COMPARISON OF CALCULATIONS OF THE CROSS-SECTION AREA OF LONGITUDINAL REINFORCEMENT IN COMPRESSED REINFORCED CONCRETE ELEMENTS OF RECTANGULAR CROSS-SECTION ACCORDING TO CURRENT AND PREVIOUS DESIGN STANDARDS

Abstract

Reinforced concrete compressed elements of rectangular section are widely used in buildings and structures. In connection with the introduction of new building codes, it became necessary to develop modern methods for calculating such elements based on a deformation model, taking into account various cases of possible location of the neutral line relative to the cross-section, and to determine the effectiveness of the adopted methods based on a comparison with the calculation results according to previous regulatory documents. The developers of the currently valid regulatory documents proposed to calculate compressed elements based on a deformation model using a full or simplified diagram of concrete deformation, in particular, for elements of rectangular section, two cases of the location of the neutral line relative to the cross-section of the element are considered. The authors proposed a practical method for calculating bending elements of a rectangular profile, while the calculation is performed by the method of successive approximations relative to the height of the compressed section zone, given by the deformation of the extreme compressed fiber of concrete, which corresponds to the maximum bearing capacity of the element. Such calculation prerequisites make it possible to easily determine the required cross-sectional area of the reinforcement, especially when using computer technology. The task is to calculate the cross-sectional area of the longitudinal working reinforcement in a compressed short reinforced concrete element of rectangular cross-section according to current standards and to compare the calculation results with those obtained according to the previous regulatory document. Using the method of successive approximations, we find the value of the height of the compressed concrete zone at which the ratio of the moment from internal forces in the cross-section to the bending moment from the external design load will be as close as possible to unity. Compared the obtained calculation results with the results according to the previous design standards. Cross-sectional area of compressed reinforcement is practically equal to the previously found cross-sectional area found using the deformation model (according to current design standards). The obtained calculation results and the magnitude of the difference with the results according to the previous standards indicate the acceptability of both methods, the advantage of the canceled methodis greater simplicity, especially when using manual calculations, the advantage of the new method is versatility due to the elimination of empiricism, which is an advantage when calculating more complex structures, and the possibility of wide application of computer technology, it is worth noting that for long compressed elements it is necessary to develop an acceptable method for taking into account the influence of flexibility on the bearing capacity of the element.