1,720,968 research outputs found
Response sensitivity analysis of frame structures using finite elements based on three-field mixed formulation
No full textFinite element response sensitivities represent an essential ingredient for gradient-based optimization methods used to solve problems in structural optimization, structural reliability analysis, structural identification and finite element model updating [1]. Finite element response sensitivities are also invaluable for gaining deeper insight into the effects and relative importance of the various geometric, material, and loading parameters defining the structure and its loading
environment. Sensitivity analysis formulations have been developed for displacement-based finite element models [2] and, recently, for force-based frame elements [3]. The advantages gained in response
analysis by using finite element formulations more advanced than the classical displacementbased formulation can be further extended to the realm of response sensitivity analysis. A large body of research has been devoted to mixed finite element formulations since they were
first introduced in the pioneering work of Pian [4]. Several finite elements based on different variational principles have been developed and their accuracy and performance have been
thoroughly analyzed and improved. Nowadays, mixed finite elements are well established and largely adopted tools in a wide range of structural mechanics applications. Multi-field mixed finite element formulations were proposed, among others, for finite elements
widely used in the structural engineering community such as frame elements. Mixed frame elements are more accurate in nonlinear analysis than displacement-based elements and are a possible alternative to the recently established force-based elements.
This paper focuses on the formulation of finite element response sensitivity analysis, using the Direct Differentiation Method (DDM) [2, 3], in the case of a nonlinear three-field mixed approach derived from the Hu-Washizu variational principle [5], considering both quasi-static
and dynamic loadings. The general formulation for finite element response sensitivity analysis using the three-field mixed formulation is specialized and applied to frame finite element models. The results of the DDM are validated through the forward Finite Difference Method (FDM) using as application example a realistic steel-concrete composite frame structure subjected to quasistatic and dynamic loading, respectively. Both monolithic frame elements and composite frame elements with deformable shear connection [6] based on the three-field mixed formulation are included in this application example
Nonlinear finite element response sensitivity analysis of steel-concrete composite beams
No full textThe behavior of steel-concrete composite beams is strongly influenced by the type of connection between the steel beam and the concrete slab. For accurate analysis, the structural model must account properly for the interlayer slip between the components. This paper focuses on nonlinear finite element response sensitivity analysis using a displacement-based formulation for composite beams with deformable shear connection. Realistic uniaxial constitutive laws are adopted for the concrete and steel materials as well as for the
shear connectors. A non-symmetrical two-span composite beam structure for which experimental results are available is used as application example. The finite element response is validated through the experimental results available for monotonic loading condition. Then, the finite element response sensitivity analysis is
performed according to the Direct Differentiation Method (DDM) and validated through Forward Finite Difference (FFD) analysis. Selected results of the sensitivity analysis are presented in order to show the relative importance of concrete, steel, and shear connection material parameters
Nonlinear dynamic analysis of steel-concrete composite frame structures with full and partial shear connection under earthquake excitation
No full textVarious finite element (FE) models can be used for the analysis of steel-concrete composite (SCC) structures. Among available FE models, frame elements permit obtaining significant information at reasonable computational cost compared to more sophisticated two-dimensional (plate/shell) and three-dimensional (solid) elements. As an extension of conventional monolithic beam models, beams with deformable shear connection were specifically introduced and adopted for the analysis of SCC beams. Flexible shear connectors allow development of partial composite action, influencing structural deformation and distribution of stresses under service and ultimate load conditions. Furthermore, the shear connection can be responsible for collapse, e.g., when partial shear connection design is adopted, connectors fail due to limited ductility. Thus, a composite beam model with deformable shear connection has some important advantages over the common monolithic beam model, i.e., it allows a more accurate modelling of the structural behaviour, provides information on the slab-beam interface slip and shear force behaviour, permits to evaluate the effects of the interface slip on stress distribution, and enables to model damage and failure of the connectors. Applications of beam elements with deformable shear connection to the analysis of SCC frames have mainly concerned quasi-static behaviour, and there is limited experience on nonlinear dynamic analysis [1]. More attention is required by very specific modelling issues, such as the characterization of the cyclic behaviour of the deformable shear connection and the assembly of SCC beam elements with conventional beam-column elements. In addition, the influence of various factors (e.g., shear connection boundary conditions, mass distribution between the two components of the composite beam) on the dynamic response of SCC frame structures needs to be better understood through a systematic parametric study.
The objective of this work is to provide deeper insight into nonlinear dynamic analysis results of SCC structures and how different modelling assumptions affect these results. For this purpose, a materially-nonlinear-only FE formulation for static and dynamic analysis of SCC structures using displacement-based locking-free elements with deformable shear connection [2] is employed. Realistic uniaxial cyclic constitutive laws are adopted for the steel and concrete materials of the beams and columns and for the shear connection. Nonlinear dynamic seismic analysis results of two-dimensional moment resisting frames made of steel columns and composite beams are provided. These results and their discussion focus on: (i) the influence of partial composite action on the dynamic nonlinear analysis of SCC frames; (ii) the effects of different shear connection boundary conditions
Nonlinear dynamic analysis of steel-concrete composite frame structures under earthquake excitation
No full textComposite beams with deformable shear connection were specifically introduced as an extension of conventional monolithic beam models for the analysis of steel-concrete composite (SCC) structures in which the flexible shear connection allows development of partial composite action influencing structural de-formation 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 are still not clear and deserve more investigation. The object of this work is to provide deeper insight into the nonlinear seismic response behavior of SCC frame structures and how it is influenced by various modeling assumptions
Modeling issues in nonlinear dynamic finite element analysis of steel-concrete composite frame structures subjected to seismic excitation
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
Discours que le citoyen J. P. Conte a commencé de lire aux magistrats composant la Petite Cour criminelle
No full textAnalyse de Rivoire: Ce discours ayant été lu le 2 mai à la Société des Montagnards, sentinelles de la liberté, par le citoyen J. P. Conte, l'assemblée en demanda et en arrêta l'impression. Conte raconte la dispute suivie de coups qu'il eut avec Neff et adresse divers reproches à ce dernier sur sa conduite
Finite element response sensitivity analysis of continuous steel-concrete composite beams
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. This paper focuses on a procedure for response sensitivity analysis using state-of-the-art finite elements for composite beams with deformable shear connection. Monotonic and cyclic loading cases are considered. 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 (DDM); its analytical derivation and computer implementation are validated through Forward Finite Difference (FFD) analysis. Sensitivity analysis results are used to gain insight into the effect and relative importance of the various material parameters in regards to the nonlinear monotonic and cyclic response of continuous composite beams, which are commonly used in bridge construction
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
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