624.012.36

reinforced concrete beams, biaxially compressed concrete, experimental studies, bearing capacity, deformations.

The article substantiates the relevance and necessity of further experimental research of reinforced concrete structures under biaxial compression. First, this concerns slab monolithic structures of floors with bidirectional arrangement of inserts and slab monolithic flat foundations. To solve the problem, three main types of test specimens were designed, manufactured and tested, which have a cross arrangement of beams. In addition, four types of conventional beams were manufactured, which consist of cross beams, and cubes and prisms to determine the actual deformation and strength characteristics of concrete. In the middle part of the beams in the zone of pure bending, only the lower working reinforcement is provided, which is adopted according to the results of verification calculations so that the destruction occurs in compressed concrete. Outside the zone of pure bending, the upper and transverse reinforcement are provided to prevent destruction in inclined sections. The geometric dimensions of the test specimens are adopted taking into account the design of the existing force stand and the technical characteristics of the test equipment. The linear and cross-section test specimens were loaded with two and four symmetrically located concentrated forces, respectively, using hydraulic jacks and force-distributing traverses. The loads were monitored by tared circular dynamometers mounted on supports. The experimental studies have shown that in the area of the cross-section of the beams, concrete is strengthened due to biaxial compression. The bearing capacity of the test specimens of linear beams compared to their bearing capacity in the composition of crossbeams is lower by 10.6-12.5%. An important parameter of the stress-strain state of compressed concrete is deformations, which are functionally related to its strength. The deformations of the test specimens of concrete, measured directly on the upper face in the area of the cross-section of the beams, are lower than ein the neighboring areas by an average of 19.8%, which confirms the effect of concrete strengthening. Threfore, biaxial compression affects the deformation characteristics of concrete and its strength.

1. Mel’nyk I. V. (2016) Stress-strain state of the fragments of armored monolithic floors with tubular inserts. Materials Science, vol. 52, no. 2, pp. 269–279. Available at: https://doi.org/10.1007/s11003-016-9954-9.
2. Mel’nyk I. V. (2019) Stiffness of monolithic reinforced-concrete slab structures. Materials Science, vol. 55, no. 3, pp. 367–373. Available at: https://doi.org/10.1007/s11003-019-00311-1.
3. Bambura A., Mel’nyk I., Bilozir V., Sorokhtey V., Prystavskyi T., Partuta V. (2020) The stressed-deformed state of slab reinforcedconcrete hollow structures considering the biaxial compression of concrete. Eastern-Europ. J. of Enterprise Technol, vol. 1, no. 7 (103), pp. 34–42. Available at: https://doi. org/10.15587/1729-4061.2020.194145.
4. Dovbenko T., Dvorkin L., Homon S. (2023) Structure formation and performance properties of modified gypsum and phosphogypsum binders. Scientific Journal of Ternopil National Technical University, vol 110, no. 2, pp. 125–135.
5. Kolisnyk M., Iasni V., Homon S. (2022) Modeling of the deformation impact of the main structure framework on the stress and strain state of its individual parts. Scientific Journal of Ternopil National Technical University, vol. 105, no. 1, pp. 141–147.
6. Charpin L., Pape Y.-L., Coustabeau É., Toppani É., Heinfling G., Bellego C.-L., Masson B., Montalvo J., Courtois A., Sanahuja J., and Reviron N. (2018) A 12 year EDF study of concrete creep under uniaxial and biaxial loading. Cement and Concrete Research, vol. 103, pp. 140–159. Available at: https://doi.org/10.10 16/j.cemconres.2017.10.009.
7. Matthias Quast and Manfred Curbach (2017) Concrete under biaxial dynamic compressive loading. Procedia Eng., vol. 210, pp. 24–31. Available at: https://doi.org/10.1016/j.proeng.2017.11.044.
8. Rong C., Shi Q., Zhang T. and Zhao H. (2018) New failure criterion models for concrete under multiaxial stress in compression. Construction and Building Mater., vol. 161, pp. 432–441. Available at: https://doi. org/10.1016/j.conbuildmat.2017.11.106.
9. Deng Z., Sheng J. and Wang Y. (2019) Strength and constitutive model of recycled concrete under biaxial compression. KSCE J. of Civil Eng., vol. 23, is. 2, pp. 699–710. Available at  https://doi.org/10.1007/ s12205-018-0575-8.
