofitting system and its adhesion to the substrate and highlighted the advantages and limitations produced in the structural response of reinforced walls, both for horizontal and vertical loading.

Structural strengthening of masonry elements by reinforced repointing combined with FRCM and CRM

Within the framework of the seismic vulnerability of existing masonry constructions, a current issue is represented by the need of performing structural strengthening interventions to increase or restore the capacity of these buildings to resist seismic actions. Retrofitting solutions are therefore often proposed using innovative materials and techniques, such as Fiber Reinforced Cementitious Matrix (FRCM). It should be highlighted that the application of FRCM usually consists of a continuous reinforcing system covering the entire surfaces of the masonry panels. These strengthening solutions are very effective in improving the structural behavior of existing masonry elements, but they are not applicable when the surface of the masonry should remain visible, i.e., in historical buildings. Therefore, other techniques should be adopted, such as the reinforced repointing technique. In this paper, a series of diagonal compression tests are performed on clay brick masonry panels strengthened using different techniques, involving the use of reinforced repointing combined with the application of Fiber Reinforced Cementitious Matrix (FRCM) and Composite Reinforced Mortar (CRM). The tested masonry panels are strengthened either symmetrically, by using FRCM on both sides, or unsymmetrically, by applying the reinforced repointing technique on one side and FRCM or CRM on the other side of the panels. The results of the experimental campaign shows that the strengthening systems can improve the structural behavior of the masonry panels, both in terms of bearing capacity and ultimate deformations.

Shear strengthening of masonry walls with Textile Reinforced Mortars (TRM) under high temperature exposure

The behavior of masonry walls strengthened with Textile Reinforced Mortars (TRM) is a topic that has received considerable attention from researchers in recent years. However, the response of such elements after exposure to high temperature is an issue that remains to be explored extensively. This study analyzes the behavior of TRM-strengthened brick masonry panels with glass and carbon fiber meshes subjected to temperatures up to 600 °C, and subsequently tested under diagonal compression. The reinforcements were applied before or after temperature exposure, to analyze the effectiveness of damaged or undamaged TRMs, thus simulating different scenarios that might occur in a real building under a fire event. In general terms, the results showed that TRMs with carbon fibers exhibited a better response in these conditions, restoring the walls to their original capacity and providing additional ductility, whilst reinforcements with glass fibers seemed to be more affected by temperature. Finally, the experimental results are here compared to predictions from available design guides, in order to assess the accuracy that these codes would provide in these circumstances.

Statistical Assessment of In-Plane Masonry Panels Using Limit Analysis with Sliding Mechanism

Historical masonry structures have a great interest in civil engineering because they constitute a large part of the world’s building heritage. In this paper, the effects that different geometrical (panel ratio, block ratio, and bond type) and mechanical (friction ratio) parameters have on the in-plane structural response of brick masonry panels are investigated. A discrete modeling approach, based on a limit analysis and capable of reproducing sliding mechanisms, formulation by one of the authors has been adopted, enhanced, and implemented. Results, in terms of collapse multipliers and collapse mechanisms, are presented and analyzed following a systematic statistical approach. Statistically significant effects have been found for each factor considered. Furthermore, the statistical model adopted included nonlinear terms that allowed the identification of whether the effect of one parameter on the response depends on the level of any other parameters. Thus, it was observed that two-way factor interactions played an important role in the in-plane response of masonry panels. The panel ratio-friction ratio two-way factor interaction was the one with a more significant effect.

Masonry panels with external thermal insulation subjected to in-plane diagonal compression

