Cyclic bond behavior and bond stress-slip constitutive model of rebar embedded in hybrid fiber reinforced strain-hardening cementitious composites

In this study, direct pullout tests were conducted to illustrate the influences of fiber types (polyethylene (PE) fiber, steel (ST) fiber and hybrid PE/ST fiber), rebar diameter (20 mm, 25 mm, 32 mm), matrix strength (50 MPa and 70 MPa), and loading procedure (monotonic and cyclic loading) on the bonding performance between rebar and strain-hardening cementitious composites (SHCC). The effects of design parameters on bond behavior under monotonic loading, as well as degradation laws of bond strength, bond stiffness, and energy dissipation capacity under cyclic loading are discussed in detail. Experimental results indicate the synergic effect of hybrid fiber is beneficial to crack arrest, bond strength, and bond strength and bond stiffness retention. Compared with those under monotonic loading, SHCC specimens under cyclic loading exhibit similar ascending behavior while an obvious performance degradation at descending. Additionally, ST fiber behaved more effectively than PE fiber in improving the energy dissipation capacity. Furthermore, a cyclic bond stress-slip constitutive model with acceptable accuracy is developed to predict the cyclic bond behavior of rebar embedded in SHCC.