Dynamic decoupling in reinforced concrete columns in structural core shape and applied to bridges

Abstract

Bridges that are designed to transpose large valleys generally show low stiffness to the lateral bending and, therefore, it is not convenient to use the static modeling of the wind actuation. In this context, due to the large volume of concrete required for the molding of the pillars, it is fitting to design them with a cross section composed of thin walls, in order to confer economy, and with one of the faces open and braced by lintels to guarantee greater stiffness to the deformation by bending due to the performance of the shear forces. Such dynamic modeling of the pillars activates bending-torsion and presents stiffness to the structure bending divided into two matrices: [J] and [S]. Due to the structural stiffness not being bonded in a single matrix, Rayleigh´s proportionality in the damping matrix assembly [C] does not apply. Thus, the formulation for such an assembly of [C] is proposed in this paper via the first three vibration modes of the structure. It models, with examples of application, a bridge with a deck backed on three pillars shaped as structural core braced by lintels and of thin-walled sections. Such pillars, with axes referenced in the torsional center of each, are inclined of β in relation to the global referential of the bridge coordinates, in order to apply the decoupling process of the differential equation system that governs the phenomenon and the resulting referential transformations. The vibration modes are verified by modeling with the ANSYS 2019 R1 software academic version.