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Shell modelling strategies for the assessment of punching shear resistance of continuous slabs
No full textPunching shear resistance formulation provided by Model Code 2010 is calibrated on the basis of experimental tests on isolated slabs supported on columns. According to Level of Approximation approach, several quantities are required for the design punching shear resistance assessment, like the resisting moment and the radius of the line of moment contraflexure. In this paper specific formulations are provided to adjust these quantities in order to take into account for moment redistribution and compressive membrane action effects. The punching shear resistance, mostly investigated for axisymmetric cases, in terms of loading and boundary conditions, will be analysed referring to actual rectangular RC continuous floors with orthogonal reinforcement layouts, largely adopted in practice. The results of nonlinear finite element analyses, carried out using PARC_CL crack model, are post-processed according to the Critical Shear Crack Theory to predict the punching shear strength of the continuous slab. The presented numerical procedure is validated comparing the obtained results with experimental measurements of a continuous slab tested by Ladner et al
Shear strength evaluation of RC bridge deck slabs according to CSCT with multi – layered shell elements and PARC_CL Crack Model
No full textThe shear resistance of RC slabs without shear reinforcement subjected to concentrated loads
near linear support is usually calibrated on the base of tests on one – way slabs with rectangular
cross section. However, the actual behavior of slabs subjected to concentrated loads is described
properly by a two-way slab response. The aim of this paper consists in the evaluation of the shear
resistance of bridge deck slabs using analytical formulations and Nonlinear Finite Element Analyses
(NLFEA). The obtained numerical results are consequently compared with experimental
observations from two test campaigns. The case studies were analysed by NLFE analyses carried
out using the constitutive Crack Model PARC_CL (Physical Approach for Reinforced Concrete under
Cycling Loading) implemented in the user subroutine UMAT.for in Abaqus Code. In order to predict
properly global and local failure modes through a NLFE model, a multi – layered shell modelling
has been used. As shell element modelling is not able to detect out – of – plane shear failures, the
ultimate shear resistance of these slabs is evaluated by means of a post – processing method
according to the Critical Shear Crack Theory (CSCT)
Interaction between Longitudinal Bending Moment and Transverse Shear Strength in RC Deck Slabs of Hollow Box Bridges
No full textDue to the introduction of novel code provisions, the safety verification of existing structures and infrastructures has become a great issue. Analytical formulations based on sectional analysis are sometimes too conservative to optimize a strategy for intervention on existing structures, therefore non-linear finite element analyses are used to exploit the maximum overall capacity of the members under investigation. For example, membrane actions developing in continuous slabs or bridge decks can be considered by using finite element analyses able to take into account for mechanical and geometrical nonlinearity. In particular, this work deals with the interaction between longitudinal bending moment and transverse shear strength of a reinforced concrete (RC) existing hollow-box bridge built in Switzerland. In the perspective of Level of Approximation Approach proposed by the Model Code 2010, the shear strengths of a bridge deck have been calculated by adopting Model Code 2010 formulations, Critical Shear Crack Theory (CSCT) and Non-Linear finite element analyses. NLFEA have been carried out with the "PARC CL2.0 crack model" implemented in the ABAQUS program at the University of Parma, using a multi-layered shell modeling in order to predict global and local failures. This numerical investigation highlights that, even for design purposes, the interaction between longitudinal hogging moment and transverse shear strength may be significant in the assessment of the shear resistance leading sometimes to non-conservative predictions
Modelling of Time-Dependent Effects of Reinforced Concrete Flat Slabs
No full textThis paper proposes a non-linear finite element model to compute the time-dependent behaviour of reinforced concrete
(RC) structures under service loads. The model, called PARC_CL 2.1, is based on a smeared and fixed crack approach in which the
effects of shrinkage and creep of concrete were implemented. The creep and shrinkage of the concrete are taken into account using
the Model Code 2010 formulations, opportunely modified with corrective coefficients. The proposed model is validated by studying
the nonlinear response of RC continuous flat slabs. From the analyses, it is observed that the computed development of deflections
and cracking with time are in good agreement with corresponding experimental result
Verification of deflections and cracking of RC flat slabs with numerical and analytical approaches
No full textThe Serviceability Limit States (SLS) of reinforced concrete structures, where cracking and deflection limits are verified in the design process, are directly related to time-dependent properties of concrete. In this study, the effects of creep and shrinkage of concrete, implemented in a Finite Element Model for Non-Linear Analysis, are in-deeply investigated for reinforced concrete flat slabs at SLS and used as basis for the development of an analytical framework. In particular, the paper focuses on: (i) the description of the FE model, (ii) the comparison between the numerical and experimental results of some reinforced concrete (RC) flat slab tests from literature characterized by different mechanical properties, span-to-depth ratios, boundary conditions and loading histories and (iii) the development of an analytical framework for the evaluation of long term-term deflections and crack openings in hogging regions of flat slabs near columns. Based on the findings, useful insights for the evaluation of the long term-term deflections and crack opening in the context of Serviceability Limit States are provided for practical purposes
Approaches for suitable modelling and strength prediction of reinforced concrete slabs.
No full textDespite the advances on the understanding and modelling of shear and punching shear failures, the application of actual design models to some situations remains still complex. This is for instance the case when significant redistributions in the shear field may happen as for concentrated loads applied near linear supports (typical situation of deck slabs of bridges) or for continuous flat slabs supported on columns. Accounting for the potential shear field redistributions implies performing nonlinear modeling of the structure, considering both the bending and shear loss of stiffness after cracking and/or reinforcement yielding. In addition, other significant phenomena such as compressive membrane action and moment redistribution may also develop influencing the shear/punching strength.
In this paper, a general methodology for analyzing the punching shear strength of continuos slabs is presented.. This is performed by using the -nonlinear finite element analysis (NLFEA) based on PARC_CL crack model. The NLFEA results - are then combined with the failure criterion of the Critical Shear Crack Theory to predict the punching shear strength of the member.
The results of this approach are compared against an actual flat slab supported on 16 columns tested in EMPA (1977), showing consistent agreement and explaining the observed behavior and load redistributions. Furthermore, the influence of moment redistribution and compressive membrane action will be analyzed and compared to current codes of practic
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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