Deformation Of Masonry Research Articles

Wind loads tests of external walls blocks masonry of noncombustible polystyrene concrete

Introduction. Blocks of non-combustible polystyrene concrete of D300 density grade, B1 compressive strength class with normalized thermal conductivity λ0 = 0,078 W/(m·°C) and frost resistance grade not lower than F75, developed by LLC “Institute VNIIZhelezobeton”, were used in masonry with a thickness of 375 mm without special fireproof lining. Such masonry successfully passed standard fire tests for fire hazard and fire resistance, which showed the possibility of its use in external non-bearing energysaving walls of multi-storey buildings (up to 25 floors inclusive, about 75 m high).Aim. Evaluation of the strength and deformation characteristics of non-combustible wall masonry made of noncombustible polystyrene concrete blocks with a density of D300 at design wind loads at a height of about 75 m. Materials and methods. Fragments of uncoated wall masonry 375 mm thick, 2,7 m high and 1,2 m wide of noncombustible polystyrene concrete blocks mounted on a mortar with over-all dimensions of 295 × 375 × 595 mm were tested.The test procedure is in accordance with State Standard 8829-2018.Results. The destructive bending load exceeded the calculated one by an average of 4,1 times, while the deflection in the middle of the fragment was 1,9 times less than the permissible one.A methodology has been developed for calculating the strength and deformability of masonry of polystyrene concrete blocks under wind loads, taking into account the influence of horizontal and vertical masonry joints, which is scheduled to be reflected in Amendment No. 1 SP 434.1325800.2018.Conclusions. The results of wind load tests showed that for unlined masonry made of non-combustible polystyrene concrete blocks with a density of D300 and a thickness of 375 mm, the requirements for strength and deformability are met with a significant margin. The results of tests for wind and fire effects of the specified block masonry make it possible to use it in nonbearing external walls of multi-storey residential energyefficient buildings up to 75 m high in virtually all regions of Russia.

Damage of Infill Masonry Walls due to Vertical Loads in Buildings with Reinforced Concrete Structure

Buildings are subjected to deformations of their reinforced concrete structure due to vertical loads that can lead, in certain cases, to the significant cracking of the unreinforced masonry (URM) infill walls, therefore requiring the development of specific knowledge of these types of deformations in order to minimise them. Aiming the evaluation of buildings with reinforced concrete structures subjected to vertical deformations, the mechanical characteristics of their infill masonry walls, as well as of their interface with the supporting concrete elements, are here analysed. The basic compression behaviour of brick masonry is assessed particularly through the previous analysis of a vertical compression test of a masonry specimen. The mechanical behaviour characteristics of the constituents (bricks, and mortar joints) are analysed to account for their influence on the compression behaviour of masonry infill, aiming particularly for the prevision of their cracking in case of vertical deformations of the supporting reinforced concrete (RC) elements. Based on that evaluation, the analysis of masonry walls subjected to vertical deformations of their supports is made through the assessment of the relevant characteristic behaviour of masonry wall-beam/slab assembly in case of vertical load. A general modelling approach of the behaviour of URM infills and the interaction with their supports is generally accessed. Finally, the preventive control of deformations of masonry wall-beam/slab assembly is discussed.

Deformation approach to the calculation of compression resistance of reinforced stone elements

Introduction. When calculating stone and reinforced stone elements, only the limiting stage before destruction is considered, the nonlinearity of deformation of materials and, accordingly, the redistribution of forces between masonry and longitudinal reinforcement in cross sections are not taken into account. A deformation approach to the calculation of compression resistance of reinforced stone elements is considered. It allows us to take into account the physical nonlinearity of deformation of materials of reinforced stone elements.
 
 Materials and methods. Accounting for physical nonlinearity is based on using deformation diagrams under “compression – tension”. Approximations of diagrams are given. A sample of experimental studies of the most characteristic armoured stone elements has been compiled according to the data of studies published in open sources.
 
 Results. The prerequisites for using a deformation approach to the calculation of reinforced stone elements are formulated. As a criterion for calculating the compression resistance at the ultimate strength stage, it is proposed to take the maximum force calculated from the condition of compatibility of deformations of masonry and longitudinal steel reinforcement. Algorithms for calculating the compression resistance and parameters of the stress-strain state of reinforced stone elements at any level of loading are compiled.
 
 Conclusions. The proposed calculation method makes it possible to obtain the parameters of the stress-strain state of elements of arbitrary cross-section shape with any reinforcement parameters and various eccentricities of longitudinal force application at all loading levels. A calculation criterion is proposed to take into account the redistribution of forces in the cross-section of armoured stone elements. Verification of the calculation method was performed on a sample of experimental data, which showed good convergence of theoretical and experimental values of load-bearing capacity and deformability.

