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 con-stitutive law plays an important role in the multiple cracking behavior of ECC.Therefore,proper control of fiber-bridging 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 pre-diction,new mechanisms of fiber/matrix interactions,specifically fiber two-way debonding and pull-out,matrix micro-spalling,and Cook-Gordon effects were included.This revised model vas 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.
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