Experimental and theoretical study on the flexural capacity of high-strength concrete beams reinforced with BFRP bars and steel fiber

In order to investigate the influences of depth of steel fiber reinforced concrete layer, steel fiber volume fraction and ratio of basalt fiber reinforced polymer(BFRP) bars on flexural capacity of high-strength concrete beams reinforced with BFRP bars and steel fiber, 11 specimens were cast and tested. The results indicate that there are 3 failure modes of high-strength concrete beams reinforced with BFRP bars and steel fiber:concrete crush, BFRP bars rupture and balance failure. The steel fiber reinforced concrete layer and steel fiber volume fraction have various influences on flexural capacity of specimens. When the BFRP reinforcement ratio is 0.77%, with the addition of steel fiber (the volume fraction was 1.0%), the flexural capacity can be increased by 22.7%; for the specimen with steel fiber volume fraction of 1.0% and steel fiber reinforced concrete layer of 0.57 times of the total depth of beam, the flexural capacity is 86.7% of that of the fully steel fiber reinforced specimen. Increasing BFRP reinforcement ratio is an effective way to improve the flexural capacity of BFRP bar and steel fiber reinforced beams, the flexural capacity of the specimen with BFRP reinforcement ratio of 1.65% is 39.4% higher than that of the specimen with BFRP reinforcement ratio of 0.56%. Based on the experimental and theoretical analysis, a calculating method, which can be used for evaluating the failure mode and flexural capacity of high-strength concrete beams reinforced with BFRP bars and steel fiber, was proposed. The calculated values have good agreement with test results.