Partial collapse of masonry facades during past strong earthquakes is well documented together with the increased vulnerability due to the presence of thermo-insulation within double wythe masonry. The combined seismic and energy retrofit of existing aged buildings represents a topic of importance for the building stock. The current study investigates the in-plane performance of a specific thermo-insulation scheme with panels attached on the external facades of multistory buildings. Diagonal compression tests of prototype specimens are done to study the influence of thermal insulation on the in-plane behaviour of clay brick masonry panels with or without thermal insulation. It was found that the thermo insulating attachment of the tested type performs in a satisfactory way when subjected to the stress field that arises to these masonry panels when subjected to diagonal compression. The thermo insolating panels, although finally debonded from the masonry substrate, do not collapse, even when the masonry panel develops large diagonal cracks, due to the presence of the used plastic anchors. The presence of such thermo insulating attachments leads to an increase of the in-plane load capacity and to a less brittle behaviour than the one without this thermo-insulation. This may also lead to a less vulnerable seismic performance than that of the same masonry panel without this thermo insulating attachment, although further validation is needed considering also the out-of-plane performance. The employed numerical modeling was successful in simulating the most important aspects of the in-plane response of the tested masonry wallets with or without thermo-insulating attachments. The good agreement with observed performance as well as the general nature of this numerical simulation confirms its validity.

TRM reinforced tuff and fired clay brick masonry: Experimental and analytical investigation on their in-plane and out-of-plane behavior

The paper presents the results of an experimental campaign aimed at investigating the in-plane and out-of-plane behavior of tuff and fired clay brick masonry panels reinforced by a commercial, not yet tested, Textile Reinforced Mortar (TRM) system. The TRM, consisting of hydraulic lime mortar coupled with a bidirectional glass fabric (total thickness of 30 mm), was applied on both sides of the panels and connected through stainless-steel helical bars. First, a mechanical characterization of the TRM system was carried out, according to recent guidelines (AC434 and CNR-DT215) by means of tensile tests and single-shear bond tests on the two different substrates. Then, the effectiveness of the reinforcement was investigated through uniaxial compression, diagonal compression and three-point bending tests on masonry panels. After that, experimental results were compared to the predictions of recent guidelines and analytical models available in the literature, by using the mechanical parameters obtained from the TRM mechanical characterization. TRM showed to be very effective in increasing the in-plane shear strength of tuff panels, of about 170%, whereas in the case of fired clay brick ones the increase was limited to 33%. Besides, the diagonal compression strength of reinforced specimens seemed to be strongly influenced by the mortar matrix, instead of by the fabric reinforcement, as it usually happens i.e. for Fabric Reinforced Cementitious Matrix (FRCM) systems. Thus, novel simplified analytical formulations to predict the shear strength of reinforced panels by only considering the contribution of the TRM matrix were provided, discussed and compared to current analytical approaches for FRCM systems. As regards the out-of-plane behavior, the TRM system significantly increased the out-of-plane bending strength and ductility of both tuff and fired clay brick panels. The applicability of current analytical approaches, as well as possible amendments, was also investigated. Finally, the compressive behavior of the walls was not substantially modified by the reinforcement, reasonably due to the low axial stiffness of the connectors and, to a minor extent, because they were dry inserted within the masonry and simply folded over the glass fabric.

In-plane shear strengthening of brick masonry panel with geogrid reinforcement embedded in bed and bed-head joints mortar

An experimental investigation was carried out to study the strengthening performance of brick masonry prisms and panels via geogrid reinforcement embedded in brick mortar. A compressive strength test was performed for brick prisms, while a diagonal compression test was performed for brick panel with two patterns, i.e., geogrid reinforcement at bed joints as well as at bed-head joints. The compressive strength of the geogrid embedded prisms was found to be 32.65% more than that of un-reinforced brick prisms. While, geogrid-reinforced brick panels exhibited better crushing load, in-plane shear strength, lateral strength, ductility, etc., than un-reinforced masonry with the highest in-case of bed joint reinforcement. Cost analysis showed that the unit costs of un-reinforced and reinforced walls are similar (within 6.5%). Thus strengthened walls can be valid alternative to un-strengthened walls for new constructions and a low-cost strengthening technique for earthquake disaster mitigation of brick masonry buildings.

Geosynthetic as Sustainable Materials for Earthquake resistant of Masonry Structures

When exposed to simultaneous in-plane and out-of-plane behaviour generated by earthquakes or high wind pressure, unreinforced masonry (URM) walls are vulnerable to failure. The paper presents the performance of brick masonry panels using non-woven geotextile in-plane shear and out-of-plane bending experimentally tested. The panels were reinforced with a diagonal geometric pattern on both sides. From the laboratory assessment, it was determined that geosynthetic enhancement significantly improved the capacity of load carrying, displacement capacity, bending moment, stiffness, diagonal shear, in-plane shear, and flexural strength with higher performance for both cases in the case of the cross pattern. In contrast to the un-strengthened panel, experimental findings have demonstrated a less fragile behaviour. Geosynthetics can therefore be preferably suited for strengthening the brick masonry panel in order to defend brick constructions in seismic populated places.

