THE INFLUENCE OF STRESS REDISTRIBUTION IN REINFORCED CONCRETE FRAMES ON CRACK RESISTANCE AND STIFFNESS OF THE BEAM

Abstract

Taking into account the redistribution of forces in the calculations of statically indeterminate reinforced concrete structures makes it possible to more reliably assess their bearing capacity, stiffness and crack resistance, as well as to obtain a production and economic effect. At the same time, the determination of the internal forces in the structural elements, taking into account their redistribution, is based on the calculation of the bearing capacity according to the limit states of the first group. The calculation of the crack resistance and stiffness of the frame elements in accordance with the normative documents is performed according to the limit states of the second group, that is, under the action of loads with a characteristic value. But nowadays, the literature does not cover the method of determining the level of redistribution of efforts under the action of characteristic loads.

In the article, on the example of a specific U-shaped frame, the issues of redistribution of forces in it and the method of determining the moment of crack formation and the width of crack opening, as well as the curvature of the bent axis of the bolt are considered, and their values are compared for cases when the frames are calculated as elastic systems and taking into account the redistribution of forces . The calculations proved that no significant difference in the values of these parameters was established, since the criteria of limit states in the deformation technique are the same in all cases.

It has been proven that in frames calculated taking into account the redistribution of forces, along the length of the bolt, the stress-strain state of the cross-sections is more uniform in terms of crack resistance and stiffness than when calculating the frames according to the elastic stage, which is a positive factor.

The above shows that changes in the crack resistance and stiffness of the bolt cannot be an obstacle to the use of the calculation of frames taking into account the redistribution of forces, which has many advantages compared to the calculation of frames as elastic systems.