Dissertations / Theses on the topic 'Load strength of brick masonry'

A significant number of buildings are supported by load-bearing masonry walls. The preservation of these worldwide used structures is a sustainable alternative. However, there is little research about the structural response of these particular elements if compared with others like concrete or steels framed structures. Hence, a further study of the load-bearing masonry walls is necessary as a starting point for the preservation activities. The load-bearing masonry walls are usually subjected to a vertical eccentric loading condition, which is related with their complex structural response. This response is characterised by the second-order bending effects due to the eccentricity of the load, the non-linear compressive response of the masonry and its almost negligible tensile strength. Thus, strengthening these walls, in order to increase their load-bearing capacity, is an interesting upgrading alternative to enhance their life-cycle. In this thesis, an experimental campaign has been carried out. It consisted of hundreds of characterisation tests to obtain the mechanical properties of the component materials which have been used to build twenty-nine full-scale walls. Twenty of these walls were unreinforced and the other nine were TRM (Textile Reinforced Mortar) strengthened. All of them have been tested under eccentric compressive loading conditions. The analysis of the strengthened walls has allowed studying the influence of the strengthening mortar type on the load-bearing capacity. The effects using anchors or embedding different types of fibre grids have been also analysed. A bidimensional (2D) simplified micro-model has been implemented to analyse these structural cases. This numerical tool has been validated using the data from the experimental campaign. Finally, analytical methodologies have been proposed to calculate the load-bearing capacity of unreinforced and TRM-strengthened brick masonry walls. Similarly, two current standards, Eurocode-6 and ACI-530 have been applied to the analysed cases and their results have been compared with the experimental ones. The results show that the TRM provides a load-bearing capacity increase over 100% and homogenises the structural response, which becomes stiffer. Regarding the simulations, the proposed numerical model provides accurate results, which are better for the cases with larger slenderness or larger eccentricity of the applied load. Finally, the proposed analytical methods provide acceptable results, which are more accurate than the ones obtained by applying the formulations included in the analysed standards.
Un nombre significant d'edificis estan suportats per murs de càrrega d'obra de fàbrica. La preservació d’aquestes estructures que s’utilitzen arreu del món is una alternativa sostenible. No obstant això, hi ha molt poca recerca en relació a la resposta estructural d’aquests elements particulars si es compara amb altres com les estructures porticades d’acer o formigó. Per tant, és necessari un major estudi dels murs de càrrega d’obra de fàbrica com a punt de partida de les actuacions de preservació. Normalment, els murs de càrrega estan subjectes a patrons de càrrega vertical excèntrica, cosa que està relacionada amb la seva resposta estructural complexa. Aquesta resposta es caracteritza pels efectes de flexió de segon ordre degut a l’excentricitat de la càrrega, per la resposta no linear a compressió de l’obra de fàbrica i per la seva, pràcticament negligible, resistència a tracció. Per tant, el reforç d’aquests murs, per tal d’augmentar-ne la seva capacitat resistent is una alternativa de millora interessant per allargar la seva vida útil. En aquesta tesi s’ha dut a terme una campanya experimental. Aquesta ha consistit en centenars d’assaigs de caracterització de les propietats mecàniques dels materials components utilitzats per construir vint-i-nou murs. Nou d’aquests es van reforçar amb Textile Reinforced Mortar, TRM, i els altres vint van ser assajats sense reforç. Tots van ser sotmesos a compressió excèntrica. L’estudi dels murs reforçats ha permès analitzar la influència del tipus de morter de reforç, l’efecte de disposar ancoratges o la dependència de la capacitat resistent en el tipus de malla de fibra utilitzada. S’ha implementat un micromodel simplificat bidimensional (2D) per analitzar els casos estructurals proposats. Aquesta eina numèrica ha estat validada utilitzant les dades de la campanya experimental. Finalment, s’han proposat mètodes analítics per calcular la capacitat portant dels murs sense reforç i dels reforçats amb TRM. De forma semblant, s’han aplicat dos normes actuals, l’Eurocodi-6 i l’ACI-530, als casos d’estudi per tal de comparar-ne els resultats amb els experimentals. Els resultats mostren que el TRM aporta un augment de la capacitat resistent de més del 100% i homogeneïtza la resposta estructural que esdevé més rígida. En relació a les simulacions, el model numèric proposat obté resultats acurats, els quals són millors pels casos de major esveltesa o més excentricitat de la càrrega. Per acabar, els mètodes analítics que es proposen aporten resultats acceptables, els quals s’ajusten millor als experimentals que els obtinguts aplicant les formulacions de les normatives.

