The effect of the shape of the strain-softening diagram on the bearing capacity of concrete beams

Abstract

The effect of the shape of the strain-softening diagram on the bearing capacity of three-point loaded beams, as calculated by the “fictitious crack model”, is analysed. It is shown that if, at peak load, the openings at the nodes along the fracture zone are smaller than the displacement corresponding to the break-point of the bilinear softening approximation, the maximum load only depends on the slope of its initial linear portion. A “limit break-point” (L) is defined such that bilinear strain-softening diagrams with the same initial slope, and whose break-points are located beyond Point L, will lead to the same maximum load of bent beams. The location of that “limit break-point” as a function of initial slope, beam size and notch depth is also studied; the effect of these variables is explained in terms of notch sensitivity.