EXPERIMENTAL AND NUMERICAL INVESTIGATION ON SHEAR TRANSFER OF CONCRETE BLOCKS STRENGTHENED WITH CFRP SHEETS UNDER TENSILE FORCE

Abstract

Shear strength which is transmitted across a specific shear plane is denoted as shear transfer. Examples of such situations are precast concrete connections, brackets, corbels, members with deep beam where pure or direct shear is more likely to occur, Column footing connections subjected to high shear forces and concrete cast at different ages are other example. This study presents experimental and numerical investigations that concern the behavior of pull-off for normal and high strength concrete specimens strengthened with various configurations of carbon fiber reinforced polymer (CFRP) sheets. Eighteen samples cast and tested according to the study program. The parameters investigated are: the first was the strength of concrete by casting nine of samples as normal strength concrete and nine as high strength concrete. The results have shown that the ultimate strength are increased and the deformations are decreased in case of high strength concrete and reached to 33% larger than that of the normal concrete. The second parameter is the ratio of reinforcement crossing the shear plane. The results have shown that the reinforcement increases the ultimate strength when compared with blocks without reinforcement, which reached to 22% in case of normal concrete reinforced by 2∅6mm bars, 30% in case of normal concrete reinforced by 2∅10mm bars, 17% in case of high strength concrete reinforced 2∅6mm bars, and 23% in case of high strength concrete reinforced by 2∅10 mm bars. The third parameter was the CFRP strengthening configuration. The result shows that the strengthening led to increase ultimate strength up to 20% in case of normal concrete strengthened in direction perpendicular to the shear plane, 17% in case of high strength concrete strengthened in direction perpendicular to the shear plane , 33% in case of normal concrete strengthened in direction parallel to the shear plane and 27% in case of high strength concrete strengthened in direction parallel to the shear plane where these comparisons done with same reference specimens. Also finite elements analysis a three dimensional with eight noded elements to represent concrete have been used together with embedded bar elements to represent the reinforcement. The analysis took into account the nonlinear behavior of concrete in compression, tension and the reduction of the shear modulus due to cracking. A good agreements are issued from FEA with the experimental results with differences at ultimate stages are less than 10%.