Despite their poor performance, non-standard clay bricks are commonly used in construction of low-rise buildings and rural houses in Indonesia. These clay bricks are produced traditionally in home industries. Indonesia is located in an active seismic region and many masonry buildings were badly damaged or collapsed during recent earthquakes. Such buildings are classified as non-engineered structures as they are built without using any proper design standard. Lateral load response of un-reinforced masonry walls is investigated in this research project, with the aim of better understanding the behaviour of these masonry walls using low quality local bricks. A comprehensive experimental program was undertaken with masonry wall elements of 600 mm x 600 mm x 110 mm constructed from local bricks from Cikarang in West Java - Indonesia. Wall specimens were constructed and tested under a combination of constant vertical compression load and increasing horizontal or lateral in-plane loads, of monotonic, repeated and cyclical nature. The vertical compressive loading was limited to 4% of maximum brick compressive strength. Masonry mortar mix used to construct the specimens was prepared according to Indonesian National Standard. Three different types of masonry wall panels were considered, (i) (normal) brick masonry walls, (ii) surface mortared brick masonry walls and (iii) comforted surface mortared brick masonry walls. The results indicated that the lateral load bearing capacity of masonry wall is usually lower than that of mortared and comforted walls. Despite this, the lateral load capacity under cyclic loads decreased 50 % of the average capacity of the walls under monotonic and repeated lateral loads. Using the results from the experimental program, a simplified model for the equivalent diagonal spring stiffness of local clay brick walls was developed. This stiffness model derived from experimental results in then used to simplify the structural analysis of clay brick wall panels in Indonesia. The design guideline for brick masonry houses and low-rise buildings in six Indonesian seismic zones was developed, as a contribution towards the development of design guidance for constructing brick masonry houses in Indonesia.

The primary objective of this research program was to investigate the effective modulus of elasticity and shear modulus of brick masonry walls under lateral load, and to to justify using the Jaeger and Mufti method to calculate the effective modulus of elasticity and shear modulus of brick masonry walls. The experimental program involved the testing of three unreinforced brick masonry walls under in-plane and vertical loads. Linear Variable Differential Transducers were used to record the horizontal and vertical displacements of the walls. The experimental results were used to evaluate the modulus of elasticity and the shear modulus of walls under flexure. The experimental results were compared to the finite element analysis results. It was found that the finite element analysis yields similar results to the experimental results. It was also found that the Jaeger and Mufti method to calculate effective modulus of elasticity and shear modulus of brick masonry walls is effective for design purposes.

