Experimental investigation on shear performance of fiber-reinforced high-strength concrete dry joints

In order to consider the seven parameters including joint types, confining stress levels, fiber lengths, fiber shapes, fiber types, volume ratios of fibers, and reinforcement of key specimens, seventeen pairs of shear key specimens were cast and tested. The effects of the above seven parameters on the shear behavior and shear capacity of fiber reinforced high-strength concrete (FHSC) dry joints were obtained. Analysis of the test results shows that the type of joint has a great influence on the shear behavior of specimens. Compared with HSC specimens, the cracking stress, ultimate stress, and ductility of FHSC specimens were improved. The average cracking stress is increased by 46.4%, and the average ultimate stress is increased by 25.3%, and the average ductility is increased by 30.9%. Within a certain range, the ultimate stresses of FHSC specimens increase with the increases of confining stresses, fiber lengths, and fiber volume ratios. The end-hook steel fibers have a greater effect on the ultimate stresses than the two other types. Then, the calculating formula for the shear capacity of dry joints was summarized. Based on the existing test data, the calculated results of different formulas were compared and analyzed. It was found that the calculated results of the formula suggested by AASHTO agreed best with the test results for single-keyed specimens, while the formulas suggested by Buyukozturk predicted the shear capacity well for multi-keyed specimens. Also, considering the effect of fibers on the concrete strength, a calculating formula for FHSC was proposed based on Mohr's stress circle principle, which was in a good agreement with the test data.