Residual fatigue strength assessment of concrete considering tension softening behavior

In this study, the residual strength of plain concrete beams under fatigue loading is assessed. The quasi-brittle nature of the material is considered by including the effect of tension-softening taking place in the fracture process zone. A two step approach is followed. In the first step, the effective critical crack length for unstable fracture to occur is determined by using two different methods, namely a modified LEFM based fatigue crack propagation law and the crack resistance method. In the second step, the moment carrying capacity as a function of increasing effective crack length is obtained in order to assess the residual strength of the member. A parametric study is performed by considering three different softening laws: linear, bilinear and power laws. It is seen that the bilinear softening law matches close to the experimental predictions of other investigators.