Design of reinforced concrete structures with loop joints of rebar in accordance with State Standard R 70447-2022

Introduction. Currently, loop overlapping joints of reinforcing bars are used in reinforced concrete structures. These types of working rebar connections are most widely used in NPP structures for the construction of slabs and walls made of monolithic reinforced concrete. Loop joints in these structures are used to connect adjacent three-dimensional reinforced blocks that are assembled in advance and installed in the design position before concreting. This type of connection leads to an increase in the manufacturability of construction and installation works, as it significantly reduces labor costs on the construction site when installing reinforcement frames.

The relevance of the development of the standard is due to the fact that the current regulatory framework did not contain detailed instructions on the design requirements for such connections. The absence of these provisions led to significant difficulties in the design of such structures, which led to excessive material and time costs.

The aim of the work is to improve the system of urban planning activities in terms of clarifying and supplementing existing regulatory documents on the design of reinforced concrete structures.

Materials and methods. The development of the standard was carried out taking into account modern requirements, as well as an analysis of the results of recent scientific research. Additionally, the practical domestic experience of using loop joints in the construction of nuclear power facilities was analyzed.

Results. The result of the work is the State Standard R 70447-2022 standard, the provisions of which include new calculation methods, as well as clarifications of existing calculation and design methods, and updated requirements. The draft standard passed public discussions, as well as the necessary expertise and was put into effect.

Conclusions. The standard State Standard R 70447-2022 "Reinforced concrete structures with loop joints of reinforcement for nuclear power facilities" has been developed, the provisions of which will allow developing reliable structural solutions for such structures, including achieving a certain economic effect. At the same time, certain areas for improving the provisions of this standard are noted.

1. State Standard R 70447-2022. Reinforced concrete structures with loop joints of reinforcement for nuclear power facilities. Requirements for design and calculation. (In Russian).

2. Nikolaev V.B., Rubin O.D., Seleznev S.V. Strength calculation and construction of loop joints of prefabricated elements. <i>Beton i Zhelezobeton</i>. 1987, no. 1, pp. 38–40. (In Russian).

3. Nikolaev V.B., Gorbov V.A., Belov A.A., Klimov E.A., Lisichkin S.E. Experimental studies of reinforced concrete structures of nuclear power plants with modified loop joints on large-scale reinforced concrete models of beam type. <i>Safety of energy facilities</i>. 2016, no. 1, pp. 66–81. (In Russian).

4. Avdeev K.V., Mamin A.N., Bobrov V.V., Bammatov A.A., Kvasnikov A.A., Маrtyanov K.V., Pugachev B.A. Testing of Elements of Reinforced Concrete Structures With Looped Joints of Reinforcement. <i>Promyshlennoe i grazhdanskoe stroitel'stvo</i> [Industrial and Civil Engineering], 2023, no. 6, рp. 24–30. (In Russian). https://doi.org/10.33622/0869-7019.2023.06.24-30

5. SP 63.13330.2018. Concrete and reinforced concrete structures. General provisions. Updated version of SNiP 52-01-2003. (In Russian).

6. State Standard 14098-2014. Welded joints of reinforcement and inserts for reinforced concrete structures. Types, constructions and dimensions. (In Russian).

7. State Standard 57997-2017. Welded reinforcing products and inserts, welded joints of reinforcement and inserts for reinforced concrete structures. General specifications. (In Russian).

8. SP 14.13330.2018. Seismic building design code. Updated version of SNiP II-7-81*. (In Russian).

9. Federal norms and rules in the field of the use of atomic energy. NP-031-01. Standards for the design of aseismic nuclear power plants. (In Russian).