Influence of Reinforcement of Contour High-Strength Reinforcement without Adhesion to Concrete on the Deflections of Monolithic Beams

Excessively large deflections in the center of the slab are one of the most significant drawbacks that prevent the spread of monolithic flat ceilings during spans of more than 7 m. The influence of the application of contour prestressed reinforcement (in a shell) without adhesion to concrete on the deflections of plates with the aspect ratio a/b=1 divided by 2 is considered in the article. In the work presented, the rope laying path in the slab is represented by a part of the parabola passing through the supports, with a height that is equal to the deflection, and the length of the rope's diagonal is equal to the distance between the column axes. Knowing the initial equation of the curved axis of the rope, it is possible to calculate the values of the repulsive forces by integrating this parabola equation and obtain a formula for determining the intensity of the repulsion at any point along the length of the rope. With the help of the finite element method, the deflections of a cell of a flat plate were obtained, where the deflection was taken into account in the form of concentrated forces applied at the nodes of the grid of finite elements along the cell contour. According to the results of the study, it is established that the use of a contour high-strength prestressed reinforcement without adhesion to concrete can reduce the deflections of the slab of overlap up to 15% or more. When prestressing only on one side of the cell, it is possible to advise on the installation of prestressed ropes only on the long side of the slab with a ratio of sides a/b=1.3 or more, because the installation on the short side is not advisable.