Raffaele Casciaro

Università della Calabria | Università della Calabria · Department of Computer Engineering, Modelling, Electronics and Systems (DIMES)

Prima parte delle slides del corso di approfondimento tenuto all'Ordine degli Ingegneri di Cosenza nei giorni 27 e 28 febbraio 2020

Seconda parte delle slides del corso di approfondimento tenuto presso l'Ordine degli Ingegneri di Cosenza nei giorni 27 e 28 febbraio 2020

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

Slides del Corso di Formazione "Introduzione all'analisi nonlineare" tenuto presso l'ordine degli Ingegneri di Genova, gennaio 2019

The classical Eurocode-compliant ultimate limit state (ULS) analysis of reinforced concrete sections is investigated in the paper with the aim of verifying if and how this well-established design procedure can be related to plasticity theory. For this reason, a comparative analysis concerning capacity surfaces of reinforced concrete cross sections,...

Testo della presentazione tenuta in Roma presso l’Ordine degli Ingegneri della Provincia

Using the Melan static theorem and an algorithm based on dual decomposition, a formulation for the shakedown analysis of 3D frames is proposed. An efficient treatment of the load combinations and an accurate and simple definition of the cross-section yield function are employed to increase effectiveness and to make shakedown analysis an affordable...

The analysis of slender structures, characterized by complex buckling and postbuckling phenomena and by a strong imperfection sensitivity, is heavily penalized by the lack of adequate computational tools. Standard incremental iterative approaches are computationally expensive and unaffordable, while FEM implementation of the Koiter method is a conv...

The analysis of slender structures, characterized by complex buckling and postbuckling phenomena and by a strong imperfection sensitivity, is heavily penalized by the lack of adequate computational tools. Standard incremental iterative approaches are computationally expensive and unaffordable, while FEM implementation of the Koiter method is a conv...

The paper deals with geometrically nonlinear finite element analysis of folded-plate and shell structures. A Koiter asymptotic approach is proposed, based on the reuse of a linear element in the nonlinear context through a corotational formulation.The corotational approach represents a simple and effective way to satisfy the basic requirement of Ko...

What we call the implicit corotational method is proposed as a tool to obtain geometrically exact nonlinear models for structural elements, such as beams or shells, undergoing finite rotations and small strains, starting from the basic solutions for the three-dimensional Cauchy continuum used in the corresponding linear modelings. The idea is to us...

In our previous paper the implicit corotational method (ICM) was presented as a general procedure for recovering objective nonlinear models fully reusing the information obtained by the corresponding linear theories. The present work deals with the implementation of the ICM as a numerical tool for the finite element analysis of nonlinear structures...

A new quadrilateral four node membrane finite element based on a mixed Hellinger–Reissner variational formulation is proposed. Displacement and stress interpolations are defined by 12 kinematical DOFs (two displacements and one drilling rotation per node) and 9 stress parameters. The displacement interpolation is obtained as a sum of three contribu...

Such we call Implicit Corotational Method, is proposed as a tool to obtain geo-metrically exact nonlinear models for structural elements, such as beams or shells, undergoing nite rotations and small smooth strains starting from the basic solutions for the 3D Cauchy continuum used in the corresponding linear modelings. The idea is to use a local cor...

The work builds upon previous developments made by the authors in the context of the nonlinear, in-plane analysis of masonry walls. The structural behavior is characterized by phenomena, such as strain localization, damage, and friction, which need to be modeled at fine scales. Fine-scale modeling represents a significant challenge with regards to...

The multilevel modeling and solution approach for plane brick masonry walls proposed in [1] and [2] is extended here to the free vibration analysis. The proposed strategy is based on a convenient iterative-residual scheme particularly appropriate for the cited multilevel strategy. Two different modeling levels of the masonry mechanics are used in...

Finite element asymptotic post-buckling analysis, being based on fourth-order expansions of the strain energy, requires that nonlinear structural modeling be accurate to same order, at least with respect to the rigid motions of the elements. A corotational description is proposed here as a general tool to satisfy this requirement of objectivity, by...

Slides of the invited lecture

The paper describes different computational approaches and solution methodologies that can be used in nonlinear structural analysis, in particular, the so called path–following anal-ysis, the linearized stability analysis, the asymptotic analysis, the imperfection sensitivity analysis and the transient dynamic analysis, for each showing the main pr...

The asymptotic method, based on the implementation of the Koiter's approach to nonlinear instability within a finite element numerical context, represents a powerful tool for the analysis of geometrically nonlinear structures, which is able to provide accurate and reliable results through a fast computational scheme [1]. Because it make use of a fo...

