Reinforced concrete deep beams are vital structural members serving as load transferring elements. The behavior of reinforced concrete deep beams is complex. Nonlinear distribution of strain and stress must be considered. Prior to 1999, ACI 318 Codes included an empirical design equation for reinforced concrete deep beams. Since 2002, the strut and tie model and nonlinear analysis have been required. However, both methods have disadvantages of complexity or lack of transparency. The objective of this study is to produce a simple, reliable design equation for reinforced concrete deep beams. A nonlinear finite element program, ATENA, was used for analyzing and predicting the behavior of concrete and reinforced concrete structures. First, applicability of ATENA was verified by developing the computer models of simply supported and two span continuous deep beams based on Birrcher’s tests of simply supported deep beams. Tests by Rogowsky and Macgregor and by Ashour are the basis for the models of continuous two span deep beams. Those tests were selected because the researchers reported adequate details of the experimental program and on specimen behavior. Then a series of simply supported and two span continuous deep beam models were developed based on the details and geometry of Birrcher's beams. The computer models were used to investigate the following parameters: the compressive strength of concrete, shear span to depth ratios, longitudinal reinforcement ratios, web reinforcement, effect of member depth, and loading conditions. Finally, a proposed design equation for shear strength of reinforced concrete deep beams was derived based on the observed the behavior of reinforced concrete deep beam tests, the results of the analytical study, and a plastic truss model. The proposed equations were in good agreement with test values and provide an alternate approach to current design procedures for deep beams. / text

Split Concrete Model (SCM) is a unified approach towards modeling shear behavior in concrete. SCM is essentially a rational model which is evaluated and modified using a large experimental database.The shear strength of the concrete beam is modeled as the sum of the contribution of concrete, transverse reinforcement, longitudinal reinforcement and bond between concrete and longitudinal reinforcement. Concrete does not contribute to the shear strength after the formation of the crack. In SCM, this is shown to be accurately modeled by only considering the second branch of the critical crack while computing the contribution of concrete towards shear strength of the beam. Formation of the second branch of the critical crack and immediate subsequent failure of the beam has been compared to the split-cylinder test, which forms the conceptual basis of SCM.SCM computes the concrete contribution using the split tensile strength and the area under compression of the concrete beam. For cases where a split-cylinder test is not performed, a mathematical model is proposed to compute the split tensile strength using the compressive strength of concrete available from experimental results. This model is proposed using advanced statistical methods, including weighted residuals and Box-Cox transformation and is validated using various statistical procedures. The transverse reinforcement contributes to the shear strength of the concrete beam only after the formation of the crack. In SCM, this is shown to be accurately modeled by only considering the first branch of the critical crack while computing the contribution of the transverse reinforcement towards shear strength of the beam, instead of the conventional approach of considering the entire length of the crack. The contribution of the longitudinal steel and bond between concrete and longitudinal steel and concrete is accurately modeled unlike the conventional approaches which do not consider this contribution.Evaluation using the database shows that SCM can predict accurate results for all ranges of strength, depth, reinforcement ratio, and shear span to depth ratio of the beam. This shows that all the influencing parameters for concrete shear strength have been correctly modeled in SCM. SCM gives more accurate results as compared to current codified approaches as verified with design examples. Finally, specific recommendations have been made indicating how the shear design requirements in the current ACI code can be modified.

