Application of regression analysis to improve the shear design method for reinforced concrete structures

Introduction. The mechanism of failure of reinforced concrete structures from the action of shear force has been the object of research of Russian and foreign scientists for many decades. This failure mechanism garners significant attention due to its danger — the shear failure is often brittle and sudden. The bearing capacity and the type of failure of reinforced concrete structure within this mechanism depends on a variety of design parameters, which greatly complicates its study. Key parameters influencing load-bearing capacity in shear failure include the strength of concrete, geometric characteristics of the cross-section, span-to-depth ratio, percentage of tensile reinforcement and the transverse reinforcement intensity. Also, to such parameters can be attributed the energetic size effect which concept is disclosed in the paper. The shear design method, presented in building code SP 63.13330.2018 only indirectly accounts percentage of tensile reinforcement. It also does not consider the energetic size effect, which impacts its accuracy. It is urgent to modify the design method by taking into account these design parameters.

Materials and methods. To obtain the coefficients of the refined design method, the regression analysis performed by the least squares method using the Levenberg – Marquardt algorithm was used.

Results. The paper presents a refined method for shear design of reinforced concrete structures which takes into account the influence of the percentage of tensile reinforcement and energetic size effect. A comparison of the refined design method and the original methodology from SP 63.13330.2018 with the results of laboratory tests of 958 specimens is presented. The specimens are divided into groups according to the values of the design parameters.

Conclusions. The refined design method for shear design of reinforced concrete structures is more accurate than the normative method presented in SP 63.13330.2018. The application of the refined calculation method will allow to correctly assess the load-bearing capacity of inclined sections under the action of shear forces, which in some cases will lead to a reduction in the consumption of transverse reinforcement.

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