Methods for assessing the impact of partial restraint of hollow core slabs in platform joints on the strength of standard slab cross-sections

Introduction. Currently, hollow core slabs are widely used in large-panel construction, including slabs of formwork-free shaping. Structurally, the presence of voids in slabs has both advantages and disadvantages. One of the drawbacks of hollow precast elements in slabs consists in the reduced load-bearing capacity of the support section compared to solid slabs. This issue is most pronounced when considering the effect of partial restraint in the support zone of the slab in platform joints in large-panel buildings. According to the current design standards for large-panel buildings (SP 335.1325800.2017), the strength of support sections under partial restraint depends on the value of the elastoplastic moment, which is determined empirically and requires verification. The value of the support moment under partial restraint also requires verification due to some current theoretical grounds suggesting its underestimation. Therefore, it seems reasonable to analyze existing approaches to calculating the impact of partial restraint of hollow core slabs on the strength of support sections in platform joints in large-panel buildings and, if necessary, to conduct additional experimental and numerical studies on this issue.

Aim. To analyze the current practice of designing nodes of large-panel buildings using hollow-core slabs, as well as the available experimental studies of the bearing capacity of platform joints with various structural solutions.

Materials and methods. The analysis was conducted by reviewing Russian and foreign regulatory and technical documentation, as well as publicly available results of experimental studies.

Results. The authors have systematized the data on existing methodologies for assessing the strength of hollow core slabs in platform joints in large-panel buildings.

Conclusions. The study analyzed existing methodologies for calculating the strength of hollow core slabs considering their partial restraint in platform joints in large-panel buildings. The authors examined methodologies adopted in Russian and foreign regulatory documents, as well as experimental studies on the topic. The analysis indicated that current calculation methods may neglect the main factors affecting the load-bearing capacity of support sections in joints in large-panel buildings and require further development. Additional research aimed at analyzing the stress-strain state of support sections of hollow core slabs with partial restraint in platform joints will be instrumental in developing a refined physical multifactor model of joint behavior and optimizing structural solutions in certain cases.

1. <i>Lisov S.V., Vekker P.I., Petyanin A.A.</i> Design features of large-panel residential buildings with the possibility of open-plan apartments [internet]. In: The University complex as a regional center of education, science and culture: materials of the All-Russian Scientific and Methodological Conference. Orenburg: Orenburg State University; 2018, pp. 291–294. (In Russian). Available at: http://elib.osu.ru/bitstream/123456789/6060/1/291-294.pdf

2. <i>Kramar V.G., et al.</i> Strength and crack resistance of junctions of prestressed hollow panels of formwork molding with walls of buildings. In: Prestressed reinforced concrete structures of buildings and structures: Collection of scientific works. Moscow: NIIZHB; 1985, pp. 23–34. (In Russian).

3. <i>Kramar V.G., Chalkatryan D.A., Kozhukhov I.I.</i> Prestressed hollow panels with mixed reinforcement. Beton i Zhelezobeton = Concrete and Reinforced Concrete. 1986;(1):3–5. (In Russian).

4. SNiP II-21-75. Design standards. Chapter 21. Concrete and reinforced concrete structures. Moscow: Stroiizdat Publ.; 1976. (In Russian).

5. SP 335.1325800.2017. Large-panel construction systems. Design rules [internet]. Moscow; 2017. Available at: https://docs.cntd.ru/document/557350458. (In Russian).

6. SP 63.13330.2018. Concrete and reinforced concrete structures. General provisions (Changes No. 1) [internet]. Available at: https://docs.cntd.ru/document/554403082. (In Russian).

7. Handbook on the design of residential buildings (to SNiP. 2.08.01-85). Issue 3. Constructions of residential buildings. Moscow: Stroiizdat Publ.; 1989. (In Russian).

8. VSN 32-77. Instructions for the design of structures of panel residential buildings. Moscow: Gosgrazhdanstroi Publ.; 1978. (In Russian).

9. Reinforced concrete prestressed floor slabs for bench formwork molding. Cipher 0-453-04.0. Issue 0. Working drawings. Materials for the design and technical requirements. Yekaterinburg: UralNIIproekt RAASN; 2005. (In Russian).

10. Reinforced concrete prestressed floor slabs for bench-type formwork molding. Cipher IZH 01/04-10.0. Issue 0. Materials for design and technical requirements. Kharkiv: Kharkiv State Technical University of Construction and Architecture; 2010. (In Russian).

11. Recommendations for the use of hollow floor slabs manufactured by continuous molding on long stands (supplement to IZH 568-03). Moscow; 2005. (In Russian).

12. Reinforced concrete prestressed floor slabs for bench-free molding according to TU 5842-001-89328839-09. Cipher 0-464-09.A. The calculation and construction of nodes for the support of hollow floor slabs on the walls of buildings made of bricks or small blocks. Issue A. Supplement (recommended). Yekaterinburg: UralNIIproekt RAASN; 2010. (In Russian).

13. Ordinary reinforced concrete slabs, prestressed, prestressed, without formwork, 220 mm high, for floors and coverings of multi-storey residential, public and industrial buildings. Cipher 0-312. Issue 0. Moscow: TSITP Gosstroy of the USSR; 1984. (In Russian).

14. These reinforced concrete multistage structures are designed for the production of equipment “Weiler” (Italy) for hidden and open house, public and industrial buildings. Series B1.041.1-4.10. Issue 3. Minsk: In-t NIPTIS named after Ataeva S.S.

15. Calculation and design of floor discs using formwork molding plates. R 1.03.055.09. Minsk: In-t NIPTIS named after Ataeva S.S.; 2009. (In Russian).

16. Reinforced concrete slabs, prestressed, prestressed, without formwork forming on Vibropress equipment (Russia) for floors and coverings of residential, public and industrial buildings: Series B1.041.1-5.10. Minsk: In-t NIPTIS named after Ataeva S.S. (In Russian).

17. <i>Lazouski A.D.</i> Work features of hollow slabs of formless molding with platform seams. Vestnik of Polotsk State University. Part F. Constructions. Applied Sciences. 2013;(16):45–50. (In Russian).

18. <i>Chik V.M., Shcherbak S.B.</i> Research of the connections of the interface of the plates of the overlapping of the forming-free forming with wall designs. Vestnik of Brest State Technical University. Series: Construction and Architecture. 2020;(1):112–117. (In Russian).

19. EN 1992-1-1 Eurocode 2: Design of concrete structures - Part 1-1: General rules and rules for buildings [internet]. Available at: https://www.phd.eng.br/wp-content/uploads/2015/12/en.1992.1.1.2004.pdf

20. EN 1168-2005+А2:2009. Precast concrete products - Hollow core slabs [internet]. Available at: https://standards.iteh.ai/catalog/standards/cen/676e9746-3a35-45f9-95be-352a20c64568/en-1168-2005a2-2009

21. <i>fib</i> Bulletin 43: Structural connections for precast concrete buildings. Sprint-Digital-Druck, Stuttgar; 2008.

22. PCI Manual for the Design of Hollow Core Slabs and Walls. Third Ed.; 2015. https://doi.org/10.15554/mnl-126-15