Abstract
<jats:p>The study investigates the efficiency of using the bearing capacity surface in the design of reinforced concrete sections. Two methods for constructing it in the N–Mx–My force space are considered: the direct method, based on a parametric sweep of external forces, and the inverse method, in which points of the surface are determined by specifying ultimate strains followed by calculating the corresponding forces. The accuracy of determining the strength utilization coefficient based on the ultimate moment was evaluated on a test load set by comparing it with reference values obtained from direct ultimate state calculations considering the physical nonlinearity of materials. It is shown that both surfaces provide high accuracy, while the direct method produces a smoother surface, and the inverse method allows for a significant reduction in construction time. </jats:p>