1,720,961 research outputs found
Finite element response sensitivity analysis using three-field mixed formulation: general theory and application to frame structures
No full textThis paper presents a method to compute response sensitivities of finite element models of structures based on a three-field mixed formulation. The methodology is based on the direct differentiation method (DDM), and produces the response sensitivities consistent with the numerical finite element response. The general formulation is specialized to frame finite elements and details related to a newly developed steel–concrete composite frame element are provided. DDM sensitivity results are validated through the forward finite difference method (FDM) using a finite element model of a realistic steel–concrete composite frame subjected to quasi-static and dynamic loading. The finite element model of the structure considered is constructed using both monolithic frame elements and composite frame elements with deformable shear connection based on the three-field mixed formulation. The addition of the analytical sensitivity computation algorithm presented in this paper extends the use of finite elements based on a three-field mixed formulation to applications that require finite element response sensitivities. Such applications include structural reliability analysis, structural optimization, structural identification, and finite element model updating
Finite element response sensitivity analysis of continuous steel-concrete composite girders
No full textFinite element response sensitivity analysis of steel-concrete composite beams with deformable shear connection.
No full textThe behavior of steel-concrete composite beams is strongly influenced by the type of shear connection between the steel beam and the concrete slab. For accurate analytical predictions, the structural model must account for the interlayer slip between these two components. In numerous engineering applications e.g., in the fields of structural optimization, structural reliability analysis, and finite element model updating, accurate response sensitivity calculations are needed as much as the corresponding response simulation results. This paper focuses on a procedure for response sensitivity analysis of steel-concrete composite structures using displacement- based locking-free frame elements including deformable shear connection with fiber discretization of the cross section. Realistic cyclic uniaxial constitutive laws are adopted for the steel and concrete materials as well as for the shear connection. The finite element response sensitivity analysis is performed according to the direct differentiation method. The concrete and shear connection material models as well as the static condensation procedure at the element level are extended for response sensitivity computations. Two steel-concrete composite structures for which experimental test results are available in the literature are used as realistic testbeds for response and response sensitivity analysis. These benchmark structures consist of a nonsymmetric, two-span continuous beam subjected to monotonic loading and a frame subassemblage under cyclic loading. The new analytical derivations for response sensitivity calculations and their computer implementation are validated through forward finite difference analysis based on the two benchmark examples considered. Selected sensitivity analysis results are shown for validation purposes and for quantifying the effect and relative importance of the various material parameters in regards to the nonlinear monotonic and cyclic response of the testbed structures
Nonlinear seismic response analysis of steel-concrete composite frames
No full textFrame finite-element models permit obtaining, at moderate computational cost, significant information on the dynamic response behavior of steel–concrete composite SCC frame structures. As an extension of conventional monolithic beam models, composite beams with deformable shear connection were specifically introduced and adopted for the analysis of SCC beams, in which the flexible shear connection allows development of partial composite action influencing structural deformation and distribution of stresses. The use of beams with deformable shear connection in the analysis of frame structures raises very specific modeling issues, such as the characterization of the cyclic behavior of the deformable shear connection and the assembly of composite beam elements with conventional beam–column elements. In addition, the effects on the dynamic response of SCC frame structures of various factors, such as the shear connection boundary conditions and the mass distribution between the two components of the composite beam, are still not clear and deserve more investigation. The object of this paper is to provide deeper insight into the natural vibration properties and nonlinear seismic response behavior of SCC frame structures and how they are influenced by various modeling assumptions. For this purpose, a materially nonlinear-only finite-element formulation is used for static and dynamic response analyses of steel–concrete frame structures using composite beam elements with deformable shear connection. Realistic uniaxial cyclic constitutive laws are adopted for the steel and concrete materials of the beams and columns and for the shear connection. The resulting finite-element model for a benchmark problem is validated using experimental test results from the literature for quasi-static cyclic tests. The paper then focuses on the numerical simulation, based on various modeling assumptions, of the eigenproperties and seismic response of a realistic two-dimensional five-story two-bay moment resisting frame made of steel columns and SCC beams and designed according to the Eurocode. It is found that the inclusion of the deformability of the shear connection in the finite-element model has a significant effect on the global dynamic response of SCC frame structures. In modeling this type of structures by using frame elements with deformable shear connection, a proper representation of the shear connection boundary conditions for all composite beams is crucial for accurate response simulation
Continuum soil-structure-interaction model of the LHPOST6 shaking table reaction mass at UC San Diego
No full textThe recently upgraded six Degree-of-Freedom Shaking Table, LHPOST6, at UC San Diego, underwent a series of forced vibration tests to evaluate the postupgrade dynamic response of the foundation-soil system. The resulting data were instrumental in obtaining frequency response curves of the system, which were used to determine its low-strain natural frequencies, effective viscous damping ratios, and reaction mass displacements. The extensive experimental data motivated the creation of a detailed Soil-Structure-Interaction model of the reaction mass-soil system. The structure and soil were modeled using 3D Finite Elements in STKO-OpenSees and calibrated with the acquired data via a parametric study. The 3D continuum FE
model and the calibration procedure based on a single soil parameter (shear wave velocity profile) proved to be an effective tool to reproduce the experimental results accurately. This paper describes the Finite Element model, its calibration, and validation. In addition, the paper provides suggestions to simplify continuum models and promote their use in professional practice. The objectives of this campaign, alongside the growing accessibility of high-performance computing, may serve as a step toward using SSI continuum models in the industry
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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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