Composite liners are used in landfills to isolate solid waste from the local environment. The combination of a high-density polyethylene (HDPE) geomembrane and compacted clay liner (CCL) is commonly used worldwide. In the Ontario region, bentonite sand mixtures (BSMs) and the local clay i.e. Leda clay, can be considered as appropriate CCL materials. However, the interface failure between smooth HDPE and CCL is a critical issue for landfill safety. The shear stress behavior and strength parameters at the interface between the HDPE and CCL can be affected by many factors, such as temperature and chemicals. The temperature difference between winter and summer in the Ontario region is approximately 50°C, which causes a freeze-thaw (F-T) phenomenon in local landfills. Leachate and heat are generated during the solid waste stabilization process. Landfill leachate usually contains a high concentration of cations, which can carry heat, thus affecting the landfill liner properties. As a result, the interface shear stress behavior and strength parameters are affected by the aforementioned conditions. In this thesis, a series of experiments were conducted on the shear stress behavior at the interface of Leda clay / HDPE and bentonite sand mixture (BSM) / HDPE. In order to understand the influence of the F-T phenomenon, the samples were tested by varying the number of F-T cycles. Meanwhile, in order to understand the combined influence of cations and heat, the samples were saturated with different solutions, i.e. distilled water, potassium chloride and calcium chloride solutions. Then they were cured in an oven with different temperatures and room temperature, respectively. All of the laboratorial shear tests have been performed by using a direct shear machine. Results show that the BSM /HDPE and Leda clay/ HDPE interfaces are both influenced by the F-T cycles. The BSM/HDPE interface shear of the samples between 0 and 5 F-T cycles has more obvious differences, while the friction angle of compacted Leda clay/HDPE exhibits distinct reduction in the first 3 cycles, after which, the difference becomes hard to differentiate. The results also indicate that both high temperature and high concentration of cations from leachate can slight reduce the interface shear stress of BSM/HDPE. However, the combined influence of thermal-chemical conditions is not much more obvious compared to the effects of a single thermal or chemical condition. The BSM materials, which were saturated with different solutions, are also tested by using X-ray diffraction to examine the mineral changes in the BSM. The calcium and potassium cations convert sodium-bentonite into calcium-rich bentonite and illite/semectie mixtures, respectively. Nevertheless, the changess of clay part caused by the combined effect of heat and leachate have limited influence on the BSM/HDPE interface shear behavior.

京都大学 / 0048 / 新制・課程博士 / 博士(地球環境学) / 甲第17802号 / 地環博第109号 / 新制||地環||22(附属図書館) / 30609 / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 勝見 武, 教授 三村 衛, 准教授 乾 徹 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DFAM

Advances in structural systems that resist extreme loading such as earthquake forces are important in their ability to reduce damages, improve performance, increase resilience, and improve the reliability of structures. Buckling resistant shear panels can be used to form new structural systems, which have been shown in preliminary analysis to have improved hysteretic behavior including increased stiffness and energy dissipating ability. Both of these characteristics lead to reduced drifts during earthquakes, which in turn leads to a reduction of drift related structural and nonstructural damage. Shear links are being used for seismic energy dissipation in some structures. A promising type of fuse implemented in structures for seismic energy dissipation, and seismic load resistance consists of a steel plate with cutouts leaving various shaped shear links. During a severe earthquake, inelastic deformation and damage would be concentrated in the shear links that are part of replaceable structural fuses, while the other elements of the building remain in the elastic state. In this study, by identifying the issues associated with general fuses previously used in structures, the behavior of the links is investigated and procedures to improve the behavior of the links are explained. In this study, a promising type of hysteretic damper used for seismic energy dissipation of a steel plate with cutouts leaving butterfly-shaped links subjected to shear deformations. These links have been proposed more recently to better align bending capacity with the shape of the moment diagram by using a linearly varying width between larger ends and a smaller middle section. Butterfly-shaped links have been shown in previous tests to be capable of substantial ductility and energy dissipation, but can also be prone to lateral torsional buckling. The mathematical investigations are conducted to predict, explain and analyze the butterfly-shaped shear links behavior for use in seismic structural fuses. The ductile