1,721,122 research outputs found
Implementation of Steel Constitutive Model Including Buckling in Parc_CL 2.1 Crack Model
Full text linkLacking of details in existing structures, like high value of stirrups spacing, causes a bad confinement of concrete and consequently high lateral deformations of longitudinal bars after the spalling of the concrete in case of cyclic loading induced by seismic actions. Longitudinal reinforcing steel in reinforced concrete (RC) elements may undergo large tension and compression strain reversal that lead to buckling of steel bars. The buckling is a phenomena associated to bar slenderness values that typically may cause second order effects.
In non-linear finite element analysis (NLFEA) rebar can be modelled using beam elements with geometrical and mechanical non linearity or using different approaches like fibre models or smeared models in which the steel behaviour is represented by constitutive model derived on the average behaviour of bare bar experimentally calibrated. In this field it is located the PARC_CL 2.1 smeared crack model implemented at the University of Parma in UMAT.for user subroutine of Abaqus software. Two different models for the buckling effect have been implemented. The first one is the Monti-Nuti model, able to take into account the softening of steel in compression in case of bar slenderness values ranging from 5 to 11. The second one is the Kashani model, for slenderness values up to 30.
In this paper, NLFEA of a RC column is provided to highlight the differences of the response prediction between the two models
Numerical prediction of multi-storey reinforced concrete walls by static and dynamic analysis using the PARC_CL 2.0 crack model
No full textPhase 2 of the CASH benchmark was dedicated to the response prediction of multi-storey reinforced
concrete (RC) walls used as seismic resisting members in nuclear power plants. Nonlinear static and
dynamic analyses have been carried out to check the reliability of non-linear finite element analysis
(NLFEA) to assess the seismic capacity of reinforced concrete walls. Authors attended the benchmark
by modelling RC walls using multi-layered shell elements and by adopting a self implemented crack
model. The paper describes modelling strategies and some critical issues of the Eurocode 8 prescriptions for the shear demand and shear capacity evaluation of multi-storey RC wall
A crack model for corroded reinforced concrete elements subject to cyclic loading
No full textCorrosion of embedded reinforcement is the main cause of deterioration of existing reinforced concrete infrastructure. Corrosion can significantly affect the seismic response and failure mode of reinforced concrete elements, causing premature concrete crushing, size reduction of reinforcement, degradation of mechanical properties of steel and concrete, and degradation and breaking of stirrups. The latter effects trigger inelastic buckling of the longitudinal reinforcement. In this paper, a non-linear finite-element approach, based on multi-layer shell elements and a crack model, is presented. The fixed crack model was developed at the University of Parma (Italy) and is implemented as a subroutine in standard finite-element software. The model incorporates cyclic constitutive laws for steel able to account for buckling of longitudinal rebars and the effects of corrosion. The effectiveness of the proposed model is validated through comparison with experimental data available in the literature. Finally, the capability of the proposed shell modelling to implicitly consider axial force, shear force and bending moment interaction is discussed and comparisons with analytical model and non-linear finite-element analysis results are provided
Eidetics of Social Acts vs. Eidetics of Acts of Meaning: Different Wholes-Parts Connections and Qualitative Degrees of Existence
No full textI argue that Reinach’s social acts are a new type of acts with respect to Husserl’s acts of meaning. I focus on the eidetic structure of both acts of meaning and social acts and identify the wholes-parts connections that constitute them. I point out that acts of meaning and social acts have a similar but not identical wholes-parts structure. Social acts are a new kind of wholes, irreducible to the wholes-acts of meaning that are “mental linguistic acts,” which may occur only internally in the mind of their agent without addressing another person, and that also belong, according to Husserl, to the category of “objectifying acts”. Indeed, social acts are constituted by further and new parts, with respect to those of acts of meaning: the making-known of the act to an addressee, the turning toward an addressee and their interpellation, the tendency to be perceived by the addressee, the internal experience that grounds the social act, the normative efficacy of the social act. These parts make the sociality of the social acts and characterize their intentionality as essentially social. At the same time, I show that Reinach’s eidetics of social acts provides a qualitative ontological account that distinguishes different degrees of existence and raises the question of the “good life” of social acts. I argue for these issues by referring to Husserl’s theory of parts and wholes and account of acts of meaning (1901), to Reinach’s account of social acts (1913), and to Scheler’s idea of the reciprocity of social acts (1913-1926)
Il fenomeno del buckling implementato nel modello fessurativo PARC_CL 2.1
