Features of calculations of normal cross sections of reinforced concrete structures according to SP 63.13330.2018

Abstract

Introduction. SP 63.13330.2018 provides two approaches to calculating the strength of normal cross-sections of reinforced concrete structures: the nonlinear deformation model NDM (general approach) and the method of ultimate forces UFM for simple elements of rectangular, T-shaped and I-shaped sections with reinforcement located at the edges of the element. As far as the authors are aware, no detailed studies have been conducted to compare the results obtained with both approaches.Aim. Conduct researchе to compare the results obtained in the calculations for NDM and UFM, identify the differences, establish their physical cause, evaluate the economic aspects of the problem, and make the necessary recommendations.Materials and methods. Calculations were carried out according to the program "OM SNiP Reinforced Concrete". Studies were performed for three types of structures. The first type included four cross sections of elements under two stress states: bending (T-shaped and rectangular), off-center compression (rectangular and annular). The second type of structures included beams tested at the NIIZHB named after A.A. Gvozdev. The third type is lintels according to State Standard 948-84. In all types of structures, under the action of the same forces, reinforcement was selected according to NDM and UFM.Results. It turned out that the compressed zone of concrete in UFM participates in the resistance of cross sections to acting forces much more effectively than in NDM. This can lead to a significant difference in reinforcement. In one of the cases, the steel consumption in the calculations for UFM turned out to be 78 % less than for NDM. Conclusions. For the considered structures, the calculation of the strength of normal cross sections by UFM turned out to be more effective than by NDM. At the same time, all the necessary regulatory requirements are met. Further research is needed to amend the existing regulations.