1,720,963 research outputs found
Reduced-order Models for Simulating Coupled Geometric Instabilities in Steel Beam-columns Under Inelastic Cyclic Straining
No full textNumerical models that can simulate coupled geometric instabilities in steel beam-columns are required for the seismic assessment of certain steel moment-resisting frames. Reliably simulating coupled instabilities requires that the steel material is precisely characterized under inelastic cyclic straining. Full continuum finite element (CFE) models can be used in this context, however, reduced order models are preferred for building-level simulations because of their lower computational cost. Concentrated plasticity models are a typical reduced order approach, although findings from recent full-scale experiments conducted on steel beam-columns have highlighted their limitations in simulating component behavior.
The aim of this thesis is to propose accurate reduced-order simulation models for steel beam-column components to simulate coupled buckling at a diminished computational expense compared to full CFE approaches. This goal is achieved by using component macro models that couple CFEs in critical regions with beam-column elements elsewhere. The specific objectives related to the aim of this thesis are to: (i) advance the state-of-the-art in constitutive modeling for structural steels subjected to earthquake-induced inelastic straining; (ii) develop an efficient method of coupling beam-column and CFE domains that incorporates torsion-warping; and (iii) develop general recommendations for modeling wide flange beam-column components subjected to inelastic cyclic straining using the macro model.
This thesis developed a constitutive model for mild structural steels to improve upon the initial yield behavior of a classic metal plasticity model by accounting for the discontinuous yielding phenomenon. Constitutive model calibration methodologies were developed using constrained optimization for the cases when the material's cyclic behavior is known and when it is unknown. Simulated geometric instabilities were shown to be sensitive to the constitutive model's input parameters in steel beam-columns of particular geometries subjected to multiaxis loading. Coupling methods that included torsion-warping were developed using multipoint constraint equations. Findings indicate that including torsion-warping in the coupling formulation is critical for steel beam-columns that are susceptible to coupled local and lateral-torsional instabilities. The proposed macro model is efficient for the investigated range of steel beam-columns: it reduces computational cost metrics in benchmark CFE analyses by around 50 %. It is also accurate, as the average error between benchmark CFE and macro model analyses is only 3 %.
The advances in material modeling made by this thesis can be used to reduce the uncertainty in steel component simulations. This enables analysts to better comprehend component behavior through simulations and improves simulation-assisted design. Component models that explicitly simulate geometric instabilities and material inelastic behavior at lower computational costs are important in probabilistic assessments and uncertainty quantification. They may be especially useful, for example, in benchmarking concentrated plasticity models and in the process of developing new structural systems.RESSLA
Experimental Behavior and Nonlinear Modeling of iron-based Shape Memory Alloys (SMAs) under Inelastic Cyclic Straining
No full textShape memory alloys (SMAs) have gained considerable attention in a broad range of engineering applications. In particular, iron-based SMAs (Fe-SMAs) have been recently developed and used as a cost-effective method for prestressed-strengthening of civil structures. Previous studies have shown that Fe-SMAs offer a strong shape memory effect (SME), however, a negligible superelastic behavior. The potential use of Fe-SMAs in seismic design and retrofit applications including supplemental damping is not yet clear and requires the further understanding of the material behavior under large amplitude cyclic inelastic straining. This thesis discusses key findings from a material-level experimental program that involved Fe-SMA round coupons subjected to a broad range of uniaxial cyclic strain histories representative of earthquake loading. Also, this work discusses the nonlinear modeling of Fe-SMAs under cyclic tension/compression straining.SGCRESSLA
Updates to the ASCE-41-13 Provisions for the Nonlinear Modeling of Steel Wide-Flange Columns for Performance-based Earthquake Engineering
Get PDFPerformance-based earthquake engineering requires numerical models that are able to reliably predict the expected component behavior of buildings under seismic excitations. The nonlinear modeling guidelines provided in ASCE-41-13 have historically been used in this context by practicing engineers. However, for steel wide-flange columns, the recommendations are primarily based on experimental data that was fairly limited until recently. This paper addresses many of the limitations present in ASCE-41-13 for the modeling of steel wide-flange columns. Recent experimental data from large- and full-scale tests on wide-flange steel columns, supplemented with detailed finite element studies, has been collected for a wide range of column cross-sections and applied compressive axial loads. Multiple regression analysis is utilized to develop multivariate predictive equations for the seismic response of steel wide-flange columns. It is found that the primary contributors that dominate the column response are the local web slenderness, member slenderness and the applied axial load ratio due to gravity loading. Guidelines for developing nonlinear component models for steel columns that can be directly used in both nonlinear static and dynamic analysis procedures are provided. The predicted responses are validated against test data that was not part of the original database. Furthermore, recommendations are proposed for modeling wide-flange columns subjected to varying axial loads as well as bidirectional loading; and a new limit for force-controlled elements is proposed for columns under high axial compressive loading and lateral drift demands.RESSLA
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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