Alexandre Luis Braun

Numerical simulation of the wind action on a long-span bridge deck

A numerical model to study the aerodynamic and aeroelastic bridge deck behavior is presented in this paper. The flow around a rigid fixed bridge cross-section, as well as the flow around the same cross-section with torsional motion, are investigated to obtain the aerodynamic coefficients, the Strouhal number and to determine the critical wind speed originating dynamic instability due to flutter. The two-dimensional flow is analyzed employing the pseudo-compressibility approach, with an Arbitrary Lagrangean-Eulerian (ALE) formulation and an explicit two-step Taylor-Galerkin method. The finite element method (FEM) is used for spatial discretization. The structure is considered as a rigid body with elastic restrains for the cross-section rotation and displacement components. The fluid-structure interaction is accomplished applying the compatibility and equilibrium conditions at the fluid-solid interface. The structural dynamic analysis is performed using the classical Newmarks method.

A numerical study on the aerodynamic performance of building cross-sections using corner modifications

A numerical investigation is performed in this work in order to evaluate the aerodynamic performance of building cross-section configurations by using corner modifications. The CAARC tall building model is utilized here as reference geometry, which is reshaped considering chamfered and recessed corners. The numerical scheme adopted in this work is presented and simulations are carried-out to obtain the wind loads on the building structures by means of aerodynamic coefficients as well as the flow field conditions near the model’s location. The explicit two-step Taylor-Galerkin scheme is employed in the context of the finite element method, where eight-node hexahedral finite elements with one-point quadrature are used for spatial discretization. Turbulence is described using the LES methodology, with a dynamic sub-grid scale model. Predictions obtained here are compared with experimental and numerical investigations performed previously. Results show that the use of corner modifications can reduce significantly the aerodynamic forces on the building structures, improve flow conditions near the building locations and increase the Strouhal number, which may have an important influence on aeroelastic effects.