Abstract A numerical analysis of fluid-body interaction is performed in this work in order to evaluate the influence of vortex and tornado-like flows on immersed objects. Velocity profile models are adopted to generate vortical flow fields based on time-dependent boundary conditions and a finite element formulation is used for spatial discretization, where eight-node hexahedral elements with one-point integration are adopted. In addition, an arbitrary Lagrangian-Eulerian (ALE) approach is proposed to describe the relative motion between vortex flow and immersed objects. The flow governing equations are discretized using an explicit two-step Taylor-Galerkin scheme and tornado flow fields are simulated using the Rankine Combined Vortex Model (RCVM) and the Vatistas Model. Turbulence modeling is performed using Large Eddy Simulation (LES) with the Smagorinsky’s sub-grid scale model. Problems involving moving and stationary tornadoes interacting with fixed and moving objects are analyzed, where significant aerodynamic forces are observed on the immersed bodies, producing also significant changes in the vortex flow characteristics. fluidbody fluid body tornadolike like timedependent time dependent discretization eightnode eight node onepoint one point addition LagrangianEulerian Lagrangian Eulerian ALE (ALE twostep two step TaylorGalerkin Taylor Galerkin RCVM (RCVM LES (LES Smagorinskys Smagorinsky s subgrid sub grid model analyzed bodies characteristics

Abstract Modeling and simulation of mechanical response of structures, relies on the use of computational models. Therefore, verification and validation procedures are the primary means of assessing accuracy, confidence and credibility in modeling. This paper is concerned with the validation of a three dimensional numerical model based on the finite element method suitable for the dynamic analysis of soil-structure interaction problems. The soil mass, structure, structure's foundation and the appropriate boundary conditions can be represented altogether in a single model by using a direct approach. The theory of porous media of Biot is used to represent the soil mass as a two-phase material which is considered to be fully saturated with water; meanwhile other parts of the system are treated as one-phase materials. Plasticity of the soil mass is the main source of non-linearity in the problem and therefore an iterative-incremental algorithm based on the Newton-Raphson procedure is used to solve the nonlinear equilibrium equations. For discretization in time, the Generalized Newmark-β method is used. The soil is represented by a plasticity-based, effective-stress constitutive model suitable for liquefaction. Validation of the present numerical model is done by comparing analytical and centrifuge test results of soil and soil-pile systems with those results obtained with the present numerical model. A soil-pile-structure interaction problem is also presented in order to shown the potentiality of the numerical tool.

Nesse trabalho, apresenta-se um modelo numérico para a análise não-linear estática e dinâmica de vigas, placas e cascas de concreto reforçado. Sendo assim, procedimentos de análise, baseados na teoria da plasticidade e com monitoramento de fissuração, são desenvolvidos. Elementos finitos de casca degenerada de 9 nós são usados na análise estática, enquanto elementos finitos de 20 nós são considerados para a análise dinâmica. A lei constitutiva do concreto é acoplada a um modelo sensível à velocidade de deformação, para se terem em conta os efeitos produzidos para altas velocidades de deformação. O procedimento de Newmark é adotado para a integração no tempo do sistema não-linear de equações. Considera-se que o aço de reforço está perfeitamente distribuído e aderido ao concreto, sendo esse representado por elementos finitos de membrana. Vários exemplos são solucionados com o presente modelo numérico e os resultados obtidos são conferidos com os resultados de outros autores. Para todos os casos, o caminho de falha, o carregamento de colapso e o mecanismo de falha são reproduzidos com suficiente precisão.

A numerical model using the Finite Element Method (FEM) for the nonlinear static and dynamic analysis of reinforced concrete (RC) beams, plates and shells is presented in this work. For this purpose, computer programs based on plasticity theory and with crack monitoring capabilities are developed. The static analysis of RC shells up to failure load is carried out using 9-node degenerated shell finite elements while 20-node brick finite elements are used for dynamic applications. The elasto-plastic constitutive law for concrete is coupled with a strain-rate sensitive model in order to take into account high loading rate effect when transient loading is intended. The implicit Newmark scheme with predictor and corrector phases is used for time integration of the nonlinear system of equations. In both cases, the steel reinforcement is considered to be smeared and represented by membrane finite elements. Various benchmark examples are solved with the present numerical model and comparisons with other published data are performed. For all examples, the path failure, collapse loads and failure mechanism is reproduced with great accuracy.

An adaptive mesh strategy based on nodal re-allocation is presented in this work. This technique is applied to problems involving compressible flows with strong shocks waves, improving the accuracy and efficiency of the numerical solution. The initial mesh is continuously adapted during the solution process keeping, as much as possible, mesh smoothness and local orthogonality using an unconstrained nonlinear optimization method. The adaptive procedure, which is coupled to an edge-based error estimate aiming to equidistribute the error over the cell edges is the main contribution of this work. The flow is simulated using the Finite Element Method (FEM) with an explicit one-step Taylor-Galerkin scheme, in which an Arbitrary Lagrangean-Eulerian (ALE) description is employed to take into account mesh movement. Finally, to demonstrate the capabilities of the adaptive process, several examples of compressible inviscid flows are presented.

Geometrically nonlinear static and dynamic behaviour of laminate composite shells are analyzed in this work using the Finite Element Method (FEM). Triangular elements with three nodes and six degrees of freedom per node (three displacement and three rotation components) are used. For static analysis the nonlinear equilibrium equations are solved using the Generalized Displacement Control Method (GDCM) while the dynamic solution is performed using the classical Newmark Method with an Updated Lagrangean Formulation (ULF). The system of equations is solved using the Gradient Cojugate Method (GCM) and in nonlinear cases with finite rotations and displacements an iterative-incremental scheme is employed. Numerical examples are presented and compared with results obtained by other authors with different kind of elements and different schemes.

This work presents a geometric nonlinear dynamic analysis of plates and shells using eight-node hexahedral isoparametric elements. The main features of the present formulation are: (a) the element matrices are obtained using reduced integrations with hourglass control; (b) an explicit Taylor-Galerkin scheme is used to carry out the dynamic analysis, solving the corresponding equations of motion in terms of velocity components; (c) the Truesdell stress rate tensor is used; (d) the vector processor facilities existing in modern supercomputers were used. The results obtained are comparable with previous solutions in terms of accuracy and computational performance.