Fatigue behaviour of fiber reinforced concrete beams

The mechanical behaviour of a fiber-reinforced concrete beam under cyclic bending is examined through a theoretical model based on fracture mechanics. The cracked infinitesimal portion of the beam being considered is subjected to an external bending moment and bridging reactions of the fibers. A rigid-perfectly plastic law is assumed for the reinforcements (whose ultimate reactions correspond to either yielding or slippage), whereas the concrete matrix is supposed to behave in a linear-elastic way. The statically indeterminate bridging forces are computed through congruence conditions, and typical phenomena, such as elastic shake-down and plastic shake-down, are described in terms of applied bending moment against beam cross-section rotation. Then, the Paris law is exploited to analyse the fatigue behaviour of the composite beam up to failure.