and brittle limit states identified based on the previous studies, are mathematically explained and prediction equations are proposed accordingly. Design methodologies are subsequently conceptualized for structural shear links to address shear yielding, flexural yielding and buckling limit states for a typical link subjected to shear loading to promote ductile deformation modes. The buckling resistant design of the links is described with the aid of differential equations governing the links' buckling behavior. The differential equations solution procedures are developed for a useful range of link geometries and the statistical analysis is conducted to propose an equation for critical buckling moment. Computational studies on the fuses are conducted with finite element analysis software. The computational modeling methodology is initially verified with laboratory tests. Two parametric computational studies were completed on butterfly-shaped links to study the effect of varying geometries on the shear yielding and flexural yielding limit states as well as the buckling behavior of the different butterfly-shaped link geometries. It is shown that the proposed critical moment for brittle limit state has 98% accuracy, while the prediction equations for ductile limit states have more than 97% accuracy as well. Strategies for controlling lateral torsional buckling in butterfly links are recommended and are validated through comparison with finite element models. The backbone behavior of the seismic butterfly-shaped link is formulized and compared with computational models. In the second parametric study, the geometrical properties effects on a set of output parameters are investigated for a 112 computational models considering initial imperfection, and it is indicated that the narrower mid-width would reach to their limit states in lower displacement as compared to wider mid-width ones. The work culminates in a system-level validation of the proposed structural fuses with the design and analysis of shear link structural fuses for application in three buildings with different seismic force resisting systems. Six options for shear link geometry are designed for each building application using the design methodologies and predictive equations developed in this work and as guided by the results of the parametric studies. Subsequently, the results obtained for each group is compared to the conventional systems. The effect of implementation of the seismic links in multi-story structures is investigated by analyzing two prototype structures, with butterfly-shaped links and simple conventional beam. The results of the nonlinear response history analysis are summarized for 44 ground motions under Maximum Considered Event (MCE) and Design Basic Earthquake (DBE) ground motion hazard levels. It is shown that implementation of the butterfly-shaped links will lead to higher dissipated energy compared to conventional Eccentrically Braced Frame (EBF) systems. It is concluded that implementation of the seismic shear links significantly improves the energy dissipation capability of the systems compared to conventional systems, while the stiffness and strength are close in these two systems. / Ph. D. / Structural fuses are replaceable elements of a structure that are designed to yield and protect the surrounding members from damages, and then be accessible and replaceable after a major event. Several studies have indicated that steel plates with cutouts would have advantages for use in structural fuses. Having cutouts in a steel plate would make different shapes inside of the plate, which are called structural links. To have the same yielding condition all over the links, it is tried to better align the capacity of the links with the shape of the demand diagram caused by loading, which would be leading to the efficient implementation of the steel. In general, links are implemented to substantially increase the energy dissipation capacity of a structure and significantly reduce the energy dissipation demand on the framing members of a structure. For these purposes, various shapes have been proposed in this research study. The main feature of a replaceable link system is that the inelasticity is concentrated at the steel link while the beams and columns remain almost elastic. This study investigated the general behavior of the fuses, the applicability of them for space-constrained applications, the flexure, shear and buckling limit states affecting the behavior of the links. The computational analysis methodologies to model the links are explained and confirmed with the behavior of the different experiment tests as well as the proposed brittle limit state prediction equations. Subsequently, the two parametric studies are done to investigate the effect of geometrical properties on the links output results and establish prediction equations. The results from the analytical and computational studies for the seismic links are incorporated for seismic investigation of multi-story buildings. The results of seismic analysis of the two buildings are summarized for 44 ground motions.