In the present paper, the method proposed in [Casciaro R, Garcea G. An iterative method for shakedown analysis, Comput Methods Appl Mech Eng 2002;191:5761–92] for the shakedown analysis is used for the evaluation of the shakedown safety factor of reinforced concrete 3D frames subjected to a combination of varying loads. The FEM discretization for 3...

This work investigates the possibility of using equivalent continua within a multilevel strategy for the analysis of brick masonry walls, as prototypes for the in-plane behavior of masonry buildings. This strategy, proposed and discussed in detail in Part I of the same paper, lies in an iterative solution scheme which uses two levels, local and glo...

A numerical strategy based on a multilevel approach is presented for the nonlinear analysis of brick masonry walls as in-plane prototypes of large masonry structures. The strategy is based on an iterative scheme which uses two different, local and global, modelings of the masonry mechanics contemporarily. The former is the reference mechanical mode...

The paper presents a four node element for the analysis of 2D continua described by elastic–perfectly plastic von Mises laws. Its formulation is based on the assumed stress approach which has been widely tested in the elastic field. The elastoplastic formulation of the element is obtained by enriching its variational basis with the weak enforcement...

The paper deals with the collapse safety of slender elastic structures subjected to local buckling interaction. Using Koiter's asymptotic approach, the mechanical problem is reduced to the search for all the local minima of an indefinite quadratic form over the unit simplex. An efficient recursive branch-and-cut algorithm is proposed for solving th...

In the present paper, the formulation proposed by Casciaro and Garcea (Comput. Meth. Appl. Mech. Eng., 2002; 191:5761–5792) and applied to the shakedown analysis of plane frames, is extended to the analysis of two-dimensional flat structures in both the cases of plane-stress and plane-strain. The discrete formulation is obtained using a mixed finit...

The paper presents a numerical algorithm, based on Koiter's theory of the elastic stability, for detecting the order of infinitesimal mechanisms, i.e. kinematically indeterminate systems of pin-jointed bars. In cases of one degree of indeterminacy the algorithm improves, in terms of computational simplicity and efficiency, an analogous algorithm pr...

The lectures provide an introduction to the computational treatment of Koiter’s asymptotic strategy for post-buckling analysis of thin elastic structures. The analysis of slender structures characterized by complex buckling and post-buckling phenomena and by a strong imperfection sensitivity, suffers from a lack of adequate computational tools. Sta...

The paper deals with the use of Saint Venànt’s general rod theory for deriving the stiffness matrix for 3D beam elements with general cross-section. The elastic factors of the section are obtained through the numerical solution of the Saint Venànt differential equations. Different discretization strategies have been investigated including FEM and B...

The lectures provide an introduction to the computational treatment of Koiter's asymptotic strategy for post-buckling analysis of thin elastic structures. The analysis of slender structures characterized by complex buckling and post- buckling phenomena and by a strong imperfection sensitivity, suers from a lack of adequate computational tools. Stan...

A fast iterative algorithm is presented for the solution of the nonlinear eigenvalue problem K[¸]v = 0; v 6 = 0; K = K T coming from many ¯elds of computational mechanics , e.g. structural buckling and dynamics. The algorithm, initially introduced in [1], has been extensively used as a basic numerical tool for solving the bifurcation equation comin...

The paper aims to formulate assumed stress finite elements for the analysis of elastoplastic structures. The interpolations of the displacement and stress fields, typical of the elastic version of the mixed elements, is enriched with the FEM representation of the plastic strain field. The formulation of the elastoplastic problem of the element is t...

Sommario. Il lavoro tratta della modellazione numerica di strutture scatolari o par- zialmente intelaiate secondo una strategia multilivello global—local: a livello globale, la strutturae vista come assemblaggio di pannelli interconnessi; a livello locale, cia- scuno pannelloe suddiviso in elementi finiti quadrangolari mediante discretizzazione dis...

Sommario. Il modello numerico descritto permette la realizzazione di un'analisi non lineare di telai spaziali in C.A.. L'approccio seguito ipotizza un comportamento elasto- plastico per l'intera struttura e ne ricostruisce il percorso di equilibrio monitorando il variare degli spostamenti e delle tensioni in funzione degli incrementi di carico, al...

The paper presents a discrete mechanical model for masonry walls based on a Lagrangean description where each brick is described as a rigid body and each mortar joint as an interface element. Constitutive assumptions, characterized by elasticity, damage and friction, are associated to the joints only. A numerical solution strategy, based on a mixed...

Shakedown analysis for elastic–perfect plastic structures is discussed and a fast incremental-iterative solution method is proposed, suitable for the FEM analyses of large structures.The theoretical motivations of the proposed method are discussed in detail and an example of its implementation is described with reference to plane frame analysis.Som...