10. Gafoor A. H. M. A. and Dinkler D. (2022) Modeling damage behavior of concrete subjected to cyclic and multiaxial loading conditions. Structural Concrete, vol. 23, is. 4, pp. 2322–2336. Available at: https://doi. org/10.1002/suco.202100109.
11. Quast M. and Curbach M. (2015). Behaviour of concrete under biaxial dynamic loading. Proc. of Fifth Int. Workshop on Perfomance. Protection and Strengthening of Structures under Extreme Loading, pp. 3–10.
12. Wang H., Sun H., Shen J. and W. Fan (2021) Experimental study on dynamic biaxial tension-compression properties of hydraulic concrete. Australian J. of Civil Eng., vol. 19, is. 1, pp. 98–106. Available at: https://doi.org/10.1080/14488353.2020.1813924.
13. Zhou J., Pan J., Zhang L., Zhao J. and Li Z. (2020) Experimental study on mechanical behavior of high-strenght high-performance concrete under biaxial loading. Construction and Building Mater., vol. 258, no. 2, pp. 165–178. Available at: https://doi.org/10.1016/j.conbuildmat.2020.119681.
14. Pavlikov A., Kosior-Kazberuk M., Harkava O. Experimental testing results of reinforced concrete beams under biaxial bending. International Journal of Engineering & Technology, vol. 7, issue 3, pp. 299–305. Doi: https://doi.org/10.14419/ijet.v7i3.2.14423.
15. Harkava O. V., Pavlikov A. M. (2023) Determination of the bearing capacity of biaxially bended beams based on the design strength of reinforced concrete. IOP Conference Series: Earth and Environmental Science, vol. 1254. Doi: 10.1088/1755-1315/1254/1/012073.
16. Gang H., Kwak H.-G. (2017) A strain rate dependent orthotropic concrete material model. International Journal of Impact Engineering, vol. 103, pp, 211–224. Doi: https://doi.org/10.1016/j.ijimpeng.2017.01.027.
17. Quast M., Curbach M. (2017) Concrete under biaxial dynamic compressive loading. Procedia Engineering, vol. 210, pp. 24–31. Doi: https://doi.org/10.1016/j.proeng.2017.11.044.
18. Deng Z., Sheng J., Wang Y. (2019) Strength and Constitutive Model of Recycled Concrete under Biaxial Compression. KSCE Journal of Civil Engineering, vol. 23, issue 2, pp. 699–710. Available at: https://doi.org/ 10.1007/s12205-018-0575-8. (103).
19. Charpin L., Pape Y., Coustabeau É., Toppani É., Heinfling G., Bellego C., Masson B., Montalvo J., Courtois A., Sanahuja J., Reviron N. (2018) A 12 year EDF study of concrete creep under uniaxial and biaxial loading. Cement and Concrete Research, vol. 103, pp. 140–159. Available at: https://doi.org/10.1016/j.cemconres. 2017.10.009.

1. Mel’nyk I. V. (2016) Stress-strain state of the fragments of armored monolithic floors with tubular inserts. Materials Science, vol. 52, no. 2, pp. 269–279. Available at: https://doi.org/10.1007/s11003-016-9954-9.
2. Mel’nyk I. V. (2019) Stiffness of monolithic reinforced-concrete slab structures. Materials Science, vol. 55, no. 3, pp. 367–373. Available at: https://doi.org/10.1007/s11003-019-00311-1.
3. Bambura A., Mel’nyk I., Bilozir V., Sorokhtey V., Prystavskyi T., Partuta V. (2020) The stressed-deformed state of slab reinforcedconcrete hollow structures considering the biaxial compression of concrete. Eastern-Europ. J. of Enterprise Technol, vol. 1, no. 7 (103), pp. 34–42. Available at: https://doi. org/10.15587/1729-4061.2020.194145.
4. Dovbenko T., Dvorkin L., Homon S. (2023) Structure formation and performance properties of modified gypsum and phosphogypsum binders. Scientific Journal of Ternopil National Technical University, vol 110, no. 2, pp. 125–135.
