Effect of Concrete Type on Flexural Behavior of Concrete Beams Reinforced with HSS Bars

Abstract

High-Strength Steel (HSS) bars can be a promising alternative to commonly used mild steel since they have the potential of making more efficient use of highperformance concrete and reducing the required number and size of the reinforcement. The main shortcomings associated with utilizing HSS bars in concrete beams are related to the cracking behavior of these beams at service load and the possibility of concrete crushing prior to steel yielding. This research investigates the effect of using highstrength concrete, fiber-reinforced concrete and compression reinforcement to enhance the flexural behavior of HSS-RC beams. Twenty four beams singly and doubly reinforced with high-strength steel bars were cast using plain concrete, steel fiber and synthetic fiber-reinforced concrete. In addition, concrete compressive strength of 50 and 80 MPa were used in the investigation. Four-point loading flexure tests were conducted on all beams. The flexure test results showed that increasing the concrete compressive strength contributes the most to the flexural capacity in steel fiber-reinforced concrete specimens. The concrete compression strain at mid-span's top surface of steel fiber-reinforced specimens reached up to 0.0039 prior to ultimate loading which, in turn, enhanced the flexural capacity. Results also indicated that highest curvature ductility was achieved by synthetic fiber-reinforced concrete beams with f'c = 80 MPa. The deep propagation of cracks was noticeably restrained at service and steel yielding load in fiber-reinforced specimens. In addition, the applicability of ACI ITG-6R-10 recommendations was evaluated using the results of plain concrete specimens and then extended to cover fiber-reinforced concrete beams. A nonlinear finite element model was developed and verified to evaluate the effect of utilizing different reinforcement ratios on the flexural behavior of the HSS-bar reinforced concrete beams.