Brick Mortar Interface Research Articles

Crack patterns in masonry structures using phase field method

This work aims to study the crack pattern in masonry-like structures by a simplified description of the mediumusing a variational damage model. In literature, when modeling fractures in masonry structures, capturingboth fracture types, cracks in units, and cracks at the interface simultaneously, usually requires a complicated scheme. The phase-field method has been widely used recently because of its robustness in capturing variousfracture types. In this work, we consider the mortar and the interface (between the mortar and units) as a thickinterface layer with pseudo-material properties. We conduct numerical tests on a bending beam and a tensilewall using strategies of material properties with a phase field model. As it is not distinguished the crack in themortar and the brick-mortar interface, it is shown in this work that both types of fracture, in the thick interfacelayer and the unit, can be captured just using the phase field method and the simplified micro model.

Widely Employed Constitutive Material Models in Abaqus FEA Software Suite for Simulations of Structures and Their Materials: A Brief Review

The structural response of masonry/concrete structures depends upon the load-carrying mechanism and subsequently deformations produced by loads carried. In masonry/concrete structures, identification of the stress/strain imposing stress conditions and strain hardening/softening makes the structural response more complicated. Elastic damage models or elastic-plastic constitutive laws are inadequate to simulate masonry/concrete response under high strain-rate loadings. Further, irreversible or plastic strain cannot be realized using the elastic damage model. Several constitutive damage models are available in the literature. In this article, a concise explanation of the functioning of different material models in the Abaqus software package has been provided. These models include concrete damage plasticity for concrete and masonry, traction separation constitutive laws for brick-mortar interface, Hashin's criteria for CFRP, Johnson-Cook plasticity for steel, and crushable foam plasticity hardening for metallic foams. Researchers frequently utilize these models for numerical simulations and modeling of infrastructural elements and their respective materials when subjected to various structural loads. Besides, this paper presents a discourse on problem-solving methods and a comparison between explicit and implicit analysis. The research provides valuable input to researchers and practitioners in the field of structural engineering for an in-depth understanding of the functioning of Abaqus' pre-existing material models.

Hygrothermal properties of hollow brick masonry used in veneer

The material properties of a brick masonry are important when modelling or comparing different veneers. The effect of mortar joint, however, is somewhat an unknown variable. In this study, two different firing batches of a hollow burnt-clay brick product were tested for thermal conductivity, water vapor permeability, water absorption coefficient and capillary moisture content. Brick and mortar materials were tested both exclusively and as masonry specimens. The effect of brick-mortar interface was within margin of error for the first brick batch with slightly lower density, while batch two water vapor permeability, water absorption coefficient and capillary moisture content were noticeably affected. The effect of brick-mortar interface seems to be dependent on brick properties. The differences in hygric properties between brick batches were large, but below 100 %. Accounting for mortar using area weighted properties can improve modelling accuracy, but other factors such as workmanship, degradation and brick batch differences are likely more important.

Simulation of moisture transport in fired-clay brick masonry structures accounting for interfacial phenomena

This paper presents a numerical study on moisture transport in brick masonry walls with a special focus on the simulation of their hygric performance as well as the hydraulic phenomena at the brick-mortar interface. A diffusivity model based on Fick's law is used to describe the moisture transport accounting for both liquid and water vapor movement. The necessary hygric parameters are obtained directly from experimental tests or determined by curve fitting. The proposed model is validated with respect to water absorption and drying tests. The good-fitness of the results is qualitatively assessed and an overall good agreement is found between the simulated and measured curves. It is demonstrated that the chosen liquid water diffusivity expression needs to be adjusted to represent drying processes; the necessary adjustment is made through a diffusivity factor implemented in the original analytical expression. The interface impact on water absorption is introduced as a hydraulic resistance. Moreover, it is hypothesized that the presence of successive interfaces entails an additive in-series effect. Conversely, the interfacial impact on drying is negligible. Finally, the proposed model is extended to different modeling approaches commonly used for mechanical studies of masonry. The necessary input data, modeling methodology, advantages and disadvantages associated with each modeling strategy are also discussed. The present study points out the need of studying water absorption in multi-layered structures made up of constituents with relatively similar hygric behavior. In such cases, the impact of imperfect contact at the interface between materials is not negligible.