A path-following non-linear elastic analysis for structures composed of assemblages of flat slender elastic panels is presented. The proposed path-following method employs FEM technology and a kinematical model to analyse these structures using a Koiter asymptotic approach. As a result it is possible to verify the accuracy achieved by the asymptoti...

The paper proposes two quadrilateral finite elements for the analysis of plane elastic problems. The elements are designed to obtain a mechanical response characterized by improved in-plane bending behaviour, a response which is difficult to obtain by the usual compatible elements. The adopted assumed stress approach enables either an easy formulat...

Purpose: ² To show that e®ective and reliable computer codes can be obtained by a coherent ¯nite element implementation of the Koiter's perturbation method. ² To remark that careful attention has to be paid to all the implementation details for avoiding kinematical incoher-ences that can strongly a®ect the results. ² To promove the interest in such...

Progetto MECOM, Programma Operativo Plurifondo 94/99 Misura 4.4 " Ricerca scientifica e tecnologica Sviluppi ed applicazioni della meccanica computazionale nella progettazione strutturale in campo civile ed industriale ". Analisi nonlineare di pannelli murari soggetti a fenomeni di tipo fessurativo G. Formica, R. Casciaro

A finite element for the Koiter perturbation analysis of composite slender panels is presented. The element formulation constitutes the extention to the Mindlin plate model of the High Continuity interpolation already adopted by the authors in previous works. In order to easily avoid any shear locking phenomenon the proposed finite element interpol...

The paper presents two quadrilateral finite elements for the analysis of plane elastic problems. The elements are designed in order to obtain, as it is expected from High Performance elements, very accurate results also with rough meshes. In particular their attitude to model well problems dominated by an in-plane bending response is the main chara...

This paper shows that the FEM implementation of Koiter's asymptotic method [W.T. Koiter, On the stability of elastic equilibrium, 1970, Ph.D. Thesis, Delft, 1945. English transl. NASA TT-F10, 883, 1967, AFFDL-TR70-25] outlined by Casciaro et al. [Finite element asymptotic analysis of slender elastic structures: a simple approach, Int. J. Num. Meth....

The paper describes a finite element multigrid strategy for the solution of plate vibration and buckling problems. The solution procedure combines the residual iteration scheme used in Casciaro R, Aristodemo M. International Conference on Finite Elements Nonlinear Solid and Structural Mechanics, Gelio, Norway, 1977, (main loop) with the adaptive mu...

The arc-length Riks strategy has rapidly become a standard tool for path-following analysis of nonlinear structures due to its theoretical ability to surpass limit points. The aim of this paper is to show that the failures in convergence that are occasionally experienced are not related to proper defects of the algorithm but come from a subtle ‘loc...

This paper aims to show that effective and reliable computer codes can be obtained by a suitable finite element implementation of the Koiter's perturbation method. However, careful attention has to be paid to all the implementation details in order to avoid kinematical inconsitencies that can strongly affect the results.

This paper summarizes a part of the first author's Ph.D. Thesis completely devoted to multimode elastic buckling within an FEM strategy. The theoretical arguments unfold among critical points on radial paths (the unique post-critical paths variationally defined), algebraic characterizations, proposition demonstrations and so on, by aiming to prove...

This paper describes the algorithmic aspects of a multigrid solver based on the adaptive generation of a sequence of discretizing meshes. Non-uniform discretization is obtained by confining finer meshes to progressively smaller subdomains. New meshes are generated through bisection refinement according to a local error indicator. A dynamic data str...

The present paper extends the finite element perturbation approach already presented for pin-jointed and framed structures15 to rectangular thin plates. Koiter's asymptotic strategy is coupled with a High-Continuity finite element discretization of the plate. The consistency of the discrete model is discussed from the kinematical and numerical poin...

An asymptotic method directly derived from Koiter's theory and suitable for the solution of elastic buckling problems and its natural adaptation to a numerical solution by means of a finite element technique are presented here. The order of the extrapolation of the equilibrium equations has been intentionally kept very low because attention has bee...

The buckling and post-buckling analysis of elastic planar frames is considered and the use of geometrically exact beam models is thereby advocated. It is shown that usual technical beam models fail to predict correctly the curvature of the post-buckling curve at bifurcation even for standard problems of elastic stability theory. It is also argued t...

A mixed variational principle for the limit analysis of rigid-perfectly plastic continua is discussed, in which the nonlinear yield condition and the associated flow rule appear through a suitably defined ‘penalty’ function. A mixed finite element discrete formulation is derived and a sequential unconstrained minimization technique is devised, affo...