The Experts below are selected from a list of 499248 Experts worldwide ranked by ideXlab platform

Leone Corradi - One of the best experts on this subject based on the ideXlab platform.

  • A triangular finite element for sequential Limit Analysis of shells
    Advances in Engineering Software, 2004
    Co-Authors: Leone Corradi, N. Panzeri
    Abstract:

    The numerical solution of the Limit Analysis problem has experienced a growing interest in recent years. Methods developed in this context can be employed also to obtain indications on the structural response subsequent to collapse, which is required in several situations, such as for shells employed as shock absorbers or energy dissipators. The procedure is known as sequential Limit Analysis and, as its name suggests, is based on a sequence of Limit Analysis solutions referring to progressively updated configurations. In this paper, the Limit Analysis procedure proposed by Capsoni and Corradi [Int. J. Numer. Meth. Eng. 40 (1997) 2063] is employed to this purpose in conjunction with the TRIC shell element developed by Argyris and co-workers [Comp. Meth. Appl. Mech. Eng. 145 (1997) 11], which is modified to some extent to adapt to the rigid-plastic context. Some examples show the effectiveness and the accuracy of the method, which compares well with results obtained from complete, although computationally demanding, incremental elastic-plastic approaches.

  • Limit Analysis of orthotropic plates
    International Journal of Plasticity, 2003
    Co-Authors: Leone Corradi, Pasquale Vena
    Abstract:

    Abstract The Limit Analysis problem for plates in bending is considered. The failure criterion for the material is assumed as orthotropic, with possible non-symmetric strength properties. According to Kirchhoff’s hypothesis, the plate is conceived as a superposition of layers, individually in plane stress situation, and continuity is enforced by means of a kinematic assumption. By exploiting previous results, recently established by the authors, the expression of the dissipation power per unit plate area is defined on this basis and the kinematic (upper bound) theorem of Limit Analysis is cast in a form suitable for numerical solutions. To this purpose, efficient algorithms successfully employed in the isotropic case can be used with minor modifications. The effectiveness of the procedure is demonstrated by solving some homogeneous plate examples. Results permit the assessment of the influence of different aspects, such as the ratio between strengths along the orthotropy directions, the tensile to compressive strength differential and the inclination of the orthotropy axes with respect to the sides. The effects of in-plane edge constraints are also discussed and it appears that they are emphasized considerably by anisotropy. Even if referred to specific cases, some conclusions can be regarded as fairly general.

Pasquale Vena - One of the best experts on this subject based on the ideXlab platform.

  • Limit Analysis of orthotropic plates
    International Journal of Plasticity, 2003
    Co-Authors: Leone Corradi, Pasquale Vena
    Abstract:

    Abstract The Limit Analysis problem for plates in bending is considered. The failure criterion for the material is assumed as orthotropic, with possible non-symmetric strength properties. According to Kirchhoff’s hypothesis, the plate is conceived as a superposition of layers, individually in plane stress situation, and continuity is enforced by means of a kinematic assumption. By exploiting previous results, recently established by the authors, the expression of the dissipation power per unit plate area is defined on this basis and the kinematic (upper bound) theorem of Limit Analysis is cast in a form suitable for numerical solutions. To this purpose, efficient algorithms successfully employed in the isotropic case can be used with minor modifications. The effectiveness of the procedure is demonstrated by solving some homogeneous plate examples. Results permit the assessment of the influence of different aspects, such as the ratio between strengths along the orthotropy directions, the tensile to compressive strength differential and the inclination of the orthotropy axes with respect to the sides. The effects of in-plane edge constraints are also discussed and it appears that they are emphasized considerably by anisotropy. Even if referred to specific cases, some conclusions can be regarded as fairly general.

Nestor Zouain - One of the best experts on this subject based on the ideXlab platform.

  • Quadratic velocity‐linear stress interpolations in Limit Analysis
    International Journal for Numerical Methods in Engineering, 2014
    Co-Authors: Nestor Zouain, Lavinia Borges, Jose Luis Silveira
    Abstract:

    SUMMARY We compare a family of mixed interpolations on triangles with straight edges as applied to Limit Analysis. The aim of this paper is to prove theoretically that the approximate collapse factors obtained with these finite elements always comply with certain inequalities that exist among them. Two of these interpolations are used in Limit Analysis for the first time in this article. The inequalities in the proposition are also demonstrated via numerical applications. To this end, the most frequently used benchmark problems in Limit Analysis are revisited and discussed with respect to the results computed with these finite elements. Copyright © 2014 John Wiley & Sons, Ltd.

