No description available.

Wide spaced reinforced masonry (WSRM) walls that contain vertical reinforced cores at horizontal spacing up to 2000mm are commonly used in high wind zones of Australia although their inplane shear resistance is not well understood. This thesis aims at providing better insight into the behaviour of WSRM walls subjected to inplane lateral loading through experimental and numerical investigations. The interactions between the unreinforced masonry (URM) panels and vertical reinforced cores are first determined using an elastic finite element analysis and the potential failure paths hypothesized. The hypotheses are then validated using a series of full-scale WSRM and Non-WSRM wall tests under monotonic and cyclic lateral loading by keeping the spacing between the vertical reinforced cores as the main design variable. Load-displacement response of these shear walls indicates that the current classification of the WSRM in AS3700 (2001) as those walls containing vertical reinforced grouted cores at 2000mm maximum spacing is appropriate. A finite element model (FEM) based on an explicit solution algorithm is developed for predicting the response of the masonry shear walls tested under static loading. The FEM has adopted macroscopic masonry failure criteria and flow rules, damaged plasticity model for grout and tension-only model for reinforcing bars reported in the literature, and predicted crack opening and post-peak load behaviour of the shear walls. By minimising the kinetic energy using appropriate time scaling, the FEM has provided reasonable and efficient prediction of load flow, crack patterns and load–displacement curves of the shear walls. The FEM is further validated using full-scale tests on WSRM walls of aspect ratios and pre-compression different to that tested before. The validated FEM is used to examine the appropriateness of the prescriptive design details for WSRM concrete masonry shear walls provided in AS3700 (2001) allowing for a large scatter in material properties. It is shown that the inplane shear capacity formula provided in AS3700 (2001) for squat WSRM shear walls is non-conservative.

No description available.

No description available.

L’objectif principal de cette étude est de développer des outils de simulation numérique pour évaluer la vulnérabilité des constructions en maçonnerie sous chargements variés. Ainsi, le comportement de la maçonnerie non armée sous chargement monotone en macro- et micro-échelles est étudié. La simulation du comportement non linéaire du mur de maçonnerie avant et après le pic et la capture de son mécanisme de rupture sont les points centraux de ce travail. Tout d'abord, le mur de maçonnerie d’un panneau est remplacé par deux barres simples utilisant la stratégie des macros-éléments et un comportement tri-linéaire est proposé pour évaluer la résistance à la rupture de la paroi ainsi que son comportement avant et après le pic. L'absence de l'information sur le mécanisme de rupture du mur de maçonnerie et la relation entre le mécanisme de rupture et les propriétés mécaniques des éléments barres dans ce type de modélisation conduisent à opter pour une autre description de ces structures à savoir la stratégie de micro-modélisation. Dans cette stratégie, les unités et les mortiers sont modélisés séparément et l’ensemble du comportement inélastique du mur de maçonnerie est supposé se produire dans les mortiers. Par conséquent, une attention particulière sera accordée au développement d'une description fiable des propriétés matérielles de ces éléments à l'aide d'une loi constitutive précise. La représentation tridimensionnelle d'un mur de maçonnerie faite dans ce travail, améliore la capacité des méthodes actuelles pour prédire le comportement de la maçonnerie sous les deux chargements en plan et hors du plan. D’abord, des enveloppes de rupture comprenant la tension limite et la surface de charge de Mohr-Coulomb sont assignées à l'élément d'interface du code éléments finis GEFDyn. Ensuite, la loi de comportement est améliorée en ajoutant un seuil de compression aux surfaces de charge pour inclure l’endommagement en compression de la maçonnerie à travers l'élément d'interface. Dans le nouveau modèle élastoplastique, les écrouissages négatifs des seuils de traction et de compression ainsi que la cohésion du mortier sont pris en considération. La capacité des deux modèles pour reproduire le comportement avant et après le pic de la résistance au cisaillement du mur de maçonnerie est vérifiée en comparant les résultats numériques avec les données expérimentales. L'importance de l’interaction entre les seuils de compression et celui du cisaillement est montrée en comparant les résultats obtenus avec ceux d'un test réel. Les résultats ont révélé que le second modèle est capable de simuler le comportement du mur de maçonnerie avec une bonne précision. Ensuite, l'effet des propriétés géométriques de la paroi telles que l’existence d’une ouverture et l'élancement, les propriétés des mortiers comme la cohésion, la résistance en traction et la résistance en compression ainsi que la contrainte verticale initiale dans le mur, sur la résistance latérale et le mécanisme de rupture des murs de maçonnerie est démontré. En outre, afin de présenter l’état d’endommagement, des indices de dommage, portant sur la longueur totale des fissures dans différentes rangées et colonnes de mortiers sont introduits et comparés pour différentes configurations. Les longueurs de glissement et d’ouverture de fissures dans les mortiers horizontale et verticale respectivement, sont les paramètres les plus importants qui contrôlent le comportement du mur. Enfin, la relation entre les profils de fissuration différents et les propriétés des matériaux y contribuant sont résumées dans un tableau. / The aim of this thesis is to develop numerical models for evaluating the vulnerability of unreinforced masonry construction under different types of loading. Therefore, the behavior of unreinforced masonry panels under monotonic loading in both macro- and micro- scales is studied. Simulating the nonlinear behavior of the masonry wall in pre and post-peak regions and capturing its failure mechanism is the main focus of this study. First, the masonry wall in the panel is substituted by two simple bars using the so-called macro-element strategy and a tri-linear behavior is proposed to assess the ultimate strength of the wall as well as its response before and after peak. The lack of information about the failure mechanism of the masonry wall and relation between the failure mechanism and mechanical properties of the bar elements in this type of modeling lead to another description of this structure namely micro-modeling strategy. In this strategy, units and mortars are modeled separately and all inelastic behavior of the masonry wall is supposed to happen in mortars. Hence, special attention is paid to development of a reliable description of material properties for these elements using an accurate constitutive law. Three dimensional representation of a masonry wall in this work enhances the capability of existing methods to predict the masonry behavior under both in-plane and out-of-plane loadings. Firstly, failure envelopes including tension cut-off and the Mohr-Coulomb yield surface are assigned to interface elements in GEFDyn finite element software. Then, the elstoplastic constitutive law is improved by adding a compression cap to the yield surfaces in order to include compressive failure of masonry in the interface element. In the new model, softening behavior for tensile and compressive strength as well as cohesion of mortar is considered. The ability of both models to reproduce the pre- and post-peak behavior of the masonry wall is verified by comparing the numerical results with experimental data. The importance of defining the compression failure of masonry by limiting the shear strength of the wall with its compressive strength is shown by comparing the obtained results with those of a real test. The results showed that the second model is capable to simulate the behavior of masonry wall with a good accuracy. Then, the effect of initial stresses and geometrical properties of the wall such as opening and aspect ratio and material properties of the mortar like its cohesion, tensile strength and compressive strength, on lateral strength and failure mechanism of the masonry walls are demonstrated. Moreover, in order to comprehend failure characteristics damage indexes based on the total length of cracks in different rows and columns of mortars are introduced and compared for different configurations. The lengths of sliding in horizontal mortars and opening in vertical ones are the most important parameters that control the behavior of the wall. Finally, the relation between different cracking profiles and contributing material properties are summarized into a table.

