Fatigue Behavior of Composite Reinforcement for Concrete Structures

The external bonding of FRP to concrete beam is an effective method in order to increase the structural capacity of such beams. The test under fatigue loading of RC beam reinforced with FRP shows that the strengthening of beam with carbon epoxy composite increases fatigue durability. To design composite reinforcement for a RC beam under fatigue solicitation, one has to determine the mechanical behavior of each material and above all, of the concrete composite interface. We have carried out a set of tests with fatigue solicitation on the concrete/composite interface and a set of tests on composite plate. Those tests set up the fatigue life for several levels of shear stress in the interface and in the composite plate and so allow to assess the maximum fatigue stress curve. The second part of the work is based on the information obtained from the first one to design the reinforcement. The design of the composite reinforcement is determined by a software developed by O. Hamelin and H. Nasseri using a non-linear calculation method. The design method of those reinforcements is based on classical methods used for RC structures, taking into account the slip phenomena at the interface and considering the mechanical behavior of each material. Suitable range of stress for concrete, steel, composite and interface are determined to predict the fatigue life of the reinforced concrete beams. So, the load range for the test on the beam is set up. Safety factors are determined for the structure loading.