Contribuição ao estudo da influência de transversinas no comportamento de sistemas estruturais de pontes

Abstract

The diaphragms in precast concrete girder bridges, although it serves as transverse stiffeners, is an extra cost financially due to the time encumbered in its construction and to the increase of the structure self-weight, which compromises the system’s viability. Their functionality is still contradictory in academic and professional circles. Several authors have different responses to the global behaviour of the structure through their employment. This paper proposes a numerical study, through the finite element method for precast concrete girder bridges and cast-in-place concrete frame bridges. Will vary the amount of intermediate diaphragms, the connection between columns and abutments, as hinge and fixed, and the amount and height of the girders, in order to keep the same level of vertical displacements. The analsys was linear elastic considering columns, beams and precast girders as frame elements, meanwhile slabs, diaphragms and cast-in-place girders as shell elements. The objective was to study the influence of these secondary beams on the structural performance of the bridges. Maximum displacements and forces on the girders and columns were calculated. It was concluded that the inclusion of the intermediate diaphragms presented both positive and negative effects on the distribution forces in the structure, with the largest variations were in normal forces (from -22% to +18,6%), torsion moments (from -27,3% to +16,5%) and horizontal bending moments (from -5,7% to +35%), while parallel displacements to the deck remained almost constant and vertical displacements oscillated due to rise of the structure self-weight and to the rise of stiffness (from -5,9% and +9,6%). Meanwhile the columns suffered reductions in torsional moments (up to -35,2%), but they weren’t prevalent in the design, while the normal forces, bending moments and shear forces didn’t change significantly. Finally, were performed the design and verification of the most requested girder according to the method of Load and Resistance Factor (LRFD), in which the inclusion of the intermediate diaphragms did not contribute significantly.