The influence of steel yielding of main reinforcement on bending capacity of beams strengthened with CFRP strips

This paper describe tests on RC beams strengthened with externally bounded CFRP plates. A total of four PCC beams with rectangular 15×30cm cross section and 300cm clear span were manufactured and tested in four-point flexure with 100cm constant moment region. Low compressive strength of concrete f_ck about 20MPa and middle reinforcement ratio – 0,0075 were used. Different yield strengths of steel, from 360MPa to 1860MPa, were chosen as experimental variables. All the beams were strengthened with one CFRP strip measuring 5×1,2cm. The specimen failed at various load and at various ultimate strains of CFRP strips. It was generally observed that both the moment capacity and the ultimate strains grew with the increase of steel yielding strength. It could be deducted that in many cases reaching the yielding steel strength activates the deboning of FRP strips.