Geosynthetic as a strengthening material for brick masonry wall

Geosynthetic products have been utilized widely in numerous Civil Engineering construction. The paper presents performances of in-plane shear for brick masonry panels strengthened with two varieties of geosynthetics. The walls were strengthened with geotextile surface wrapping using epoxy resins and geogrid reinforcement at the bed joints embedded in brick mortar. These panels were subjected to a diagonal compression test for determined the in-plane shear strength. From this study,it had been determined that the load-carrying capability can be increased with the strengthening of geotextile and geogrid, stiffness, displacement capability, with respect to the un-strengthen wall. It was also observed that the shear strength under diagonal loading and in-plane strength increased both for surface wrapping and bed joint reinforcement. Furthermore, an increase in in-plane shear strength was more in case of geogrid reinforcement (43%), than surface reinforcement (29%), when compared to unstrengthened walls. The economy index showing a low-cost technique for strength enhancement of brick walls in earthquake-prone areas.

Performance of Ferro-Cement Strengthened Unreinforced Masonry Walls against Reverse Cyclic Loading

Unreinforced masonry (URM) buildings constitute a significant part of existing buildings in Sri Lanka and especially in the south-eastern region because it is low cost and easy to construct. Past ground tremors had shown that these buildings are highly vulnerable to seismic and ground vibration due to the low strength of brick masonry. In the last two decades, several seismic retrofitting techniques for masonry buildings have been developed and practiced, but rarely validated with experimental results and numerical modelling. The purpose of this study is to develop a seismic retrofitting technique to be adopted with locally available materials and an easy retrofitting method suitable for the particular masonry structures. Brick masonry panels (600 x 640 x 215mm) were cast and cyclic loading tests were carried out for two types of walls: walls without applying retrofitting technique and walls retrofitted with Ferro-cement belts. Ferro-cement belts have been increasingly used owing to the strength, easy application and low cost. Here, the effect of different retrofitting configurations with Ferro-cement coating on the in-plane cyclic performance of brick walls with openings was examined. Experiments conducted in this study revealed that Ferro-cement belt retrofitted walls horizontally and vertically significantly increased its in-plane strength and ductility capacity.

Strengthening of Unreinforced Brick Masonry Panel Using Cast-in-Place and Precast Textile-Reinforced Concrete

ABSTRACT Textile-reinforced concrete (TRC) has found extensive attention as a promising material for structural strengthening of masonry structures. In the present paper, a first-of-its kind of the study of bonding of precast TRC laminates was compared with cast-in-place TRC strengthening for masonry wall panels. TRC consists of a high early strength developing binder and an alkali-resistant glass textile reinforcement. Characterization studies were carried out to determine the strength development pattern for the binder as the age progresses. Uniaxial test has been carried out to understand the tensile behaviour of TRC that has implications in structural strengthening. Based on the studies, an optimal textile reinforcement ratio and the corresponding number of layers of textile to be used in the TRC have been arrived for strengthening of brick masonry panels. Strengthened and unstrengthened brick masonry panels were experimentally tested under the combined effect of axial compression and shear. The results indicate that there is an increase in stiffness, ultimate load and a significant reduction in the lateral deflection for the strengthened panels compared to unstrengthened panels. Brick masonry strengthening methodology using precast TRC laminates bonding exhibited promising results compared to cast-in-place TRC strengthening.