5. Kolisnyk M., Iasni V., Homon S. (2022) Modeling of the deformation impact of the main structure framework on the stress and strain state of its individual parts. Scientific Journal of Ternopil National Technical University, vol. 105, no. 1, pp. 141–147.
6. Charpin L., Pape Y.-L., Coustabeau É., Toppani É., Heinfling G., Bellego C.-L., Masson B., Montalvo J., Courtois A., Sanahuja J., and Reviron N. (2018) A 12 year EDF study of concrete creep under uniaxial and biaxial loading. Cement and Concrete Research, vol. 103, pp. 140–159. Available at: https://doi.org/10.10 16/j.cemconres.2017.10.009.
7. Matthias Quast and Manfred Curbach (2017) Concrete under biaxial dynamic compressive loading. Procedia Eng., vol. 210, pp. 24–31. Available at: https://doi.org/10.1016/j.proeng.2017.11.044.
8. Rong C., Shi Q., Zhang T. and Zhao H. (2018) New failure criterion models for concrete under multiaxial stress in compression. Construction and Building Mater., vol. 161, pp. 432–441. Available at: https://doi. org/10.1016/j.conbuildmat.2017.11.106.
9. Deng Z., Sheng J. and Wang Y. (2019) Strength and constitutive model of recycled concrete under biaxial compression. KSCE J. of Civil Eng., vol. 23, is. 2, pp. 699–710. Available at  https://doi.org/10.1007/ s12205-018-0575-8.
10. Gafoor A. H. M. A. and Dinkler D. (2022) Modeling damage behavior of concrete subjected to cyclic and multiaxial loading conditions. Structural Concrete, vol. 23, is. 4, pp. 2322–2336. Available at: https://doi. org/10.1002/suco.202100109.
11. Quast M. and Curbach M. (2015). Behaviour of concrete under biaxial dynamic loading. Proc. of Fifth Int. Workshop on Perfomance. Protection and Strengthening of Structures under Extreme Loading, pp. 3–10.
12. Wang H., Sun H., Shen J. and W. Fan (2021) Experimental study on dynamic biaxial tension-compression properties of hydraulic concrete. Australian J. of Civil Eng., vol. 19, is. 1, pp. 98–106. Available at: https://doi.org/10.1080/14488353.2020.1813924.
13. Zhou J., Pan J., Zhang L., Zhao J. and Li Z. (2020) Experimental study on mechanical behavior of high-strenght high-performance concrete under biaxial loading. Construction and Building Mater., vol. 258, no. 2, pp. 165–178. Available at: https://doi.org/10.1016/j.conbuildmat.2020.119681.
14. Pavlikov A., Kosior-Kazberuk M., Harkava O. Experimental testing results of reinforced concrete beams under biaxial bending. International Journal of Engineering & Technology, vol. 7, issue 3, pp. 299–305. Doi: https://doi.org/10.14419/ijet.v7i3.2.14423.
15. Harkava O. V., Pavlikov A. M. (2023) Determination of the bearing capacity of biaxially bended beams based on the design strength of reinforced concrete. IOP Conference Series: Earth and Environmental Science, vol. 1254. Doi: 10.1088/1755-1315/1254/1/012073.
16. Gang H., Kwak H.-G. (2017) A strain rate dependent orthotropic concrete material model. International Journal of Impact Engineering, vol. 103, pp, 211–224. Doi: https://doi.org/10.1016/j.ijimpeng.2017.01.027.
17. Quast M., Curbach M. (2017) Concrete under biaxial dynamic compressive loading. Procedia Engineering, vol. 210, pp. 24–31. Doi: https://doi.org/10.1016/j.proeng.2017.11.044.
18. Deng Z., Sheng J., Wang Y. (2019) Strength and Constitutive Model of Recycled Concrete under Biaxial Compression. KSCE Journal of Civil Engineering, vol. 23, issue 2, pp. 699–710. Available at: https://doi.org/ 10.1007/s12205-018-0575-8. (103).
19. Charpin L., Pape Y., Coustabeau É., Toppani É., Heinfling G., Bellego C., Masson B., Montalvo J., Courtois A., Sanahuja J., Reviron N. (2018) A 12 year EDF study of concrete creep under uniaxial and biaxial loading. Cement and Concrete Research, vol. 103, pp. 140–159. Available at: https://doi.org/10.1016/j.cemconres. 2017.10.009.