CALCULATION OF OFFCENTRALLY COMPRESSED ELEMENTS

A large number of calculation formulas have been proposed to describe the deformation diagrams of masonry and concrete. The data indicate the possibility and expediency of using full masonry deformation diagrams to calculate the strength and deformations of stone and reinforced stone pillars. Experimental samples and stone pillars were tested. The samples were of five types and differed among themselves in the location of reinforcement and the reinforcement ratio, as well as in the method of loading – axial or off-center compression with different eccentricity. In the paper, experimental and calculated longitudinal deformations of masonry and reinforcement for samples of different groups. These data testify to the possibility and expediency of using full masonry deformation diagrams to calculate the strength and deformations of stone and reinforced stone pillars. As the amount of reinforcement in the stretched zone increases, most of the section works on the descending branch of the diagram. The size of the compressed zone increases, which is equivalent to a decrease in eccentricity. Reinforcement of the compressed zone with reinforcement increases the strength of sections with double reinforcement. The shapes of the stress profiles in the masonry practically do not depend on the presence of compressed reinforcement. The calculation establishes the expediency of the installation and the degree of saturation of the stretched and compressed cross-sectional areas with reinforcement. At small eccentricities, when the force is applied within the core of the section, saturation of the compressed zone with reinforcement leads to a noticeable increase in the strength of the section. At large eccentricities, saturation of the compressed zone with reinforcement is ineffective.

THE STRENGTH AND DEFORMABILITY OF THE LARGE-FORMAT POROUS CERAMIC BLOCKS MASONRY UNDER SHEAR

The article presents the results of experimental studies of shear strength, shear modulus and the limit value of the angle of shear deformations of masonry made of porous ceramic blocks with groove connection system of vertical joints. Studies of these parameters were carried out by the method of diagonal compression of masonry specimens, the vertical joints of which were made without filling and with filling with mortar. It is established that when filling vertical joints of masonry with a mortar on a mineral binding material, its shear strength and shear modulus significantly increase. It is indicated that it is necessary to take these factors into account when designing wall-stiffening diaphragms, multi-loaded load-bearing walls, floor-by-floor supported walls and partitions constructing using masonry from porous ceramic blocks.

A block-based variational elasto-damage model for masonry analysis inspired from granular micromechanics: Preliminary study

We develop a new block-based elasto-damage model for describing masonry structures. The constitutive elastic and damage behavioural laws used within the proposed approach are inspired from those employed in the recent literature in granular micromechanics. Adaptations have been made in many respects, notably the inclusion of impenetrability constraints through energy barriers. The analysis carried out in this paper proves that realistic masonry deformation modes can be obtained.

Pore Structure as a Determinant of Flexibility in Sustainable Lime-Cement Mortar Composites

Flexibility of Lime Mortar resulting from its good permeability feature through its relatively large interconnected pore structure makes it popular as an old sustainable building material. This characteristic feature enhances its capability to suppress masonry deformation. However, its mechanical strength is weak. To address this shortcoming, cement is added to form a stronger composite. This study, therefore, evaluates the pore structure of the resulting lime-cement composite, with a view to assessing impact and sustainability of the lime’s flexibility in the overall performance of the composite. Adopting equal mix ratio (1:3) of Binder/Aggregate (B/A), mortars were prepared using lime as a lone binder, as well as other five different compositions in the ascending and descending order of lime and cement binders (i.e., 1:1, 1:2, 1:3, 2:1 and 3:1). Each composition was assessed in fresh state using Water/Binder ratio, Air Content and Bulk Density. For the hardened state assessments, mechanical characteristics and microstructural features evaluated through six (6) and twelve (12) month curing periods respectively, were considered. Results of the investigation reveal that low cumulative porosity (i.e., summation of the porosities) across the three pore regions of Inter-Nano pores (1 – 10 nm), Super-Nano pores (10 – 100 nm) and Sub-Micro pores (0.1 – 1 µm), for each of the mortars, is observed to be synonymous with low cement content, low Modulus of Elasticity, low (fc/ff), and thus, high flexibility. This observation is supported by high linear coefficient of correlation (R2 = 0.89) for the equation describing both ‘cumulative porosity’ (within the referenced three pore ranges) and cement content. Thus, it could be inferred that despite cement addition with resulting alteration in the pore structure of the composite, presence of lime would retain flexibility property of the composites, with more flexibility in the descending order of cement contents. Considering the impacts of pandemic climate change, growing energy costs and human activities on the environment, this study therefore attempts to promote revival of an old but partially abandoned sustainable lime based mortars, with a view to facilitating improved lime mortar performances, conservation of energy resources and overall protection of the environment.