The development of lightweight concretes has made a contribution to advances in structural design. It would be useful to further improve the mechanical properties of lightweight concrete formulations whilst enhancing their resistance to fire degradation and reduced thermal conductivity. Improving the sustainability of any new proposed lightweight concrete formulation is desirable, for example by the inclusion of waste stream components into the formulation.This thesis describes an investigation of the mechanical, thermal and fire resistance properties of a new type of expanded clay lightweight concrete formulation in which varying quantities of sand are replaced by crushed glass aggregate, in conjunction with the addition of metakaolin (which may be available as a waste component from the manufacture of paper) as a partial replacement for the cement. The investigation involved short and long-term laboratory testing of a range of mechanical and thermal properties of individual concrete formulations and small scale structural elements consisting of masonry blocks made from these formulations (so called wallettes). An extensive programme of Finite Element Analysis using Abaqus was also performed.The results obtained show that it is possible to produce a structural expanded clay lightweight concrete that possesses good thermal properties by incorporating of ground glass and metakaolin. Compressive and splitting tensile strengths, as well as the modulus of elasticity, increased with an increase in the metakaolin content, while concrete density decreased. Reductions in thermal conductivity and improvements in fire resistance criteria were also observed in comparison with conventional lightweight concrete mixtures. For example, measured thermal conductivity values ranged from 0.092 W/m.K to 0.177 W/m.K, and the insulation criterion (an indicator of resistance to fire) reached up to 110 minutes for a concrete member with a thickness of 29 mm. The highest resistance to the effects of high temperatures was observed for concrete mixes containing either 15% or 30% recycled glass with 10% metakaolin.The maximum axial loads at failure were 474 kN and 558 kN for reference and modified wallettes respectively, implying corresponding bearing capacities of 7.1 MPa and 8.3 MPa. The critical path of the failure mode was similar for all of the wallettes tested and normally began underneath the load point, then passed through the concrete blocks and head joint to reach the toe of the wallette. The masonry wallettes formulated using reference lightweight concrete blocks exhibited failure due to explosive spalling at 400 oC with no applied mechanical load, whereas the second type of masonry wallettes (the modified wallettes) did not show such behaviour.The results of Finite Element Analysis showed that the coefficient of thermal convection had the most influence upon the insulation criterion. From a structural perspective, the key parameters were the value of penalty stiffness and imperfections in wallette construction. In general, a close agreement between the measured and simulated results was observed for both the thermal and structural finite element models at ambient and high temperatures.

