Fatigue life of reinforced concrete beams under bending strengthened with composite materials

The present paper focuses on the problem of the durability of bent RC beams strengthened with composite materials, subjected to cyclic loading. The theoretical model of determining fatigue life of the cross-section of the bent reinforced concrete beam strengthened with external, non-stressed CFRP strips is presented. The authorʹs own proposal is to introduce the coefficient of the strip position effect on each individual bar and a way of taking into account the energy absorbed by the strengthening. The energy causes a decrease in the velocity of the crack propagation in the rebar, and consequently, an increase in its durability. The theoretical model was verified in the experiments carried out on two series of reinforced concrete beams with different steel and strengthening ratios. For each group of the beams the value of fatigue load was matched to get similar stress in the tension bars.