Analysis of stress state on plates of concrete bridges with prefabricated beams

Abstract

The calculation methods necessary for dimensioning the concrete bridges, in force in Romania, stipulate a simplified calculus for these ones by taking into account the ratio between plate sides. Thus, the plates supported on their contour, for which the sides ratio is bigger than 2, called long plates or plate bands, the calculation is made considering that significant bending moments could appear only on the direction of the plate short side. The calculus is made for plates with
unitary width assimilated to simply supported beams on the short direction. The maximal bending moment, resulting according to this static scheme, is distributed between the middle of the plate and its support, through coefficients, which take into account the ratio between the beam height and the plate width. The fixing of plate on beams is not a perfect one, but an elastic fixing and the fixing degree of plates on beams is not quantified because the utilized coefficients are considered to cover all possible situations that could occur.
A detailed analysis of stresses acting upon reinforced concrete bridge plates could be achieved either through at site measurements, or using numerical methods of calculation. In order to validate some generally applicable results a great number of measurements on reinforced bridge plates are necessary, which means a special
financial effort. Providing that the finite elements are correctly chosen, the analysis of bridge structures by means of the finite element method offers results much close to reality and the number of structures to be studied is practically unlimited.
The present paper presents the structural analysis of a reinforced concrete bridge with simply supported prefabricated beams made of prestressed concrete and the superstructure plates represent the interest area. The purpose has been to emphasize the maximal stress states in the bridge plates (bending moments on their short direction), dimensioning their characteristic sections, as well as the eventual
appearance of non-characteristic moments in the same section caused by their interaction with beams and cross beams.
Within the study the nonlinear behavior of materials has been taken into consideration by changing the rigidity of elements in plate areas with big stresses in two variants, depending on their magnitude. The analysis using the finite elements method has been verified through the calibration of the utilized model based on the results of previous tests and the final results are presented and debated in detail.