Influence of Reinforcement of Reinforced Concrete Beams Subjected to Biaxial Bending on the Position of Their Neutral Axis

In building habits, members that are in a state of biaxial bending are often encountered. For example, reinforced concrete purlins, contour beams, crane beams, reinforced concrete frame elements. Despite the fact that building codes contain recommendations for the calculation of members subjected to biaxial bending, the issue of rational placement of reinforcement in the section remains relevant. The article reviews the work in this scope and concludes that there is insufficient research on the effect of reinforcement on the position of the neutral axis. The importance of the relationships under consideration is due to their direct connection with the load-bearing capacity of members subjected to biaxial bending. The purpose of the research is to determine the influence of the location of the reinforcement in the section and the ratio of its dimensions on the position of the neutral axis in a member subjected to biaxial bending. The authors calculated beams with various options for the location of the reinforcement in the section and analyzed the influence of the location of the reinforcement and the ratio of the dimensions of the reinforced concrete members on the position of the neutral axis. The angle of inclination of the axis and the area of the compressed zone of concrete were chosen as parameters determining the position of the neutral axis. Corresponding relationships were established between the effective depth of the section, the ratio of the beam dimensions and the parameters characterizing the position of the neutral axis. The calculation was carried out in accordance with state-of-the-art-type design regulations on ultimate forces and on a nonlinear deformation model. A comparison of the results obtained by the two methods showed both a general and opposite nature of the change in relationships, which is reflected graphically; numerical disarrangements were also identified due to the accuracy of the calculation, the prerequisites and assumptions underlying them.