Full text linkGli edifici esistenti in calcestruzzo armato, progettati prima delle attuali normative sismiche, presentano solitamente un’armatura traversale ridotta o assente che causa un cattivo confinamento dell’armatura longitudinale. Durante il sisma le armature longitudinali possono essere sottoposte ad elevate deformazioni che possono indurre lo svergolamento (“buckling”). Si rende dunque necessario l’utilizzo di un modello costitutivo per l’acciaio capace di simulare realisticamente il fenomeno del buckling. I modello analizzati nel presente lavoro sono quello formulati da Monti-Nuti e da Kashani implementati nel modello fessurativo PARC_CL 2.1. Sono stati quindi analizzati elementi in calcestruzzo armato sottoposti a carichi ciclici con caratteristiche geometriche e meccaniche tipi-che degli edifici costruiti negli anni ’70 (pre normativa sismica), simulandone il comportamento con entrambi i modelli proposti.Reinforced concrete (RC) structures, designed and built before the modern seismic codes, typically present an un-derestimated transversal reinforcement, that causes a bad confinement for the longitudinal rebars. During earthquake, longitudinal reinforcement could be subjected to high deformations inducing buckling. It is therefore necessary using a constitutive model able to realistically simulate the buckling phenomenon. In the present work, the Monti-Nuti model and the Kashani model has been ana-lyzed and implemented in the PARC_CL 2.1 crack model. Then, RC elements subjected to cyclic loads with mechanical and geo-metrical characteristics typical of 70’s buildings in Italy (before seismic codes) have been analyzed with the two proposed models.
Pushover analysis of reinforced concrete framed structures: comparison between response obtained using beam or multi-layered shell elements
No full textIn the context of the seismic vulnerability assessment of existing reinforced concrete buildings, the load-carrying capacity of structures is strongly affected by steel and concrete mechanical properties and construction details. In this work, the institute “A. De Gasperi – R. Battaglia”, located in Norcia, is chosen as case study. Two different modelling strategies have been adopted by using beam elements or multi-layered shell elements for the structural schematization. The non-linear behavior and the ductile or brittle failure mode of shell elements are evaluated using PARC_CL 2.0 crack model, implemented as user subroutine in Abaqus Code. The non-linear ductile behavior of beam elements is evaluated using, at each integration point, the moment/curvature and the axial force/strain relationships which are uncoupled. Brittle failure mode in columns, beams and beam-to-column joints are calculated using post-processing procedures based on analytical formulations provided by Italian NCT 2018 and Eurocode 8 Standard Code. The main scope of this paper is thus the evaluation of the structural response of the case study by using nonlinear finite element analyses, highlighting the benefits of using beam or shell element modelin
The PARC_CL 2.1 crack model for reinforced concrete elements subjected to corrosion and long-term effects.
No full textDuring the service life, existing structures may suffer a combination of time-dependent effects, such as creep,
shrinkage and reinforcement corrosion. The corrosion deterioration can significantly affect the durability of
reinforced concrete (RC) elements causing premature concrete crushing, size reduction of reinforcement
cross-section, degradation of mechanical properties of steel and concrete, and stirrups rupture. Furthermore,
to ensure adequate safety and serviceability throughout the life of the structure, the prediction of long-term
strains, due to creep and shrinkage, is important. Creep and shrinkage have a considerable impact on the
performance of RC structures, affecting stress and strain distribution, increasing deflections and crack width.
For this reason, a nonlinear finite element approach, based on multi-layer shell elements and PARC_CL
2.0 crack model is presented in this paper. The PARC_CL 2.1 model is a fixed crack model developed at the
University of Parma and implemented in a FORTRAN subroutine UMAT for for ABAQUS that incorporates
cyclic constitutive laws of materials and the evolution of corrosion, shrinkage and creep over the time. The
effectiveness of the proposed model is validated through comparison with experimental data available in
literature
A Note on Supersymmetry and Stochastic Differential Equations
No full textWe obtain a dimensional reduction result for the law of a class of stochastic differential equations using a supersymmetric representation first introduced by Parisi and Sourlas
Some Recent Developments on Lie Symmetry Analysis of Stochastic Differential Equations
No full textWe present a brief review of recent progresses on Lie symmetry analysis of stochastic differential equations (SDEs). In particular, we consider some general definitions of symmetries for Brownian motion driven SDEs, as well as of weak and gauge symmetries of SDEs driven by discrete-time semimartingales. Some applications of Lie symmetry analysis to reduction and reconstruction of SDEs, Kolmogorov equation and numerical schemes for SDEs are discussed. Studies on random symmetries of SDEs, as well as extension of Noether theorem on invariants to stochastic systems and the finding of finite-dimensional solutions to SPDEs are also briefly reviewed
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