Bond of steel reinforcing bars in self-prestressed hybrid steel fiber reinforced concrete: Fid-Bau Portal

Bond of steel reinforcing bars in self-prestressed hybrid steel fiber reinforced concrete

Chu, S.H. / Unluer, C. / Yoo, D.Y. / Sneed, L. / Kwan, A.K.H.

Highlights • The bond behavior of steel reinforcing bars in hybrid steel fiber reinforced concrete (HSFRC) made with micro and macro steel fibers was investigated. • Without increasing the total fiber volume, the hybrid use of micro and macro steel fibers increased bond strength and initial bond stiffness by up to 31% and 60%. • The bond stress-slip model was extended to hybrid steel fiber reinforced concrete and prediction models for the bond strength and stiffness were developed. • It was proven that the mean crack width of reinforced concrete beam members can be reduced by 20–33% by virtue of the enhanced bond.

Abstract Reinforcing bar bond is of paramount importance for the structural integrity of reinforced concrete and can be enhanced by fiber inclusion and self-prestressing. Previous research has developed bio-inspired self-prestressed fiber reinforced concrete (SP-FRC) utilizing fibers and expansive agent, and multiscale hybrid steel fiber reinforced concrete (HSFRC). In this research, SP-FRC and HSFRC were combined to develop bio-inspired self-prestressed hybrid steel fiber reinforced concrete (SP-HSFRC) in which the bond of steel reinforcing bars was studied experimentally by pull-out tests. From the bond-slip curves, various bond parameters, namely, bond strength, slip at peak bond stress, initial bond stiffness, and secant bond stiffness, were determined and correlated to a hybrid fiber factor to establish analytical models for design calculations. Then, a new bond model that yields finite initial bond stiffness for more realistic bond-slip analysis than the Model Code 2010 was extended to SP-HSFRC, as evidenced by good agreement between the predicted and experimental bond-slip curves. Lastly, the beneficial effect of the improved bond in crack control of steel bar reinforced HSFRC was rigorously proved.