Pore Structure as a Determinant of Flexibility in Sustainable Lime-Cement Mortar Composites

Flexibility of Lime Mortar resulting from its good permeability feature through its relatively large interconnected pore structure makes it popular as an old sustainable building material. This characteristic feature enhances its capability to suppress masonry deformation. However, its mechanical strength is weak. To address this shortcoming, cement is added to form a stronger composite. This study, therefore, evaluates the pore structure of the resulting lime-cement composite, with a view to assessing impact and sustainability of the lime’s flexibility in the overall performance of the composite. Adopting equal mix ratio (1:3) of Binder/Aggregate (B/A), mortars were prepared using lime as a lone binder, as well as other five different compositions in the ascending and descending order of lime and cement binders (i.e., 1:1, 1:2, 1:3, 2:1 and 3:1). Each composition was assessed in fresh state using Water/Binder ratio, Air Content and Bulk Density. For the hardened state assessments, mechanical characteristics and microstructural features evaluated through six (6) and twelve (12) month curing periods respectively, were considered. Results of the investigation reveal that low cumulative porosity (i.e., summation of the porosities) across the three pore regions of Inter-Nano pores (1 – 10 nm), Super-Nano pores (10 – 100 nm) and Sub-Micro pores (0.1 – 1 µm), for each of the mortars, is observed to be synonymous with low cement content, low Modulus of Elasticity, low (fc/ff), and thus, high flexibility. This observation is supported by high linear coefficient of correlation (R2 = 0.89) for the equation describing both ‘cumulative porosity’ (within the referenced three pore ranges) and cement content. Thus, it could be inferred that despite cement addition with resulting alteration in the pore structure of the composite, presence of lime would retain flexibility property of the composites, with more flexibility in the descending order of cement contents. Considering the impacts of pandemic climate change, growing energy costs and human activities on the environment, this study therefore attempts to promote revival of an old but partially abandoned sustainable lime based mortars, with a view to facilitating improved lime mortar performances, conservation of energy resources and overall protection of the environment.

Features of deformation and destruction of fine-grained fiber concrete

The article analyzes the conditions of buildings construction in town Shakhty after the closure of coal mining enterprises. The appearance of deformation processes after old mine workings were flooded, is usually accompanied by uneven surface deformations and cracks formation in load-bearing structures is noted in the article. The positive effect of polypropylene microfiber additives on the deformation properties of Portland cement masonry solutions was studied, as it significantly reduces the probability of cracks in building structures. The results of experimental studies of mechanical properties of compositions with optimal dosage of polypropylene microfiber are presented. An increase in flexural and compressive strength of microfiber-modified samples was noted in comparison with the control ones. The dependence of ultimate deformations on normal stresses is established, which allows predicting the permissible ultimate deformations of masonry. The module of the total solution strain was evaluated.

Influence of temperature-humidity deformations of masonry on crack resistance of wall filling in the frame buildings

В статье проанализированы возможные причины появления дефектов в штукатурном слое после ремонта здания исторической застройки. Проведены комплексные исследования, включающие анализ составов, технологию нанесения и условия твердения и эксплуатации. Предложены штукатурные составы, основанные на аутентичных, с модификацией полимерными грунтами

Influence of temperature-humidity deformations of masonry on crack resistance of wall filling in the frame buildings

в зависимости от способа их сопряжения с железобетонным монолитным каркасом. Установлены предельные значения длины стен в зависимости от способа опирания каменной кладки и вида кладочных изделий. Показано, что усадка каменной кладки вызывает в стене появление главных растягивающих напряжений, траектории которых совпадают с направлением горизонтальных растворных швов. При этом в стенах с оконными проемами наиболее подверженной трещинообразованию является подоконная область кладки. Приведены зависимости, связывающие жесткость узлов сопряжения стены с вертикальными элементами каркаса с величиной главных растягивающих напряжений, возникающих в стене при нормируемых значениях усадочных деформаций каменной кладки. Предложены конструктивные мероприятия, позволяющие снизить риск образования трещин в стенах каркасных зданий. Данные мероприятия включают устройство разделительного слоя между каменной кладкой и плитой перекрытия, применение податливых связей в узлах сопряжения стенового заполнения с каркасом, а также армирование горизонтальных швов каменной кладки или устройство деформационных швов.

