Flexural Reinforced Concrete Elements, Strengthened with Fibre Reinforced Polymer, Bearing Capacity Evaluation According to Limit Crack Depth

Abstract

The research was made on condition assessment of flexed reinforced concrete structures, strengthened with fibre reinforced polymers, in fracture stage. Universal bearing capacity calculation method based on limit normal section crack depth was proposed. This paper confirms the hypothesis of triangular concrete’s compressive zone chart usage for flexural strength calculation, without tensile concrete above crack evaluation. There is established connection between crack depth and FRP stress­strain, which allows to decide about structures bearing capacity reserve. The calculation results are confirmed with experimental studies of 73 reinforced concrete beams, strengthened with carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) sheets, plates, strips and rods, taken from different researches. Furthermore, recommended limits of strengthening with FRP were proposed.