Environmental conditions such as temperature inevitably impact the long term performance, strength and deformation characteristics of most materials in infrastructure applications. The mechanical and durability properties of geosynthetic materials are strongly temperature dependent. The interfaces between geotextiles and geomembranes as well as between granular materials such as sands and geomembranes in landfill applications are subject to temperature changes due to seasonal temperature variations as well as exothermic reactions occurring in the waste body. This can be a critical factor governing the stability of modern waste containment lining systems. Historically, most laboratory geosynthetic interface testing has been performed at room temperature. Information today is emerging that shows how temperatures in the liner systems of landfills can be much higher. An extensive research study was undertaken in an effort to investigate temperature effects on interface shear behavior between (a) NPNW polypropylene geotextiles and both smooth PVC as well as smooth and textured HDPE geomembranes and (b) sands of different angularity and smooth PVC and HDPE geomembranes. A temperature controlled chamber was designed and developed to simulate elevated temperature field conditions and shear displacement-failure mechanisms at these higher temperatures. The physical laboratory testing program consisted of multiple series of interface shear tests between material combinations found in landfill applications under a range of normal stress levels from 10 to 400 kPa and at a range of test temperatures from 20 to 50 °C. Complementary geotextile single filament tensile tests were performed at different temperatures using a dynamic thermo-mechanical analyzer (DMA) to evaluate tensile strength properties of geotextile single filaments at elevated temperatures. The single filament studies are important since the interface strength between geotextiles and geomembranes is controlled by the fabric global matrix properties as well as the micro-scale characteristics of the geotextile and how it interacts with the geomembrane macro-topography. The peak interface strength for sand-geomembrane as well as geotextile-geomembrane interfaces depends on the geomembrane properties such as hardness and micro texture. To this end, the surface hardness of smooth HDPE and PVC geomembrane samples was measured at different temperatures in the temperature controlled chamber to evaluate how temperature changes affect the interface shear behavior and strength of geomembranes in combination with granular materials and/or geotextiles. The focus of this portion of the experimental work was to examine: i) the change in geomembrane hardness with temperature; ii) develop empirical relationships to predict shear strength properties of sand - geomembrane interfaces as a function of temperature; and iii) compare the results of empirically predicted frictional shear strength properties with the results of direct measurements from the interface shear tests performed at different elevated temperatures.

[pt] O comportamento de vigas de concreto armado com barras de polímero reforçado com fibras de vidro (PRFV) submetidas ao esforço cortante tem diferenças quando comparada ao tradicional uso de armaduras de aço. O relativo baixo módulo de elasticidade e menor resistência ao carregamento transversal de barras de PRFV alteram a ação dos mecanismos de resistência e cinemática da fissura crítica ao cortante. Nesse contexto, a aplicação de fibras dispersas na matriz de concreto se coloca como uma possibilidade para buscar a redução da flexibilidade desse tipo de elemento. Sendo assim, este trabalho investiga o comportamento experimental de quatro vigas de concreto armado com barras de PRFV sem e com estribos e fibras de basalto. Utilizando-se da técnica de Correlação de Imagem Digital (CID), os campos de deslocamentos do vão de ruptura foram mapeados e, por meio de modelos constitutivos dos mecanismos resistentes à força cortante disponíveis na literatura, analisou-se o comportamento resistente das vigas. A quantificação de resistência através dos modelos constitutivos apresentou uma satisfatória correlação com os resultados experimentais. Além disso, a análise possibilitou uma melhor compreensão da contribuição dos mecanismos resistentes em diferentes estágios de carregamento. / [en] The shear behavior of reinforced concrete beams with Glass Fiber Reinforced Polymer Bars (GFRP) has differences when compared to traditional steel reinforcement. The relative low modulus of elasticity and the lower resistance to transverse loading of GFRP bars change the resistance mechanisms and kinematics of the critical shear crack. In this context, the application of dispersed fibers in the concrete matrix may be used to try to reduce the flexibility of this type of element. Therefore, this work investigates the experimental behavior of four reinforced concrete beams with GFRP bars with and without stirrups and basalt fibers. By using Digital Image Correlation (DIC) technique, the displacement fields of the failure span were mapped and, by means of constitutive models of the shear resistant mechanisms available in the literature, the resistant behavior of the beams was analyzed. The evaluation of resistance mechanisms through the constitutive models showed a satisfactory correlation with the experimental results. In addition, the analysis provided a better understanding of the contribution of each resistant mechanisms at different stages of loading.