Genom historien har flera olika tegelkonstruktioner använts. På 50-talet utvecklades skalmuren som idag dominerar tegelmarknaden. En studie har utförts i ett försök att förbättra hur skalmurar ska dimensioneras. Kommersiella beräkningsmodeller som används i dagsläget resulterar i överdimensionerade skalmurar där dyra konsoler möjligtvis används i onödan. Skalmurar utsätts i princip endast för sin egentyngd och är därför huvudlasten vid dimensionering. Syftet med rapporten är att utveckla en mer korrekt metod för uträkning av egenviktens fördelning i skalmurar för att minska belastningen i murverkets svaga områden. Detta kan i sin tur göra det möjligt att konsoler inte behöver användas för att förstärka de svaga delarna. Arbetet utforskar möjligheten att använda finita elementmetoden för att beräkna egentyngdens fördelning och utförs med programmet FEM-design. De nuvarande kommersiella beräkningsmodellerna använder sig inte av finita elementmetoden och skillnaderna mellan dessa två olika utgångslägen är okända. Rapportens huvudmål är att jämföra den nya metoden som tillämpar finita element metods beräkningar gentemot den gamla metodens beräkningar. Detta utförs genom att studera ett fiktivt exempel av en skalmur som med den gamla metoden hade behövt konsoler. Resultatet visade att den nya metoden kan förbättra egentyngdens fördelning i skalmuren och konsoler kan därför undvikas i detta fall.
Throughout Sweden’s history several distinct types of masonry constructions have been used. In the late 1950s the most common masonry construction that dominates today’s market was developed. A study has been conducted in an attempt to better understand how masonry constructions are to be designed. Commercial calculation methods applied for sizing cavity walls today results in oversized constructions that are reinforced with expensive consoles. The consoles are placed in the cavity wall for supporting the masonry were it would otherwise break. A new calculation method could prove these consoles to be an unnecessary expense. A cavity wall is by principal only exposed by its own dead-load and is therefor the main load when sizing the wall. The purpose of this study is to develop a more accurate method of calculating the spread of the deadload in the cavity walls masonry. This could prove that the weaker points in the wall is not in need of reinforcement by consoles. This study will investigate the possibility to use the finite element method for the calculation of the deadloads spread inside a cavity wall. Commercial calculation methods that are used today does not use the finite element method and the differences in these two initial states are unknown.

This research work proposes methods to rises the resistance and to evaluate the behavior of confined masonry walls built from clay solid bricks. These elements are widely used in Guerrero State (México) to build masonry structures, which should resist high lateral loads because of the serious seismic hazard. Therefore, a large experimental program to evaluate the mechanical properties of bricks and masonry currently required in the design process and masonry analysis was developed. To rises the masonry resistance and to counteract the influence of the compressive strength of the pieces on the masonry behavior, a high compressive strength mortar and a metallic reinforcement inside the joints were used. With respect to referenced values of the mechanical properties, some were similar and others were twice bigger. In this country zone, the first three tests under lateral load on full-scale confined masonry walls built from clay solid bricks were carried out in order to evaluate its behavior. A reinforcement composed by metallic hexagonal mesh-mortar coat was placed on the faces of two walls to rise or to restore the resistance. The walls showed good behavior and the reinforcement had adequate structural efficiency. Numerical models of panels and walls built by using the experimental data evaluated the envelope resistance, the failure mode and showed the influence of the mechanical properties of the pieces and joints on the global behavior. Two models had metallic reinforcement inside the joints. In addition, a constitutive law of the masonry defined from experimental results allowed to elaborate a simple model, which results were concordant with respect to the experimental results and similar to those calculated by complex models. Finally, two simplified models to evaluate the resistance of confined masonry walls by considering the failure plane on the wall diagonal were developed. One supposes the masonry failure by shear effect and the other supposes the masonry failure by induced tension. The ratio theoretical resistance vs. experimental resistance was adequate for walls built from different materials and tested under different loads, which had ratio Height/Length ranging from 0.74 to 1.26

This diploma thesis deals with the diagnostics of masonry structures. In the theoretical part of this thesis it is described the system of assessment of existing structures and then the assessment of existing masonry structures. The next chapter states the methods of survey of masonry structures, including evaluation. The practical part of the thesis deals with the survey of the building of a small castle. This survey includes a brief history of the castle building, the preliminary inspection of the building and the research of the supporting structure. The result of the survey is to determine the material characteristics of masonry.

