Micromechanical modeling of softening behavior in steel fiber reinforced cementitious composites

fracture of cementitious materials is governed by its softening behavior. When steel fibers are incorporated into concrete to improve its toughness, the softening behavior can be predicted in terms of the composite micro-parameters including the properties of fiber, matrix and interface as well as fiber size, length, distribution and volume fraction. In this paper, the bridging force provided by a steel fiber at any arbitrary angle to the crack is first modeled in terms of the micro-parameters. For a given fiber distribution, the averaged crack bridging force is then derived and employed to obtain the composite softening behavior. The model is verified at both the microscopic and macroscopic levels with experimental results from the fiber pull-out test and the four-point beam bending test. With the model, numerical simulations are carried out to study the effect of various parameters on the tensile softening behavior. These simulations can facilitate the choice ofmicro-parameters for the most cost-effective material design. 0 1998 Published by Elsevier Science Ltd. All rights reserved