La résistance au cisaillement des éléments en béton armé reste un sujet d'un grand intérêt pour l'ingénierie des structures civiles. En service, la plupart des éléments structuraux sont soumis à des sollicitations de cisaillement et/ou de poinçonnement avec un risque accru de rupture fragile. Différentes méthodes de calcul des résistances à l’effort tranchant existent, mais présentent des dispersions considérables notamment pour les éléments structuraux non armés transversalement. Ceci est dû principalement à la non-prise en compte de l’ensemble des mécanismes entrant dans le phénomène de cisaillement. L’objectif du présent travail de thèse est de contribuer à la compréhension des mécanismes de transfert de l’effort tranchant dans les poutres en béton armé. Pour cela, une campagne expérimentale est réalisée sur des poutres en béton armé sans armatures transversales et de différentes tailles afin d’étudier l’effet d’échelle sur l’effort tranchant. Le processus de fissuration marqué par la présence d’une fissure diagonale est analysé par deux techniques expérimentales : Corrélation d’images numériques et l’émission acoustique. Par la combinaison des résultats de la corrélation d'images et les jauges de déformations collées sur les armatures longitudinales, il est possible de distinguer la contribution du mécanisme d’engrènement des granulats et de l'action d’effet de goujon. L’influence de l’effet d’échelle sur chaque mécanisme de transfert est analysée par des modèles numériques et empiriques simplifiés en se basant sur les résultats expérimentaux à l’échelle locale. Les résultats confirment que l’engrènement des granulats joue un rôle décisif dans la contribution à la résistance de cisaillement pour les éléments en béton armé sans armatures transversales. Cette contribution dépend essentiellement des variables cinématiques(ouverture de fissure et glissement) et l’angle d’inclinaison de la fissure diagonale. Ce mécanisme est très dépendant de la taille de l’élément et de la forme de la fissure. / The shear strength of reinforced concrete elements remains a subject of great interest for the civil engineering structures. During service,most structural elements are subjected to shear and /or punching stresses with an increased risk of brittle failure. Different methods of calculation of shear strengths exist but have considerable discrepancy especially for the structural elements without transverse reinforcement. It is mainly by not taking into consideration all the mechanisms which are involved in the shear behavior. The objective of thisdoctoral thesis is to contribute towards the understanding of the shear force transfer mechanisms in reinforced concrete beams. For this,an experimental campaign is carried out on reinforced concrete beams without transverse reinforcement and of different geometrically similar sizes in order to investigate the size effect on the shear force. The cracking process manifested by thepresence of a diagonal crack is analyzed by two experimental techniques: Digital Image Correlation and Acoustic Emission. By combining the results of the digital image correlation and the strain gauges glued on the longitudinal reinforcement, it is possible to distinguish the contribution of the aggregate interlocking mechanism and the dowel action on the transfer of shear forces. The influence of size effect on each transfer mechanism is analysed by simplified numerical and empirical models based on experimental results at the local scale. The results confirm that the aggregate interlocking mechanism plays a critical role in the contribution to shear strength for reinforced concrete elements without transverse reinforcement. This contribution depends essentially on the kinematic variables (crack opening and sliding) and the angle of inclination of the diagonal crack. This mechanism is strongly dependent on the size of the element and the shape of the crack.

During the last four decades, fiber reinforced concrete has been increasingly used in structural applications. It is generally accepted that addition of steel fibers significantly increases tensile toughness and ductility, also slightly enhances the compressive strength. Although several studies have reported previously the favorable attributes of steel fiber reinforced concrete (SFRC), little general data is related to performance modeling. There are studies on the effect of fibers on compression, tension and shear behavior of concrete. As models proposed so far can, at best, describe only a few aspect of SFRC with a given type and amount of fibers, establishing simple and accurate generalized equations to describe the behavior of SFRC in tension, compression and shear that take into account the fiber type and content is essential. Therefore, a comprehensive experimental research on SFRC is conducted in University of Canterbury to develop generalized equations to represent the characteristics of SFRC. In this research, standard material tests of SFRC are carried out in tension, compression and shear to enable the parametric characterization and modeling of SFRC to be conducted. The tests are conducted using two different propriety fiber types (NovotexTM and DramixTM) with volumetric ratios ranging from 0 to 2 percent of the Novotex fibers and with 1 percent Dramix fibers. Compression tests are conducted on small and large cylinders. For characterization of tensile behavior, several different test methods are used including: direct tension of SFRC alone; SFRC with tension applied to an embedded longitudinal rebar; and flexural bending test. Similarly direct shear tests are conducted to investigate the additional shear resistance contributed by steel fibers. Variations in the results of different specimens are reconciled through normalization of stress and strain parameters. Based on the experimental results, empirical relations are derived for modeling and analysis of SFRC.