Brick masonry panels strengthened with textile reinforced mortar: experimentation and numerical analysis

Composites materials comprising textiles embedded in organic or inorganic matrices are receiving great attention for their aptitude to be effectively applied as strengthening systems in existing structural components. The use of a Basalt Textile Reinforced Mortar (BTRM) composite to improve the in-plane shear behavior of brick masonry panels is here studied. The reinforcement is externally bonded to the masonry substrate. An experimental campaign is carried out involving diagonal compression tests on specimens strengthened with the BTRM system applied on one and both panel surfaces, experiencing asymmetric and symmetric reinforcement. The experimental response of unreinforced and reinforced panels is analyzed in terms of stress-strain curves, strength, stiffness and deformation capacity, crack pattern and failure mode. The experimental results are also compared with those obtained from a previous campaign carried out by the authors on tuff masonry panels reinforced with the same BTRM system, with the aim to investigate its effectiveness when applied to different masonry types. Finally, a relatively simple numerical model, suitably calibrated, is used to interpreter and analyze the results of the experimental investigation, leading to a validation of the model itself.

Can Textile Reinforced Mortar (TRM) Systems Be Really Effective to Increase Compressive Strength of Masonry Panels?

The use of Textile Reinforced Mortar (TRM) systems represent a valid alternative to traditional strengthening techniques, to improve mechanical strength and seismic performance of masonry buildings. Their effectiveness has been validated by several studies [1-4]. However, the TRM contribution in the mechanical behavior of masonry walls, subjected to simple compression, has not yet been fully investigated. In this study, an experimental campaign with the objective of studying the efficiency of TRM systems, applied to clay brick masonry panels, is presented. Compression tests were conducted on clay brick masonry panels with dimensions of 250x1000x1200 mm3. Glass fiber bidirectional fabrics were applied on both sides of the panels, coupled with lime-based mortar, and connected with stainless steel helical connectors. The total thickness of the reinforcement system is 30 mm. The effect of the TRM reinforcement on the mechanical behavior of the panel is analyzed and experimental results are compared with those of unreinforced panels in terms of ultimate strength and failure modes.

Experimental In-Plane Shear Capacity of Clay Brick Masonry Panels Strengthened with FRCM and FRM Composites

Unreinforced masonry (URM) buildings, largely found in Euroasian regions, are particularly vulnerable to in-plane shear failures during seismic events due to the poor shear capacity of masonry walls. In the case of historical masonry buildings, the use of strengthening solutions with polymeric and polymer-modified matrices composites is not recommended since the breathability of the masonry could be reduced, leading to a fast and undesired degradation. In this paper, an innovative fiber-reinforced cementitious mortar (i.e., FRCM) system was used to improve the shear capacity of old-type solid clay brick masonry walls. An experimental program on 24 masonry panels subjected to diagonal compression tests was carried out. The innovative FRCM system consisted of a basalt grid embedded in an improved inorganic matrix, made of lime-based mortar reinforced with short glass fibers (i.e., Fiber-reinforced mortar, FRM). Two sets of specimens were tested, single-leaf masonry panels and double-leaf masonry panels, to investigate the typical configurations of load-bearing walls and partition walls. The effectiveness of the innovative FRCM system was investigated for both a conventional symmetric strengthening configuration and an asymmetric strengthening configuration with anchors, a solution often adopted in the case of internal/external interventions only. Furthermore, the response of masonry panels strengthened with only symmetric FRM with a slightly greater amount of short glass fibers embedded in the matrix was also investigated. The experimental outcomes outlined that panels reinforced with symmetric FRM achieved similar effectiveness in the shear strength increase to panels reinforced with symmetrical FRCM. Conversely, a reduced deformability was observed in FRM panels with respect to those strengthened with FRCM. The experimental results also allowed the quantification of the effectiveness of FRCMs in the case of asymmetric strengthening configurations. Finally, a comparison between experimental results and American Code provisions for FRCM-strengthened systems was reported.

