- BUILDING STRUCTURES, BUILDINGS AND FACILITIES
- Taking into Account the Decrease in Strength of External Layers of Concrete when Calculating Reinforced Concrete Columns by Normal Cross-Sections
- UDC 624.012.45.075.23

**Dmitry V. KUZEVANOV**, e-mail: kuzevanovd@gmail.com

JSC Research of Construction, NIIZHB named after A. A. Gvozdev, 2-ya Institutskaya ul., 6, Moscow 109428, Russian Federation

**Abstract**. The problem of calculation of reinforced concrete columns with non-uniform concrete strength over the cross-section is considered. Cases and conditions when such heterogeneity arises are shown. An approach to the account of this phenomenon, when controlling the strength of high-strength concrete by introducing a correction factor for the transition from surface strength to strength in the depth of the structure, is presented. The necessity of taking into account such heterogeneity not only when controlling the strength of concrete but when calculating is substantiated. An assessment of correctness of calculations of bearing capacity of compressed elements, when ignoring the fact of the low strength of external concrete layers, is made. The most "cautious" values of permissible limits of changes in the strength of outer and inner layers of concrete in structures, when there are no significant differences in assessing the bearing capacity of elements, are determined. It is shown that the admissible values of the correction factor can vary depending on the sizes of cross-sections of elements controlled. Ways of adapting the existing calculation methods according to normal cross-sections to account the inhomogeneous strength of concrete in section are proposed. Proposals that account non-uniform concrete strength over the cross-section depending on the value of revealed change in the strength of concrete on the surface and in the depth are formulated for practical application.

**Key words**: high-strength concrete, deformation model, strength control, strength heterogeneity, reinforced concrete columns, calculation by normal cross-sections. - REFERENCES

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