Unreinforced masonry (URM) walls are often used as load-bearing or infill walls in buildings in many countries. Such walls are also commonly found in existing and heritage buildings in Canada. URM walls are strong structural elements when subjected to axial loading, but are very vulnerable under out-of-plane loads. This type of loading may come from different sources , including seismic or blast events. When subjected to blast, wall elements experience large pressures on one of their faces due to the high pressure produced in the air when an explosion takes place. This wave of compressed air travels in a very short time and hits the wall causing immense stresses, which result in large shear and bending demands that may lead to wall failure, and the projection of debris at high velocities that can injure building occupants. This failure process is highly brittle due to the very low out-of-plane strength that characterize such walls. In the past years, many investigations have been carried out to enhance the structural behaviour of unreinforced masonry walls under out-of-plane loading. Different strengthening methods have been studied, which include the use of polyurea coatings, the application of advanced fiber-reinforced polymer (FRP) composites or the use of concrete overlays in combination with high performance reinforcement. Fabric-reinforced cementitious matrix (FRCM) is a new composite material that overcomes some of the drawbacks of FRP. This composite material consists of applying coatings which consist of one or more layers of cement-based mortar reinforced with a corresponding open mesh of dry fibers (fabric). This material has been studied as a strengthening technique to improve in-plane and out-of-plane capacity of existing URM walls as well as other structural elements, mostly under seismic actions. This thesis presents an experimental and analytical study which investigates the effectiveness of using FRCM composites to improve the out-of-plane resistance of URM walls when subjected to blast loading. As part of the experimental program, three large-scale URM masonry walls were constructed and strengthened with 1,2 and 3 layers of FRCM using unidirectional carbon fabrics. In all cases the specimens were built as load-bearing concrete masonry (CMU) walls. To increase shear resistance, two of the walls were also grouted with a flowable self-compacting concrete (SCC) mortar. Blast tests were conducted using the University of Ottawa Shock Tube and the results are compared with control walls tested in previous research at the University of Ottawa. The experimental results show that the FRCM retrofit significantly improved the blast performance of the URM load-bearing walls, allowing for increased blast capacity and improved control of displacements. The performance of the retrofit was found to be dependent on the number of retrofit layers. As part of the analytical research, Single Degree of Freedom (SDOF) analysis was carried out to predict the blast behaviour of the strengthened walls. This was done by computing wall flexural strength using plane sectional analysis and developing idealized resistance curves for use in the SDOF analysis. In general, the analysis procedure is found to produce reasonably accurate results for both the resistance functions and wall mid-height displacements under blast loading.

Reinforced concrete block shear walls (RCBSWs) are used as seismic force resisting systems in low- and medium-rise buildings. However, attributed to their nonlinear behavior and composite material nature, accurate prediction of their seismic performance relying only on mechanics is challenging. This study introduces multi-gene genetic programming (MGGP)— a class of bio-inspired artificial intelligence, to uncover the complexity of RCBSW behaviors and develop simplified procedures for predicting the full backbone curve of flexure-dominated fully grouted RCBSWs under cyclic loading. A piecewise linear backbone curve was developed using five secant stiffness expressions associated with cracking, yielding, 80% ultimate, ultimate, and 20% strength degradation (i.e., post-peak stage) derived through controlled MGGP. Based on the experimental results of large-scale cyclically loaded RCBSWs, compiled from previously reported studies, a variable selection procedure was performed to identify the most influential variable subset governing wall behaviors. Utilizing individual wall results, the MGGP stiffness expressions were first trained and tested, and their accuracy was subsequently compared to that of existing models employing various statistical measures. In addition, the predictability of the developed backbone model was assessed at the system-level against experimental results of two two-story buildings available in the literature. The outcomes obtained from this study demonstrate the power of MGGP approach in addressing the complexity of the cyclic behavior of RCBSWs at both component- and system-level—offering an efficient prediction tool that can be adopted by relevant seismic design standards pertaining to RCBSW buildings. / Thesis / Master of Applied Science (MASc)