An experimental study on the mechanical properties of solid clay brick masonry with traditional mortars

An experimental study is carried out to investigate the mechanical properties of clay brick masonry fabricated using traditional mortars. In this regard, four types of mortar whose frequent uses in Iranian traditional and historical monuments have been reported in the literature are selected. These mortars are gypsum mortar and three types of lime-based mortars including, Sarooj, lime-sand mortar, and lime-cement-sand mortar. In this study, tests on brick units, mortar specimens, masonry prisms and wallettes are conducted. The compressive stress-strain behavior, compressive strength, elastic modulus, and rupture modulus of mortars are determined from the standard tests. Moreover, the compression test of masonry prisms, direct shear test of brick-mortar bond, and diagonal shear test of masonry wallettes are carried out. The compressive stress-strain behavior of masonry and the shear bond strength of brick-mortar interface are determined from the tests on masonry prisms. Furthermore, shear stress-strain behavior of masonry wallettes is evaluated through diagonal shear tests. Some key mechanical properties of masonry wallettes such as modulus of rigidity and Poisson's ratio are also found from the test results. Accordingly, the brick-mortar bond governed the in-plane shear behavior of the masonry wallettes in diagonal shear tests. Furthermore, the highest compressive strength, elastic modulus, and diagonal shear strength belong to the masonry fabricated with gypsum mortar. By using the results of the experimental program, the applicability of some well-known empirical formulations for estimating the compressive strength of masonry prisms as well as the accuracy of idealized stress-strain models proposed for masonry material, are assessed.

Multiscale assessment of masonry materials from the roman imperial baths at Sagalassos

The Imperial Roman Baths in Sagalassos, Turkey, were built in the 2nd century C.E. and have been excavated since the 1990s. The harsh environmental conditions, especially during the winter, resulted in the accelerated decay of the building materials, material losses, and serious structural problems in the Baths. This study explores the comprehensive characterization and multiscale assessment of bricks and mortars for effective preservation of the Baths. Experimental results showed that although the interface between building materials weakened after years of accumulated degradation, the individual materials still had higher strength than those from the same period. The material scale finite element model used to understand the damage mechanism showed that brick failure was caused by the tensile stresses accumulated at the brick–mortar interface when some of the mortar crumbled and fell with deterioration. A global sensitivity analysis was also conducted to investigate the impact of individual layer thicknesses on the stress distribution in the brick and mortar composite. Results indicated that thicker bricks resulted in better confinement at mortar layer and smaller tensile stresses at the bricks.

Use of Quarry Dust in the Binding Mortar and Its Effect on Mechanical Characteristics of Brick Masonry

The strength characteristics of masonry is greatly affected by the brick strength, mortar strength and bond between brick-mortar interface. Especially, binding mortar significantly affects the shear and flexural strength of the masonry. In conventional masonry construction, river sand or natural sand is mixed with cement and used as binding mortar. However, due scarcity of good quality river sand, the extensive focus is on finding alternative materials for river sand for construction purposes. Quarry dust is one of the best alternatives for river sand, which can be used as fine aggregates in binding mortar. This study investigates the strength characteristic of the masonry made of quarry dust incorporated binding mortar instead of conventional cement-sand mortar. The binding mortar with four different river sand replacement levels of 0%, 33.3%, 66.7% and 100% quarry dust, was used for construction masonry. Compression test, direct shear test and cross-couplet test were conducted to evaluate the strength characteristic. The test results revealed that compressive, shear and bond strength of masonry was improved with increased quarry dust content in the binding mortar.

Numerical modeling of a masonry arch structure

To investigate the structural behavior and estimate the strength capacity of masonry arch structures, experimental testing can be challenging at large scales. In such a case, numerical modeling is considered as an interesting alternative. In this work, two ready-to-use modeling techniques are proposed. The first one is based on the detailed micro-modeling in which the brick and mortar were modeled using concrete damaged plasticity model and the brick-mortar interface was modeled by the surface-based cohesive behavior model. These constitutive laws are already implemented in the ABAQUS environment without the need for specific subroutines. The second technique is based on the homogenization approach to derive the equivalent characteristics of masonry, which is then modeled as one continuous element. Both techniques were used to simulate the experimental behavior of a masonry arch subjected to in-plane bending. Finally, comparison between experimental and numerical results of the two methods shows the capability of the proposed homogenization approach to simulate the behavior of masonry arch structures with a sufficient degree of accuracy and a reduced computational cost.