Experimental work for mechanical properties of brick and masonry panel

The use of Masonry panels in building construction has been popular in most of the parts of the world. However, the use of bricks and brick masonry in different parts of the world being of different nature in terms of quality, size, workmanship of construction, etc. It is yet a topic of interest to researchers to identify the mechanical properties, like Young’s modulus of elasticity and shear modulus of brick masonry panels. It is essential to know the characteristic of brick masonry panels in order to evaluate the responses of masonry walls for any kind of loading. Individual bricks do possess better compressive capacity as compared to masonry walls. Masonry walls are bound together with either mud mortar or by cement sand mortars of various mixes as per the strength requirements. The essential strength properties in engineering are basically the compressive strength and the modulus of elasticity. The American Society for Testing and Materials (ASTM) standard is the most popular for testing bricks and brick masonry for these properties so far. Here, the study has been concentrated in finding the compressive strength of brick, mortar and brick masonry. The study is also done for Young’s modulus of elasticity of brick as well as that of masonry wall. Similarly, the study is extended to find the modulus of rigidity of brick masonry panel. The study is done experimentally for the samples that are generally used in Kathmandu, Nepal. The samples include bricks, cement and sand particularly available in Kathmandu region.

Experimental investigation of in-plane shear behaviour of grey clay brick masonry panels strengthened with SRG

Textile reinforced mortar (TRM) composites have received much attention as they are a superior sustainable material and physically compatible with masonry and historical structures. Among the numerous materials used in TRM composites, steel reinforced grout (SRG) which is produced with high strength steel cords embedded in a cementitious mortar matrix, demonstrates exceptional mechanical performance at a relatively low cost. In this paper, an experimental investigation is carried out on their use as in-plane shear reinforcement of masonry wall panels. The masonry panels are constructed with grey clay bricks (GCBs), a unique construction material widely used in traditional Chinese architecture. Diagonal compression tests are carried out on two unreinforced panels and six strengthened panels with different reinforcement configurations. The contribution of the SRG system to strengthening is assessed by examining the shear stiffness, shear strength, ductility under shear, and changes in failure mechanisms. A comparative analysis is carried out by using results from the previous literature, and the analytical methodologies and the practical use of the SRG system are also discussed.

Behaviour of in-plane loaded masonry panels

The interest of the scientific community for the seismic behaviour of existing masonry buildings has largely increased in recent years, due to the fact that the seismic events have evidenced a great need of rehabilitation. Masonry structures, and especially low rise buildings, are in fact the most diffused all over the world and in particular in seismic areas in developing countries because of their ease in construction and economy. Moreover unreinforced masonry is the most diffused construction material in the major part of historical centrers in Europe. In a well engineered and constructed masonry building subjected to earthquake forces, in which out of plane mechanisms can be avoided, the contribution of in-plane shear resistance of the masonry walls is a determinant factor for the stability of the whole structure. Based on this last consideration, this paper presents an approach for the analysis of masonry walls loaded with in-plane forces, involving a minimum energy procedure. The results of the numerical analyses presented are compared with those obtained by laboratory tests on brick masonry panels.

In-plane strength of masonry panel strengthened with geosynthetic

The in-plane strength of solid clay brick masonry panels strengthened with non-woven geotextile was studied numerically and experimentally. The panels were strengthened on one side with different geometric pattern viz. parallel, diagonal and cross. These panels were subjected to diagonal compression. Finite element modelling with the micro non-linear model is used in the analysis to simulate the in-plane behaviour of masonry panels with and without strengthening. From the study, it was observed that geosynthetic strengthening increased the load carrying capacity, shear strength, in-plane strength and stiffness remarkably with better performance in case of the cross pattern. Experimental results also showed a less brittle behaviour when compared to the un-strengthened panel. Hence, geosynthetic can be ideally used for strengthening of the brick panel to protect the brick buildings in seismic active areas.

Seismic Retrofitting of Unreinforced Brick Masonry Panels with Glass Fibre Reinforced Polymers

The out-of-plane performances of brick masonry panels with different retrofitting patterns using glass fibre reinforced polymers (GFRP) have been studied under three-point loading test. The panels were retrofitted on one side and both sides with different geometric configurations. The retrofitted specimens increased the failure load from 19.6 kN (UR) to 79.2 kN. It was observed that the flexural strength of the retrofitted patterns increased from 31.58% to 150% when compared to un-retrofitted specimens. Also, the bending moment of the retrofitted panels increased from 5.94 kNm to 8.96 kNm when retrofitted with one side, while it goes up to 14.88 kNm when retrofitted with both side as compared to un-retrofitted specimens. Further, it also observed that the panel with cross retrofitting showed more efficiency in terms of flexural strength, bending moment, stiffness and deformation capacity.