Numerical insights on quasi-static behaviors of UHPC-NC composite members by a phase-field approach enhanced with a cohesive-frictional interface model

The risk of cracking/debonding of UHPC-NC composite members, either for repairing/strengthening or newly-built structures, is an issue of great concern by the engineering community. Distinct failure modes are continuously reported in the literature and among them, the complex interactions between matrix (UHPC and NC) cracking and interfacial debonding play a vital role. From modeling aspects, the progressive damage analysis of UHPC-NC composite members is a rather challenging task, especially when complicated cracking scenarios arise. To address this shortfall, this work proposes a novel numerical framework for UHPC-NC members by combining: (i) a nonlocal damage model based on the phase-field approach for matrix cracking of quasi-brittle materials, and (ii) a coupled cohesive-friction model for debonding of UHPC-NC interface. Variational formalization of the method provides a simple basis for the finite element implementation and complex cracking tracking procedures are circumvented. The strengths of the model are explored through numerical investigations of several quasi-static behaviors of UHPC-NC composite members. Their damage evolutions and failure patterns are accurately captured by the model. For the sake of promoting relevant research, the source codes are disclosed to potential users.