Steel flexural yielding arms can be an effective energy dissipation device for several seismic force resisting systems, including controlled rocking masonry walls. In controlled rocking masonry walls, uplift of the wall from the foundation is allowed in a way that can localize damage and minimize post-earthquake residual drifts. However, along with other modes of failure, sliding of the rocking walls can increase drifts and damage if not adequately addressed. Controlled rocking systems have different alternatives to prevent sliding, which include the use of additional mechanical components (e.g. metal stoppers) at the corners to resist lateral forces while allowing the wall rocking motion. However, these mechanical components hinder the constructability of the wall in some cases. The use of an energy dissipation device (i.e. steel flexural yielding arm) to also prevent the wall sliding mechanism has not been fully explored to date. The development of an easily replaceable energy dissipation device with the ability to simultaneously resist sliding demands is expected to maintain the overall performance of controlled rocking masonry walls, while also enhancing post-earthquake repairability. The objective of the current study is to experimentally investigate the effect of axial forces on the behaviour of steel flexural yielding arms under cyclic loading. In this respect, the study first presents a description of the experimental program, test setup, and instrumentation. Next, the experimental results of the tested specimens are discussed in terms of the effect of axial forces on the load, displacement, and energy dissipation capacities of the tested devices. Finally, new design equations that account for axial forces are proposed and verified against the experimental data along with a finite element model. Based on the results, recommendations are given for the further development of externally attached and replaceable flexural yielding arms for controlled rocking masonry walls. / Thesis / Master of Applied Science (MASc) / Controlled rocking masonry walls can be a cost-efficient alternative to traditional masonry shear walls because of their enhanced performance, specifically to reduce and localize structural damage induced by seismic loads. However, a controlled rocking wall requires additional energy dissipation devices or post-tensioning techniques to compliment the rocking wall to achieve the desired performance. This thesis explores and improves a type of energy dissipation device for controlled rocking masonry walls and aims to provide detailed design specifications for professional engineers. A design and considerations from previous studies are discussed, followed by the experimental validation, and finally new design equations are proposed for this type of reliable, flexural energy dissipation device.

In this research some kinds of masonry walls have been used as internal divisions in three Brazilian dwelling buildings to determine the airborne sound reduction, by experimental tests in field and computer simulations. The masonry walls studied are composed by massive bricks, bored ceramic blocks (6 and 4 holes) and structural (7 and 10 MPa), with mortar lining in both sides. The acoustic evaluations, in field, were accomplished according to the international rules ISO 140 part 4, ISO 717 part 1 and ISO 354. The determination of the airborne sound reduction among places it was accomplished from a direct and indirect sound transmission of constructive elements of the edifications, according to the EN 12354 rule part 1 and using a commercial computer program. The mainly results of this research showed the weighted values of the level standard difference (DnT,w) vary from 37 to 44 decibels to the evaluated walls. It was also observed the difference of 2 dB among the weighted values of the level standard difference (DnT,w) and the apparently sound reduction (R w). Almost all the masonry walls evaluated reached the minimum recommended values by the NBR 15575. In general, it happened a relation between the experimental results and the computer simulations, mainly with the weighted values relation and the isolation curves of the structural masonry walls. The computer simulation of the airborne sound transmission can be a good project tool, besides the initial datas don t represent properly the masonry material components evaluated, due to the national datas more complete and precise. / Neste trabalho são avaliadas alguns tipos de paredes de alvenaria utilizadas como divisórias internas em três edifícios habitacionais brasileiros para determinar a redução sonora aérea, através de ensaios experimentais em campo e de simulações computacionais. As paredes de alvenaria estudadas são compostas por tijolos maciços, blocos cerâmicos furados (6 e 4 furos) e estruturais (7 e 10 MPa), com revestimento de argamassa em ambos os lados. As avaliações acústicas, em campo, foram realizadas de acordo com as normas internacionais ISO 140 parte 4, ISO 717 parte 1 e ISO 354. A determinação da redução sonora aérea entre ambientes foi realizada a partir da transmissão sonora direta e indireta dos elementos construtivos das edificações, conforme a norma EN 12354 parte 1 e utilizando um programa computacional comercial. Os resultados principais desta pesquisa mostram que os valores ponderados da diferença padronizada de nível (DnT,w) variaram de 37 a 44 decibéis para as paredes avaliadas. Também, foi observada uma diferença de 2 dB entre os valores ponderados da diferença padronizada de nível (DnT,w) e do índice de redução sonora aparente (R w). Praticamente, todas as amostras de paredes de alvenaria avaliadas atingiram os valores mínimos de desempenho recomendados pela NBR 15575. Em geral, ocorreu uma boa correlação entre os resultados experimentais e as simulações computacionais, principalmente com relação aos valores ponderados e as curvas de isolamento das paredes de alvenaria estrutural. A simulação computacional da transmissão sonora aérea pode ser uma boa ferramenta de projeto, apesar dos dados de entrada não representarem fielmente as propriedades dos materiais componentes das alvenarias avaliadas, devido à carência de dados nacionais mais completos e precisos.