Numerical model on the stress field and multiple cracking behavior of Engineered Cementitious Composites (ECC)

Engineered cementitious composites (ECC) are materials exhibiting strain-hardening behavior with the formation of multiple cracks. The conditions for achieving multiple cracking have been investigated in the literature, but the sequential formation of cracks and the crack number/openings at a particular stress/strain level, are seldom studied. In this paper, a numerical model to simulate the overall stress-strain relation for an ECC member is developed. For a bridging fiber, the stress transferred to the matrix at various distances from the crack will be derived with consideration of chemical bond, slip hardening, fiber rupture and other factors. At any applied loading, the matrix stress field near the crack can be computed by summing up the stress transfer from all active fibers. With a new approach to describe the continuous variation of matrix strength along the member, the stress field in the matrix will be compared to the distributed matrix strength to determine the positions of new cracks. The strain at a given stress and the corresponding crack number and openings can then be obtained and the simulated stress-strain curve agrees well with experimental results. Insights from this model can facilitate the design of ECC with good mechanical performance as well as high durability.