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Dynamic response of structures with geometrically softening components including foundation interaction
No full textThe effects of material nonlinearity and geometric instabilities of a bracing system of a dynamically loaded steel frame, as well as nonlinear soil-structure interaction are studied in this thesis. To investigate the response of a frame subjected to severe dynamic loads, a model of the force-displacement relationship of the bracing system is developed to account for the inelastic, post-buckling behavior of a brace subjected to strong compressive loads. This thesis also develops a model of the force-deformation relationship of the foundation-soil interface, confining the study only to the slide mode of failure. From these models, a softening behavior for the bracing system and a hyperbolic load-deformation behavior of the interface are proposed. It is shown that the structural response of a frame is significantly affected when the analysis includes both the effects of softening of the bracing system and soil-structure interaction
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A Simplex-based search for critical non-circular slip surfaces
No full textSlope stability problems with non-circular slip surfaces have been characterized as a problem in optimization in which the safety factor expression is the function to be minimized. The Simplex Method of Nelder and Mead (1965), one of the most powerful direct search methods, has been implemented into program STABL5 (Carpenter et al, 1985) to examine the feasibility of using advanced optimization principles in conjunction with the relatively high problem dimension associated with non-circular slip surfaces. Parametric studies were performed on LSLIP1 in order to determine recommended values for the various input parameters. STABL5 and the revised code LSLIP1 were utilized to solve five slope problems representing a wide range of conditions. The revised code with its built-in Simplex search strategy proved to be more accurate, efficient and reliable than the original code with the random grid search
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Sand stabilization using waste plastics
No full textA study on the possible use of melted waste thermoplastics to stabilize soils, and produce plastic-soil structural composites is presented. Specifically, the effects of melted thermoplastics on the shear strength, and creep characteristics of sands are examined. An extensive experimental program was conducted to examine the strength and creep characteristics of different plastic-sand compositions. It was found that increasing plastic content in the sand results in stronger, and stiffer soils with negligible creep deformations for loads which are at least 50% of the strength of the composite. It is expected that injection of melted waste thermoplastics in sands can improve significantly the engineering characteristics of foundation, and slope stability of sands. Other potential applications include construction of structural elements, bricks, etc
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Constitutive modeling of dilatant soils with associative kinematic hardening plasticity
No full textIn this study, a set of rules is established, which when implemented in the modeling of dilatant soils, within the framework of associative plasticity, enables very successful shear and dilatancy predictions. The proposed approach is based on a number of principles, the most important of which are: (1) The plasticity model must have a loading surface that hardens kinematically, and a failure surface that is perfectly plastic. (2) Experimental evidence shows that uniformly deformed sand samples dilate with a constant rate when they reach their ultimate strength value, while critical state is only achieved at very large strains. There is a unique point A on the loading surface that corresponds to the experimentally observed dilatation rate. The hardening rule must, therefore, ensure that the stress point approaches A as it approaches the failure surface. These principles are implemented in a plasticity model and compared to numerous published monotonic and cyclic tests, with varied stress paths, performed on a true triaxial apparatus. The agreement between experimental data and theoretical predictions is excellent
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Consolidation of clays using the triaxial apparatus
No full textThe calculation of a consolidation settlement is an important problem encountered in the foundation of buildings. Due to need for simplicity engineers are mainly using the one dimensional theory of Terzaghi for calculations of consolidation settlements with time. Consolidation tests are still performed in most laboratories with the traditional oedometer cell. Although the results of the oedometer can provide relatively reliable results, they are not equally effective for the calculation of the rate of consolidation. This primarily because of the inability of the oedometer cell to obtain full saturation of the sample. To ensure full saturation, back pressure must be applied which is not possible for conventional oedometer cell. The alternative use of the triaxial cell to examine the consolidation behavior of soils is discussed here
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Dilatancy effects on the constitutive modeling of granular soils
No full textUnique features of behavior of granular materials make constitutive modeling of these materials a challenge that has not yet been answered completely. Because volume changes are so important for the type of behavior exhibited by frictional materials, it is important to correctly incorporate them in constitutive models, both in terms of their rate of development and their magnitude. In this study a number of consolidated drained triaxial tests are performed to find those features of sand behavior that can be considered "material parameters" and can be used for constitutive modeling of granular soils. Special attention is given to those features of material behavior that are related to dilatancy. A number of published experimental data are also analyzed and useful trends of soil behavior are found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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