Experimental characterization of moisture transport in brick masonry with natural hydraulic lime mortar

This article presents an experimental study on the hygric performance of brick masonry with a special focus on the hydraulic characterization of the brick-mortar interface. The hygric behavior was studied at the level of the constituent materials as well as at the composite scale. An extruded fired-clay brick and two types of mortar –Portland cement mortar and natural hydraulic lime mortar– were chosen as target materials. The hygric properties were determined following prescribed experimental procedures. The experimental program included vacuum saturation tests, static gravimetric tests for adsorption/desorption isotherms, dry/wet cup tests, capillary absorption tests, and isothermal one-dimensional drying. The results allowed for a comprehensive identification of the main hygric features of the target materials. Fired-clay brick and lime mortar revealed low hygroscopicity and a strong capillary-active behavior with negligible hysteresis, whereas cement mortar showed activity in both hygroscopic and capillary ranges with a distinct moisture storage hysteresis. Different curing conditions led to dissimilar properties between the lime mortar prepared in molds and the same mortar cured in masonry bed joints. Water absorption in fired-clay bricks showed a marked anisotropic behavior, likely derived from the extrusion process. The existence of an imperfect hydraulic contact at the brick-mortar interface was demonstrated for water absorption. Conversely, the interfacial effect on drying kinetics was not evident.

A critique on characterising interface resistances with maximum moisture flows

In February 2018, this journal published the article “Interface influence on moisture transport in buildings”. This critique firstly establishes that the reported ‘hydric resistance’ values overestimate the impacts of the material interfaces for the brick–mortar ‘hydraulic contact’ samples. It is shown that the actual flows after crossing the brick–mortar interface are 2 to 5 times higher than indicated by the article’s ‘hydric resistance’ values. This critique secondly demonstrates that the article’s main idea of characterising material interfaces with a maximal post-interface-flow is not dependable nor generalisable. This flow is not necessarily constant in time, and may depend on the interface’s actual location, the surrounding materials’ properties and the imposed boundary conditions, hence defying all generalisation. The conclusion of this critique is therefore that the processing methods and results of the disputed article are not reliable.

Numerical analysis and experimental characterisation of brick masonry

Simulating the mechanical behaviour of masonry structures by using numerical analysis is still a complex subject because the process is hindered by little knowledge of the properties of masonry constituents and the interface. In particular, the definition of mechanical properties of masonry components is a key issue when finite element analysis is adopted for the prediction of the mechanical behaviour of masonry walls under accidental and exceptional loads. In an attempt to develop a detailed micro-modelling of brick masonry under compression, where the brick unit, mortar and brick-mortar interface are defined by their corresponding mechanical properties obtained through experimental testing, this work presents experimental tests on brick units, mortar and small masonry cubic specimens. Hence, a detailed micro-modelling of brick masonry cubic specimen is developed in ABAQUS. The numerical model is calibrated and validated based on the results obtained from the experimental tests on masonry cubic specimens. The results show that the numerical model is able to predict the mechanical behaviour of the masonry specimen with 95% accuracy in terms of compressive strength.

Numerical analysis and experimental characterisation of brick masonry

Simulating the mechanical behaviour of masonry structures by using numerical analysis is still a complex subject because the process is hindered by little knowledge of the properties of masonry constituents and the interface. In particular, the definition of mechanical properties of masonry components is a key issue when finite element analysis is adopted for the prediction of the mechanical behaviour of masonry walls under accidental and exceptional loads. In an attempt to develop a detailed micro-modelling of brick masonry under compression, where the brick unit, mortar and brick-mortar interface are defined by their corresponding mechanical properties obtained through experimental testing, this work presents experimental tests on brick units, mortar and small masonry cubic specimens. Hence, a detailed micro-modelling of brick masonry cubic specimen is developed in ABAQUS. The numerical model is calibrated and validated based on the results obtained from the experimental tests on masonry cubic specimens. The results show that the numerical model is able to predict the mechanical behaviour of the masonry specimen with 95% accuracy in terms of compressive strength.