Deformability And Seismic Resistance Of Masonry Constructions

The article presents the results studies of elastic-plastic deformation masonry under biaxial stress state. The results of experimental research masonry deformation in conditions corresponding to the mode of operation under seismic influences are presented. Shows the mechanisms of formation and accumulation of micro destruction in a biaxial stress state. The presence the plastic phase of deformation masonry in the conditions of seismic influences is proved. Based on the research results, the values of the masonry ductility coefficients for biaxial stress state conditions and the values of the allowable damage coefficients for stone structures of earthquake-resistant buildings were determined. The research results confirm the correctness of regulatory approaches to the calculation masonry structures earthquake-resistant buildings, taking into account the allowable amount of damage.

Whether Can Wall Masonry of Ceramic Hollow Stone Has Plasticity

The results of domestic and foreign experimental studies of masonry made of large-format ceramic hollow bricks and stones with voidness of up to 54% on the effect of static load during compression are analyzed. They confirmed the conclusions made by Russian scientists in the 1950s-1960s when developing the theory of stone masonry. Based on the analysis of the nature of deformation of the masonry of the large stone and the use of modern approaches to the assessment of the process of crack formation and failure of masonry the possibility of her plastic deformations is assessed. It is shown that the masonry of ceramic large-format stone refers to brittle materials. Based on the analysis of the test results, it is noted that according to the theory of plastic media, there is the simplest model of destruction of masonry during loading, in which plastic deformation can occur in the local zones of the element (crack zones). In this case, the bulk of the body (sample) is in an elastic state. The fallacy of the proposed approach to the estimation of the coefficient of plasticity of masonry, with due regard for the ratio of elastic and total deformations of masonry is noted. It is established that the proposals of individual authors to assess the plasticity of the wall masonry of ceramic brick and large-format ceramic stone with voidness of more than 40 % are incorrect and does not meet the work of the masonry of hollow material. On the basis of a large number of research works, it is concluded that the appearance and development of cracks and damage in the masonry is associated with the effects of its brittle destruction, and the masonry of large-format hollow stone refers to brittle materials.

ДЕФОРМАЦИИ РАСТВОРА ГОРИЗОНТАЛЬНЫХ ШВОВ КАМЕННОЙ КЛАДКИ ПРИ СЖАТИИ

The necessity of establishing and determining the consistency of mortars deformation in the horizontal joints of masonry is established: in the absence and development of cracks and with the exhaustion of resistance ranging from 80 – 85 % of the total deformation of masonry under short-term compression. Attention is paid to the absence of reports in the scientific literature on the conduct and results of research on the spatial stress-deformative state of the mortar in the joints of masonry under compression. The advantages of studying the secant modulus of deformation Ep are emphasized in solving various issues in the theory of operation and method for calculating the masonry. On the basis of long-term research results, the essential difference between the change in the secant modulus of cement mortars deformation E'p of varying strength of horizontal joints from the nature of its change when tested in standard samples is shown analytically and graphically. The advantages of the developed methodology for processing the results of investigations of mortars in standard samples are noted. It allows to more accurately set the actual values of normal strain modulus E0 and the ultimate relative deformation under compression. The analytical dependences of the plasticity coefficient and the secant modulus of deformations E'p are found based on processing the results of numerous studies of masonry mortars

The Influence of Compressive Stress on the Load-Bearing Capacity of Masonry Subjected to Vertical Displacements

The paper describes the results of tests of masonry wallets made of solid clay bricks with joints of normal thickness (10 specimens) and filled vertical joints and autoclaved aerated concrete (AAC) blocks with thin joints and unfilled vertical joints (5 specimens). The specimens made of clay bricks were 1290 mm wide, 1415 mm high and 250 mm thick, while the specimens made of AAC blocks had the width of 1250 mm, the height of 1510 mm and the thickness of 240 mm. The tests were carried out in a specially designed steel test stand witch which the masonry specimens were monolithised. The force applied along the vertical edge of the specimens and causing the vertical displacements was carried out by means of hydraulic cylinder. The masonry specimens were tested without participation of vertical compressive stresses perpendicular to the bed joints σc or the tests were carried out after initial compression, which induced stress in the wall with mean values from 0.3 to 1.5 N/mm2 for solid clay brick specimens and 0.9 N/mm2 in walls made of AAC blocks. The compressive loads were implemented using four pairs of tensioned steel tendons equipped with springs to compensate the influence of masonry displacements. The deformation angles of masonry were also investigated. Deformation angles were calculated based on changes in the length of the system of measuring bases placed on both surfaces of the specimens. The compressive stresses σc influenced the values of the mean shear stress τcr,σ (force inducing vertical displacements divided by the area of the vertical cross-section of the specimen) at which the first oblique crack appeared. The τcr,σ stress was always greater than the stress τcr,0 at which the first crack occurred in the specimens tested without compression. The ratio τcr,σ/τcr,0 for solid clay brick specimens ranged from 1.38 to 2.24, depending on the stress value σc and 2.18 for masonry made of AAC blocks. Compressive stresses also influenced the increase of the masonry deformation angles at the moment of the first cracking θcr,σ in relation to the deformation angle θcr,0 of the specimens tested without compression. This effect was proportional to the increase of τcr so that the mean modulus of deformation was about 1630 N/mm2 for clay brick walls. In the case of specimens made of AAC blocks a ratio of stress to angles of deformation Gcr equal to 631 N/mm2 when the tests were not accompanied by compressive stresses (σc = 0) and 461 N/mm2 when σc = 0,90 N/mm2. Similar results were obtained in the case of the effect of the compressive stress σc on the increase of shear stress τu and the accompanying deformation angles λu at the maximum force inducing vertical displacements of masonry specimens obtained in tests.

