APPROACHES TO CALCULATING REINFORCED CONCRETE SLABS STRENGTENED BY ADDING A CROSS-SECTION OF CONCRETE
DOI:
https://doi.org/10.31650/2786-6696-2026-15-43-50Keywords:
strengthening of reinforced concrete slabs, concrete overlay, interface joint, shear forcesAbstract
The article presents a study of calculation and design methods for strengthening reinforced concrete floor slabs by installing an additional layer of cast-in-place concrete. The relevance of the topic is determined by the need to extend the service life of existing buildings in Ukraine under increased service loads, changes in the functional use of premises, and stricter reliability and safety requirements. A historical analysis of the development of shear-friction theory is carried out - from initial studies to modern fracture-mechanics models that form the normative basis for the design of interface joints in reinforced concrete members. A comparative analysis of analytical expressions for determining the shear capacity of the "old-new concrete" interface is performed in accordance with national (DBN, DSTU) and foreign codes (Eurocode 2, ACI 318, CSA A23), and approaches to accounting for adhesion, friction and mechanical interlock due to surface roughness and shear keys are summarised. Differences in the treatment of the components of shear resistance, which directly affect the amount of steel required for strengthening, the necessary thickness of the additional concrete layer, and the requirements for preparation of the contact surface, are identified. Particular attention is paid to the methodology of numerical modelling of the stress-strain state of strengthened slabs in specialised software packages such as LIRA-SAPR and others, including issues of selecting finite element types and modelling the interface joint. Recommendations are provided on the rational combination of analytical calculations and numerical modelling results in the design of strengthening solutions, and directions for further research aimed at refining design models and improving the efficiency of structural solutions are outlined. The obtained generalizations can be used to substantiate structural solutions for strengthening floor slabs and to improve the reliability of their calculations at various stages of design.
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