Improvement in lateral resistance of mortar-free interlocking wall with plaster having natural fibres

Housing deficiency and population increase around the globe has led to a search for more cost effective, environment friendly, easy and fast ways of construction. Out of many technologies found, mortar-free interlocked masonry systems were developed to eliminate the deficiency of traditional masonry like poor workman ship, weak brick-mortar interface etc. For such systems against earthquakes, lateral resistance can be enhanced with plaster. But there is a need to further improve the performance of plaster in mortar-free interlocking walls for better ductility. Therefore, in this study, non-plastered wall (as a datum) was compared with plain and fibrous-plastered masonry walls using natural fibres like rice straw and sisal fibres. 2% fibres (by mass of cement) was used. 2200 mm high interlocked block masonry walls (mostly used in poor developing countries) were experimentally tested for out of plane resistance. The research aim was to evaluate the mechanical and dynamic parameters like elastic stiffness, first crack load, energy dissipation, toughness index, frequency and dynamic stiffness. Detail discussion was made on fibrous plaster behaviour. Analytical design flow chart was also developed to evaluate the lateral resistance of the fibrous plastered masonry walls. Sisal fibre reinforced plaster was found better than rice straw reinforced plaster. The factor of increase in peak load, elastic stiffness, energy absorption and toughness over datum was found to be up to 229%, 14 times, 395% and 127%, respectively, for sisal fibre reinforced plastered walling system.

Shear strength of brick mortar interface for masonry in Lima city

Masonry structures constitute a large proportion of the building inventory in Lima and in most cities in Peru, mainly because of their benefits in terms of low cost, good mechanical properties and easily worked. It was observed in the cyclic loading test of masonry walls carried out at CISMID that the modes of failures can be mainly generated by shear forces. Based on the previous information, it is known that diagonal cracking and slip of the mortar-brick joints are the dominant failure mechanisms of confined masonry walls. 
 In order to determine the mechanical behavior in the mortar-brick joint, an experimental program was carried out, by using industrial and handmade bricks. The test specimens were specifically designed to transmit pure shear along the bed joints under certain constant levels of compressive stress normal to the bed joint. The results of experimental shear tests are presented and discussed. It is then found a consistency between the behavior of masonry joints under shear with the Mohr Coulomb criterion. The shear failure capacity was influenced by the brick type, pre-compression load level and mortar type. It is also noticed in this experimental study that the pre-compressive stress normal to the bed joints significantly increase the shear strength of the mortar-brick joint.

Cohesive-frictional interface fracture behavior in soft-brick masonry: experimental investigation and theoretical development

An experimental investigation into the shear transfer across the brick mortar interface at different levels of applied pre-compression is reported. Direct shear tests are performed in the triplet test configuration on masonry made with a soft brick. The failure across the brick–mortar interface is progressive and is produced by a crack in the brick–mortar interface. The interface crack propagates in a thin layer where the mortar penetrates the brick. A cohesive-frictional interface relationship which combines progressive cohesive failure with increasing frictional resistance is developed. The maximum shear resistance obtained from the cohesive-frictional relationship follows a Mohr–Coulomb type relationship. The residual frictional resistance increases linearly with an increase in the applied compression.

Reliability analysis applied to structural ceramic blocks

Abstract The Brazilian National Standard for structural masonry considers the compressive strength as the most important factor for design of structures. For the use of ceramic blocks, NBR 15812-1 (ABNT, 2010) recommends that the prism/wall efficiency factor should be at least 0.70. For that, it is important to assess the geometrical and mechanical properties of blocks and the mechanical properties of mortar, as the failure mechanism of prisms is associated with internal stresses in the brick-mortar interface. Although this design strategy has been successfully implemented, it does not consider a series of uncertainties in the production of the block and in the masonry construction process. Taking this into consideration, this paper aims to provide a statistical and reliability assessment of blocks produced by a specific manufacturer, between February and April 2014. Experimental measurements and tests provided data to a statistical characterization of dimensional parameters and compressive strength. A reliability-based evaluation was then carried out to describe the probabilistic performance of masonry subjected to compression by using First Order Reliability Method (FORM) and Monte Carlo simulation.