The subject of this diploma thesis is the diagnostic survey of the masonry walls and the connecting bridge in the East Moat of Špilberk Castle. The thesis contains theoretical information about survey and diagnostics of building construction and then evaluation of diagnostic methods used for estimation of essential characteristics of masonry structures. In the practical part the diagnostic investigation of Špilberk Castle walls is processed. That includes determination of material characteristics of the studied structure. In the conclusion there is a suggestion of how to eliminate the structural defects found during the survey.

The determination of strain properties of masonry in the direction parallel to bed joints is a fundamental pre-requisite for designing structures, where masonry is subjected to horizontal stresses (e. g. strengthening with prestressing). The diploma thesis summarized techniques of determination of masonry modulus of elasticity presented in available literature. The goal is to suggest suitable methodology of determination of masonry modulus in direction parallel to the bed joints. In the practical part of the diploma thesis is that methodology verified by experimental test and results of tests are analyzed and discussed.

The subject of this thesis is the diagnostic investigation of block A in the object at Rumiště 8, Brno. The work includes theoretical knowledge of technical surveys and diagnostic methods and their evaluation to identify the essential characteristics of masonry and timber structures. In the practical part is the diagnostic investigation processed. Part of the diagnostic investigation is the determination of material characteristics of the structure. At the end of the thesis is an assessment of the structure.

The aim of my master’s thesis is to develop a brief overview of the historical development of brick, diagnosis methodologies of masonry structures and their application in the practical part for evaluation of structural survey masonry, carried out at the Faculty of Philosophy, Masaryk University in Brno.

Masters Research - Master of Philospohy (MPhil)
It has been shown that masonry material properties, in particular, unit flexural bond strength (ft), vary significantly throughout masonry structures, despite the fact that often only one type of brick and mortar are used. Unit flexural bond strength was previously identified as one of the most important material parameters contributing to the strength of clay brick unreinforced masonry (URM) walls in flexure. It was the objectives of this research, in the context of clay brick URM walls subject to vertical bending, to examine how unit flexural bond strength varied spatially in a clay brick URM wall, determine a best fit probability distribution function which can describe expected variability in unit flexural bond strength and determine how this variability and other factors affect wall behaviour and failure load using 3D non-linear finite element analysis (FEA). It was hoped that modelling a full sized clay brick URM wall subject to vertical bending using a 3D non-linear FEA model would more accurately predict wall failure load (compared to current analytical methods) and allow the examination of crack pattern development as the wall progresses to failure upon being laterally loaded. The first part of the research project was to conduct an experimental program to examine unit-to-unit spatial strength correlation within six full sized clay brick URM walls and to characterise a unit flexural bond strength probability distribution. It was observed that although weak correlation in unit flexural bond strength exists in some courses and between courses, these locations were difficult to predict and didn����t follow any particular pattern relating to for example, mortar batch. Therefore, although somewhat counter-intuitive, the results indicate that statistically significant correlation between adjacent unit flexural bond strengths is not likely to be observed. It was also observed that clay brick wall unit flexural bond strengths obtained for all of the walls tested best fit a truncated Normal probability distribution. Strength of the brick/mortar interface appeared to be governed by factors relating to workmanship (and therefore mortar quality and moisture content), weather (which can affect material characteristics like brick suction rate) and inherent material variability. It would appear that brick suction rate can significantly affect the overall strength of a URM wall. v Stochastic analysis was conducted for walls with and without uncorrelated spatial variability in unit flexural bond strength and associated tensile fracture energy (GfI ). It was found that the TNO DIANA 9.2 FEA package could be used to implement spatial variability of various material parameters and reasonably accurately model failure of clay brick URM walls in vertical bending. From the non-linear FEA model development stage, it was observed that because the brick/mortar bond has significantly more strength capacity in compression, it appears that the lateral load resistance of the wall comes from a combination of the ability of the brick/mortar bond to tensile soften while providing significant compressive resistance at the compressive edge. It was found for a spatial stochastic analysis with spatial variability in bond strength (referred to from now on as a spatial stochastic analysis), with COVs of 0.1, 0.3 and 0.5, that COV of wall failure loads were relatively small, being 0.02, 0.04 and 0.06 respectively. For the non-spatially varying stochastic analysis with fully correlated bond strength (now referred to as non-spatial stochastic analysis), with COVs of 0.1, 0.3 and 0.5, COV of wall failure loads were 0.07, 0.20 and 0.32 respectively. For the spatial stochastic analysis, it was found that with a bond strength COV increase from 0.1 to 0.5 the mean wall failure load dropped from 2.25 kPa to 2.0 kPa (an 11% reduction). Despite the relatively small drop in magnitude of the mean wall failure load with increase in bond strength COV, the mean wall failure loads were statistically different to one another. For the non-spatial stochastic analysis, mean failure load stayed relatively constant at 2.24-2.25 kPa. These results could be explained by examining the 3D wall progression to failure. For walls with spatial variability in bond strength, it is expected that wall failure load COVs would be smaller because those walls would consistently be composed of smaller valued bond strengths which would consistently contribute to weakness in the wall. For the non-spatial wall simulations, this effect would not occur as failure load is determined by one uniform weak or strong bond strength. It was proposed that failure of a clay brick URM wall is not governed by one course only cracking, but rather, instability in the wall is governed by several courses in the vicinity of locations of large bending moment. It was shown that various current stochastic approximations which employ a unit failure hypotheses in combination with a linear/elastic approximation for first cracking load all underestimated wall capacity significantly. The reason for this is suggested as being vi because all hypotheses only assume failure is governed by one course and linear/elastic theory only considers the tensile capacity of a joint and neglects strength capacity available as a result of joint tension softening and the resistance to failure provided by compressive strength on the compression side of the wall. The hypotheses also don’t take into consideration factors which affect overall wall bond strength mean which result from influences such as workmanship, weather and material variability factors, such as (for example), variation in brick suction rate due to weather conditions which can make the overall strength of the wall stronger or weaker. Based upon a comparison in wall failure load COV for the spatial and non-spatial stochastic wall analysis results, a more realistic approach for future modelling attempts of spatial variability in masonry material properties is suggested. This would address the issue of external factors such as workmanship and weather on the overall strength of the wall, as well as the inherent bond strength variability due to material variability. For walls with spatial variability in bond strength, upon examination of numerous wall simulation results, several crack patterns were witnessed and are discussed.

