Behavior of earthquake-resistant structure elements using polypropylene fiber and high strength reinforcing bars

Abstract

The use of high strength reinforcing bars has becoming an interesting and cost-efficient option in construction industry recently. However, their use is limited due to their low deformability which might induce a brittle collapse in the structures. Also, longer development length is needed to transfer stress from reinforcing bars to the surrounding concrete. This paper focuses on investigating the influence of fibrous concrete and high-strength reinforcing bars on the behavior of structural elements. Five half-scaled specimens of interior joints using plain or fibrous concrete, reinforced with conventional 420 MPa or high strength reinforcing bar of 520 Mpa were experimentally tested. The two specimens of plain concrete, reinforced longitudinally with 16 mm and 19 mm reinforcing bars are defined as control specimens. The other test specimens were casted with Polypropylene fiber reinforced concrete (PFRC) with 16 mm and 19 mm longitudinal reinforcing bar. Loading protocol of all test specimens is defined according to ACI 374.2. The structure behavior, such as dissipated energy, bond between reinforcing bars and surrounding concrete, and stiffness degradation of the four specimens were evaluated and compared. The results obtained shows that the use of fiber increase the dissipated energy up to 27.5 % compared to specimens with plain concrete. Moreover, the peak strength of PFRC specimens was slightly increased (3% - 7%) compared to that of specimens with plain concrete. Moreover, there is an increase in peak-to-peak stiffness at elastic range loading with the addition of fiber, while no significant difference after the yields of longitudinal reinforcing bars.