Geosynthetics are used in conjunction with soil/particulate materials to serve various functions like reinforcement, drainage, filtration and containment. The shear behavior of soil-geosynthetic interfaces hugely depends upon on the morphological properties of particulate materials and surface characteristics of geosynthetics. However, many researchers have ignored the effects of morphology, owing to the difficulty in finding the morphological characteristics of sand particles. Few of them used visual, manual and imaged based quantifications, which are not very effective. Also, the effects of particle size and morphology are often combined and the individual effect of these parameters cannot be easily separated. In addition to this, there are very few studies which have given importance to quantitative understanding of surface features/roughness of geosynthetics and almost all of them are limited to 2D surface measurements. The objective of this thesis is to understand the interface shear mechanisms of sand-geosynthetic systems through modified large interface direct shear tests coupled with morphological characterization of sands using advanced image based and optical techniques and surface topographical analysis of geosynthetics using 3D interferometry. The individual effects of particle size and morphology on interface shear mechanism are investigated by carefully selecting the sands having specific size fractions and different morphological characteristics. A new computational method based on image analysis is proposed in this study to quantify the morphology of sands (roundness, sphericity and roughness) more accurately by writing several algorithms and implementing them in MATLAB. The roundness and sphericity of sand particles in this method are quantified as per Wadell (1932) and Krumbein and Sloss (1963) respectively and the root mean square roughness is used as a measure of surface roughness. Out of total four sands, namely coarse sand (CS), medium sand (MS), fine sand (FS) and angular coarse sand (ACS) used in this study, CS, MS and FS have similar morphology and different particle sizes, whereas CS and ACS have same size and dissimilar morphology. The effects of size and morphology of sand particles on the interface shear behavior are examined through direct shear tests on dilative and non-dilative interfaces. After examining the boundary effects on deformation patterns analyzed using shear bands in conventional, fixed box and symmetric interface direct shear tests, symmetric interface direct shear test is observed to show uniformity in stresses and deformations across the shear box and hence the same is adopted in this thesis. Test results revealed that the peak interface friction and dilation angles in case of dilative interfaces are hugely dependent upon the interlocking between the sand particles and the asperities of geosynthetic material, which in turn depend on the relative size of sand particles and asperities. Highest interface shear strength is observed when the asperity size of the geosynthetic material matches with the mean particle size of sand, which is also manifested in terms of highest shear band thickness. Direct shear tests on non-dilative interfaces (sand-smooth geomembrane) revealed that interface friction angle depends on the number of effective contacts rather than the particle size. Morphology of sands is found to have major influence on the interface shear strength among all the parameters investigated. Results from interface shear tests are examined in the light of topographical analysis of sand particles and shear induced surface changes in geomembrane. Possible shearing mechanisms at the interface and the influence of particle size, morphology and normal stress on sliding or plowing are brought out from 3D surface roughness measurements using 3D optical profilometer. The stress-shear displacement response of sand-geomembrane interfaces are correlated to the surface changes on sheared geomembranes through visual observations and roughness quantifications. Medium sand used in this study could make more number of effective contacts with deeper grooves, resulting in highest interface friction. The number of grooves are less in case of coarse sand and the depth of grooves is less in case of fine sand, resulting in lesser interface friction for these two sands compared to medium sand, supporting the results of interface shear tests.