Fiber-Bridging Constitutive Law of Engineered Cementitious Composites

This paper is on modeling and measuring fiber-bridging constitutive law of Engineered Cementitious Composites (ECC), a high performance fiber-reinforced cementitious composite featuring high tensile ductility. Fiber-bridging constitutive law plays an important role in the multiple cracking behavior of ECC. Therefore, proper control of fiberbridging behavior through tailoring material microstructure is the key to successfully designing tensile strain-hardening ECC. In this paper, an analytical fiber-bridging model of ECC which connects material constituent parameters and composite properties, built on a previous simplified version, was proposed. To improve accuracy of crack opening prediction, new mechanisms of fiber/matrix interactions, specifically fiber two-way debonding and pull-out, matrix microspalling, and Cook-Gordon effects were included. This revised model was compared with experimental measurement of fiber-bridging behavior and the validity of the model was confirmed. It is expected that this model will greatly improve ECC design technology in terms of steady-state crack width control, key for structural long-term durability, and in terms of composite tensile properties important for structural safety at ultimate limit state.