Investigation of the Behavior of Hardening Masonry Exposed to Variable Stresses.

This paper analyzes the behavior of masonry under variable loads during execution (construction stage). It specifies the creep coefficient for calcium silicate brick masonry, presenting the research data of masonry deformation under variable and constant long-term loads. The interaction of separate layers of composite material in masonry is introduced and the formulae for determining long-term deformations are offered. The research results of masonry’s compressive strength and deformation properties under variable and constant long-term loads are presented. These are then compared to calculated ones. According to the presented comparison, the calculated long-term deformations coincide quite well with those determined experimentally.

APPLICATION of ARAMIS SYSTEM FOR MEASUREMENT OF DEFORMATIONS OF MASONRY

The paper presents the results of measurements of displacements and strains obtained on fragments of walls made of bricks. In addition to the Instron measurements, the displacements were measured on the specimen surface by using the modern non-contact measuring system ARAMIS, which has a direct interface with the strength testing machine and determines displacements by means of two cameras. The results were used to determine the average strain and the observation of the propagation of cracs in masonry panel.

ANALYSIS OF STRESS-STRAIN STATE OF REINFORCED CONCRETE PLATE AROUND SUPPORT ZONES

Structural analysis of the formation and evolution processes of structural microdestruction with the tran-sition to macrorestriction occurring during plastic deformation of masonry under biaxial stresses. The dependencies that determine the amount of the plastic phase of the deformation of masonry. Identified processes and their corre-sponding strength criteria, which play a key role in the implementation phase of plastic deformation. It is shown that plastic deformation of masonry under biaxial stresses occurs when the physical line operation of the basic ma-terials of masonry (brick and mortar). Found that the plastic properties of masonry under biaxial stresses are deter-mined by the processes occurring at the nodes of contact interaction of brick and mortar in horizontal and vertical joints. According to the results of numerical studies the values of the coefficients of ductility of masonry at different variants of mechanical characteristics of brick, mortar and adhesive strength of their interaction.

Study of the compressive response of masonry using non-conventional joint materials

The compressive response of masonry is influenced by geometric, material and execution variables. In addition, the nature of bricks and mortar typically introduces uncertainty to the experimental results. In order to reduce this uncertainty, an experimental campaign has been carried out to analyse the influence of the properties of the joints. Four non-conventional masonry typologies including resin, EPS and rubber joints have been considered for this purpose. In all, 60 compressive tests and 50 deformability tests on five stacked bricks prisms were performed. Obtained data are compared with data from the literature. A comparison with the current European standard is also carried out. The obtained results point out that the modulus of linear deformation of the joint is the most influent variable on the compressive response of masonry. Finally, it seems that current formulation (Eurocode-6) tends to overestimate the modulus of linear deformation of masonry.

Study of the compressive response of masonry using non-conventional joint materials

The compressive response of masonry is influenced by geometric, material and execution variables. In addition, the nature of bricks and mortar typically introduces uncertainty to the experimental results. In order to reduce this uncertainty, an experimental campaign has been carried out to analyse the influence of the properties of the joints. Four non-conventional masonry typologies including resin, EPS and rubber joints have been considered for this purpose. In all, 60 compressive tests and 50 deformability tests on five stacked bricks prisms were performed. Obtained data are compared with data from the literature. A comparison with the current European standard is also carried out. The obtained results point out that the modulus of linear deformation of the joint is the most influent variable on the compressive response of masonry. Finally, it seems that current formulation (Eurocode-6) tends to overestimate the modulus of linear deformation of masonry.