碩士
國立成功大學
建築學系碩博士班
91
In Taiwan, most historical buildings are laid with bricks. These brick masonry may cause damage easily as result of weak ductility, environmental changes, and degradation of construction materials. Therefore, when historical buildings are repaired and reused, it is necessary to strengthen their structure. The CFRP has called attention to repairing historical buildings, due to its lightweight, high tensile strength and easy working. More important, the bond strength between the CFRP and brick masonry is the key of effects. In this study two kinds of bricks, five kinds of mortar and eight kinds of brick walls will be tested through three experiments, including:(Ⅰ) the bond strength between the CFRP and a single substrate, (Ⅱ) the bond strength between the CFRP and brick walls, and (Ⅲ) the bond strength between the CFRP and a single substrate after accelerated aging test. The conclusion, Experiment (Ⅰ) appears that the main affecting factors are types of bricks and mortar and with or without primers. Smooth surfaces of new bricks are disadvantaged to bonding with the CFRP and bricks. The bond strength of mortar directly relates with contents of cement. Plus, using primer can generally enhance the bond strength. Experiment (Ⅱ) shows that the bond strength between the CFRP and old brick walls would be greater than new brick walls. The order of affecting factors is listed as follows: (1) the kinds of bricks, (2) with or without primers, (3) the kinds of mortar. Experiment (Ⅲ) occurs that the bond strength between the CFRP and old bricks and the bond strength between the CFRP and mortar would not decrease significantly under short-term ultraviolet and moisture.