  • An adaptive approach to Limit Analysis
    International Journal of Solids and Structures, 2001
    Co-Authors: Lavinia Borges, Nestor Zouain, Cyntia Costa, Raúl A. Feijóo
    Abstract:

    Abstract The main objective of this paper is to propose an adaptive mesh refinement procedure for finite element models in Limit Analysis. We use an `a posteriori' indicator based on the local directional interpolation error and a recovering scheme to compute second derivatives of the finite element solution. The proposed mesh adaptation process gives improved results in localizing regions of rapid or abrupt variations of the variables, whose location is not known a priori. Limit Analysis of bodies in plane strain and plane stress is considered in the applications.

  • An iterative algorithm for Limit Analysis with nonlinear yield functions
    International Journal of Solids and Structures, 1993
    Co-Authors: Nestor Zouain, José Herskovits, Lavinia Borges, Raúl A. Feijóo
    Abstract:

    Abstract A mathematical programming algorithm is proposed for the general Limit Analysis problem. Plastic behavior is described by a set of linear or nonlinear yield functions. Abstract formulations of Limit Analysis are first considered and a Quasi-Newton strategy for solving the optimality conditions is then sketched. The structure of the problem arising from a finite element discretization is taken into account in order that the algorithm should be able to solve large scale problems.

Wei H. Yang - One of the best experts on this subject based on the ideXlab platform.

  • Large deformation of structures by sequential Limit Analysis
    International Journal of Solids and Structures, 1993
    Co-Authors: Wei H. Yang
    Abstract:

    Although most structures are designed to function under small deformation, their large deformation behavior can be used to estimate reliability and safety for survivorship from an accident or a natural disaster. Structures such as buildings, bridges, ships, vehicles and machinery are designed with a safety factor to protect certain assets from the unexpected and unknot elements. The large deformation Analysis provides the rational basis for a safety factor. In this paper, the method of sequential Limit Analysis is used to compute large deformation solutions of truss and frame problems. Differing from the incremental method of plasticity, the Limit Analysis method is numerically stable, more effecient and requires simpler input data. A duality theorem serves as the foundation of an algorithm for computing the complete static and kinematic solutions sim- uhaneously and for establishing their accuracy in each step of a deformation sequence. The phenom- ena encountered in large deformation such as loading-unloading under monotone deformation, bifurcation (more generally, loss of uniqueness) of solutions, and internal contact of structural members are revealed by the sequential Limit Analysis presented in this paper.

Raúl A. Feijóo - One of the best experts on this subject based on the ideXlab platform.

  • An adaptive approach to Limit Analysis
    International Journal of Solids and Structures, 2001
    Co-Authors: Lavinia Borges, Nestor Zouain, Cyntia Costa, Raúl A. Feijóo
    Abstract:

    Abstract The main objective of this paper is to propose an adaptive mesh refinement procedure for finite element models in Limit Analysis. We use an `a posteriori' indicator based on the local directional interpolation error and a recovering scheme to compute second derivatives of the finite element solution. The proposed mesh adaptation process gives improved results in localizing regions of rapid or abrupt variations of the variables, whose location is not known a priori. Limit Analysis of bodies in plane strain and plane stress is considered in the applications.

  • An iterative algorithm for Limit Analysis with nonlinear yield functions
    International Journal of Solids and Structures, 1993
    Co-Authors: Nestor Zouain, José Herskovits, Lavinia Borges, Raúl A. Feijóo
    Abstract:

    Abstract A mathematical programming algorithm is proposed for the general Limit Analysis problem. Plastic behavior is described by a set of linear or nonlinear yield functions. Abstract formulations of Limit Analysis are first considered and a Quasi-Newton strategy for solving the optimality conditions is then sketched. The structure of the problem arising from a finite element discretization is taken into account in order that the algorithm should be able to solve large scale problems.