Flexural behavior and design of under-reinforced concrete beams with BFRP and steel bars

Abstract

This study aims to investigate the flexural behavior of hybrid reinforced concrete beams and study the design methods. Seven concrete beams reinforced with basalt fiber-reinforced polymer (BFRP) bars and steel bars, including six under-reinforced concrete beams and one slightly over-reinforced concrete beam, were constructed and subject to four-point loading. The reinforcement ratio was the main test parameter. The experimental results showed a transition region between the tension and compression failure modes. The upper bound of the reinforcement ratio of this region was determined through a statistical analysis of available data. The under-reinforced concrete beams with BFRP and steel bars yielded large deflections and crack widths, and the deformability factors of these beams were significantly larger than those of over-reinforced concrete beams with hybrid bars reported previously. The American Concrete Institute (ACI) method and Xue’s equation were modified and employed to predict the flexural strength of under-reinforced concrete beams with hybrid bars. The experimental results were utilized to verify the accuracy of existing models to predict the pre-yielding and post-yielding deflections and assess the bond coefficients of the ribbed BFRP bars.