Experimental study of the effects of using ultra-high strength reinforcing rebar and UHPFRC on cyclic behavior of reinforced concrete beams

Abstract

Reinforced concrete beams made of ultra-high-performance fiber-reinforced concrete (UHPFRC) are good alternatives to ordinary concrete and reduce the density of reinforcement in the beam, leading to the desired structural behavior. In the present study, the effect of using ultra-high strength reinforcing rebar (UHRR) and UHPFRC on the cyclic behavior of the reinforced concrete beams has been studied experimentally. The current study aims to reduce the amount of UHPFRC and UHRR to achieve a beam with the desired mechanical properties. Nine specimens of real-scale laboratory beams (dimensions of 250 × 200 × 2200 mm) were made and tested by four-point bending with cyclic loading. The empirical study was performed for three volume fractions ratio of UHRR 0.5 %, 1 %, and 1.5 % on three configurations of UHPFRC in the beam: complete UHPFRC beam, beam reinforced with UHPFRC layers at the upper and lower surfaces with thicknesses of 40 mm and beam reinforced with UHPFRC in the longitudinal middle zone of ​​the beam. Parameters of different specimens' cracking patterns, strength capacity, flexural ductility, hysteresis response, energy dissipation, and ultimate strength are compared. The results show that, generally, specimens reinforced with UHPFRC at the upper and lower surfaces of the beam, using less UHPFRC, have better flexural performance than other specimens (even better than complete UHPFRC beam specimen) and are the most desirable condition.