A New Stress-Field Based Model to Simulate the Multiple Cracking Process in Engineered Cementitious Composites (ECC)

Abstract

Engineered cementitious composites (ECC) are materials exhibiting strain-hardening behavior up to several percent tensile strain with the formation of multiple cracks. The conditions for achieving multiple cracking have been investigated in literature, but issues such as the sequential formation of multiple cracking, the number of cracks formed at a particular stress level (which governs material ductility) and the crack opening at a particular strain (which affects durability) are seldom addressed. In this paper, a new model to simulate the overall stress-strain relation for an ECC member is developed. For a bridging fiber at a certain inclination angle, the fiber stress and the stress transferred to the matrix at various distances from the crack is derived with consideration of slip hardening behavior, snubbing effect at the fiber/matrix interface and fiber rupture. At any applied loading, the matrix stress at any distance from the crack can be obtained by summing up the stress transfer from all the acting fibers. With a stochastic approach to describe the continuous variation of matrix strength along the member, the stress field in the matrix is compared to the distributed matrix strength to determine the positions of new cracks. The strain at a particular stress level, as well as the corresponding number and openings of cracks, can then be obtained. Using this model, the effects of various micro parameters on the ductility and strength of ECC member can be simulated. This provides guidelines for the design of ECC to achieve better mechanical performance.