Eduardo Nobre Lages

Nonlinear Finite Element Analysis using an Object-Oriented Philosophy – Application to Beam Elements and to the Cosserat Continuum

Abstract.An Object-Oriented Programming (OOP) frame-work is presented for solving nonlinear structural mechanics problems by means of the Finite Element Method (FEM). Emphasis is placed on engineering applications (geometrically nonlinear beam model, and elastoplastic Cosserat continuum), and OOP is employed as an effective tool, which plays an important role in the FEM treatment of such applications. The implementation is based on computational abstractions of both mathematical and physical concepts associated to structural mechanics problems involving geometrical and material nonlinearities. The overall class organization for nonlinear mechanics modeling is discussed in detail. All the analyses rely on a generic control class where several classical and modern nonlinear solution schemes are available. Examples which explore, demonstrate and validate the main features of the overall computational system are presented and discussed.

A Unified Library of Nonlinear Solution Schemes

1 A Unified Library of Nonlinear Solution Schemes Sofie E. Leon1, Glaucio H. Paulino1, Anderson Pereira2, Ivan F. M. Menezes2, Eduardo N. Lages2 1 Civil and Environmental Engineering Department, University of Illinois, Urbana, IL, USA 2 Group of Technology in Computer Graphics, Pontifical Catholic University ,Rio de Janeiro, RJ, Brazil 3 Center of Technology, Federal University of Alagoas, Maceio, Alagoas, Brazil

An adaptive time integration strategy based on displacement history curvature

SUMMARY This work introduces a time-adaptive strategy that uses a refinement estimator on the basis of the first Frenet curvature. In dynamics, a time-adaptive strategy is a mechanism that interactively proposes changes to the time step used in iterative methods of solution. These changes aim to improve the relation between quality of response and computational cost. The method here proposed is suitable for a variety of numerical time integration problems, for example, in the study of bodies subjected to dynamical loads. The motion equation in its space-discrete form is used as reference to derive the formulation presented in this paper. Our method is contrasted with other ones based on local error estimator and apparent frequencies. We check the performance of our proposal when employed with the central difference, the explicit generalized- α and the Chung-Lee integration methods. The proposed refinement estimator demands low computational resources, being easily applied to several direct integration methods. Copyright

DOOLINES : an object-oriented framework for non-linear static and dynamic analyses of offshore lines

We present an object-oriented framework, named DOOLINES, for non-linear static and dynamic analyses of slender marine structures which often appear in offshore structures employed in the petroleum and gas industries as, among others, flexible risers, steel catenary risers, umbilicals, floating hoses, and mooring lines. DOOLINES allows the rapid development of tailored, modular, reusable and extensible large-size systems, being itself extensible. These properties, along with the ease of use of our framework, are assessed by means of case studies. Code examples are provided.

ESTUDO DA CONVERGÊNCIA DO MÉTODO DOS AUTÔMATOS CELULARES EM PROBLEMAS DA MECÂNICA DAS ESTRUTURAS COM O USO DO MÉTODO DOS ELEMENTOS FINITOS

Structural and solid mechanics problems can show complex global behavior and, in many cases, without an analytical solution. Numerical methods, such as the Finite Element Method (FEM), are traditionally used to study these systems. The Cellular Automata (CA) is a model based on the idea that the microscopic behavior of a system can be reproduced by smaller systems with simpler local rules. As this approach goes from a microscale to a macroscale, this technique enables the study of microscopic effects in macroscopic objects in a natural way. This paper studies the convergence of a hybrid technique of CA and FEM by developing a computational module capable of simulating solid- and structural-mechanics problems. Four update schemes are studied, evaluating the convergence, with different ordinations and degrees of discretization. Keywords: Finite Elements Methods, Cellular Automata, solid and structural mechanics.

Statistical Design of Experiments Applied to the Design of Compliant Vertical Access Risers

This paper applies design of experiments (DOE) methodology to the design of Compliant Vertical Access Risers (CVAR). This relatively new riser configuration is characterized by its differentiated geometry, achieved by the use of syntactic buoyancy at the lower section of the riser and additional weight at its upper section. The characteristic compliance of the CVAR system is obtained by providing an excessive length of pipe and a horizontal offset between the riser top and end connections. Thus, this system provides vertical access to dispersed subsea wells and its compliance can also compensate for vessel motion. CVAR, being vertical access to the wells, brings the advantage of using dry trees, and also allows the completion and workover operations to be performed from the FPU, offering significantly economic and operational benefits to deepwater oil field development. To guarantee such benefits, some operational and structural constraints must be satisfied. The design of the CVAR system is dependent upon several parameters. This study can provide a better understanding about the behavior of the CVAR in terms of its design parameters by the use of the DOE methodology. DOE is a statistical technique that provides an objective measure of how design parameters are correlated and the effective contribution of each at the riser performance. Consideration of the main effects as well as interaction effects coupled with sensitivity analysis is essential for insightful interpretation of model results and effective decision-making. Thus, this study contributes with the design of Compliant Vertical Access Risers as well as with a methodology that can lead to efficient riser design, being a first step in the optimization design process.Copyright