Assessing the influence of self-healing capacity of lime-based mortars on brick-mortar interface strength in masonry units

Among the materials used in constructions, self-healing ones have been widely studied, including polymers, asphalts, cement binders; nonetheless the issue of the implementations and engineering of the self-healing capacity of lime-based mortars has been seldom investigated. As a matter of fact, the aforementioned capacity in restoration of building heritage, as well as in concrete structures, would provide an interesting contribution in terms of durability of the same restoration work as well as of the building as a whole. The aim of this research is to study the influence of healing capacity on the masonry behaviour by means of shear tests. The choice to perform shear tests, with or without lateral precompression is due to the representativeness of conditions truly occurring in masonry structural elements when in service. “Triplet specimens” have been fabricated, consisting of 3 clay bricks and 2 layers of purposed-design mortar, to mimic the compositions of mortars which can be actually found in existing heritage buildings. The methodology envisages three phases: a first series of specimens, after 28 days curing in lab environment, was tested to evaluate the shear strength. Then, on a second series of samples, a damage was induced by loading them to a prescribed fraction (70%) of the shear strength, determined as above in the previous stage; samples were subsequently immersed in water for 3 months and re-tested at the end of this curing period. Results clearly show that the autogenous healing capacity is responsible of an interesting recovery of the interface shear strength. The reliability of this approach has been also investigated by comparing the experimental results with a simplified FE model.

Experimental investigation of compressive failure in masonry brick assemblages made with soft brick

An experimental investigation of compressive failure in masonry made of soft clay bricks is presented. Masonry assemblages are tested to evaluate the influence of the relative strength of mortar on the observed damage evolution and compressive failure. Damage evolution associated with the formation and propagation of vertical splitting cracks during the compressive load response of masonry assemblages in the stack bonded arrangement are studied using a full-field optical technique based on digital image correlation. Using image correlation, clear evidence of the crack forming in the mortar and propagating into the brick is established. Damage is associated with cracking in the mortar due to lateral tension produced by the confined expansion of brick. Failure depends upon the tensile strength of the mortar. In mortar with lower strength than the brick unit, failure is produced by spalling associated with multiple cracks, which results in a loss of load bearing area. For mortar with a higher strength than the brick, cracking occurs when the level of compression is a significant proportion of the compressive strength of the brick material. Localized crushing resulting from localization of strain in a small region at the brick–mortar interface is produced at axial stress close to the unconfined compressive strength of the brick material. Failure in the case of high strength mortar is a result of the localized crushing and the resulting global instability.

Masonry infilled reinforced concrete frames under horizontal loading / Stahlbetonrahmen mit Ausfachungen aus Mauerwerk unter horizontalen Belastungen

AbstractThe behaviour of infilled reinforced concrete frames under horizontal load has been widely investigated, both experimentally and numerically. Since experimental tests represent large investments, numerical simulations offer an efficient approach for a more comprehensive analysis. When RC frames with masonry infill walls are subjected to horizontal loading, their behaviour is highly non‐linear after a certain limit, which makes their analysis quite difficult. The non‐linear behaviour results from the complex inelastic material properties of the concrete, infill wall and conditions at the wall‐frame interface. In order to investigate this non‐linear behaviour in detail, a finite element model using a micro modelling approach is developed, which is able to predict the complex non‐linear behaviour resulting from the different materials and their interaction. Concrete and bricks are represented by a non‐linear material model, while each reinforcement bar is represented as an individual part installed in the concrete part and behaving elasto‐plastically. Each brick is modelled individually and connected taking into account the non‐linearity of a brick mortar interface. The same approach is followed using two finite element software packages and the results are compared with the experimental results. The numerical models show a good agreement with the experiments in predicting the overall behaviour, but also very good matching for strength capacity and drift. The results emphasize the quality and the valuable contribution of the numerical models for use in parametric studies, which are needed for the derivation of design recommendations for infilled frame structures.

Lattice simulations for evaluating interface fracture of masonry composites

The brick–mortar bond is often the weakest link in the masonry composites. The localization of fracture processes at this bi-material interface plays an important role in the failure of this assemblage. These micro-level fracture processes control the nonlinear behavior of the brick–mortar interface which significantly affects the global behavior of the masonry structure in the continuum macro level. This study focuses on 2-D lattice-based fracture simulations to characterize progressive debonding of brick–mortar interfaces and to determine fracture properties in unreinforced masonry composites. Using the fundamental argument of Griffith which transforms potential energy into surface energy, lattice erosion is used to determine the critical energy release rate and other fracture quantities from basic strength properties of lattice struts that are removed upon failure. This micro-level information serves to upscale the lattice fracture arguments onto the meso-scale to quantify the fracture energy of traction-separation cohesive zone models in the context of continuum F.E. simulations of heterogeneous media like masonry.