Modeling of tension stiffening in reinforced cement composites: Part I. Theoretical modeling

A numerical tension stiffening model based on nonlinear finite difference method is proposed to simulate tensile cracking behavior of fiber and fabric reinforced cementitious composites. Main variables of the model include matrix strength; nonlinear bond-slip interfacial characteristics; slack in fabrics; and mechanical anchorage provided by cross yarn junctions. Parametric studies were conducted to identify the sensitivity of material responses caused by the main variables. It is found that the increase in bond and junction strengths slightly improve the postcrack stiffness of composite tensile stress-strain response while the increase in matrix strength is more effective. The tension stiffening is directly correlated to the interfacial bond and interlock mechanisms that transfer load to the cracked portions of brittle materials. An increase in slack level causes larger tensile strains during early crack evolution but does not change the late-term post-crack stiffness. Numerical simulations successfully explain general tensile behavior and crack evolution process observed in experiments.