dc.description.abstract | This study is mainly to discuss the difference between the seismic performance of the New RC beams with diagonal reinforcement, and that without the diagonal reinforcement. The RC beams with diagonal reinforcement are designed to the New Zealand code NZS3101-2006[2] to prevent the beams in the plastic hinge zone from the failure of the sliding shear crack. Therefore, this study continues to Kai-xiang You [25] research on the hinge relocation design by using T-headed bars. The main conclusion is that the T-headed bars as extra reinforcement can successfully relocate the plastic hinge zone from the column face to a distance away from the face, but the final failure mode of sliding shear occurred.
A experimental work is also carried out in the study. Two cantilever beam specimens, named HB-T0 and HB-T550, with rectangular cross-section 270mm×550mm are produced. #10 and #8 SD690 as the main reinforcement, #3 SD790 as the transverse reinforcement, and design concrete strength f_c^′=60MPa are used. The prototype beam HB-T0 is a 2.0m long cantilever beam having #8-SD690 diagonal reinforcement. The beam HB-T550 is a 2.2m long cantilever beam with hinge relocating 550mm from the column face. The beam arranged #5-SD790 diagonal reinforcement in the potential plastic hinge zone.
The test results show that, due to the configuration of diagonal reinforcement, HB-T0 began to fail after the DR=8%. Compared with the beams without diagonal reinforcement, the beams with diagonal reinforcement presented a better seismic performance. HB-T550 also showed better seismic behavior in comparison with the beams with hinge relocation, but no diagonal reinforcement set up. Therefore, no shear diagonal crack failure or sliding shear failure was founded in HB-T550 at the end of the test. That is, HB-T550 did not produce obvious pinching, compared with the hysteresis loop of the beam having plastic hinge relocation without diagonal reinforcement, so diagonal reinforcement has the benefit of the seismic resistance on preventing the failure of diagonal shear or vertical sliding shear from occurring.
This article also collected the test data of the previous researches. The results showed that NZS 3101 empirical formula for determining the possibility of sliding shear failure is less suitable application than the short-span beams (a/d<2.5) because of their main failure mode occurred in the diagonal strut compression or shear-tension failure. However, NZS3101 empirical formula can be used for the long-span beams (a/d≥2.5), because these beams were subjected to reverse loads to cause the potential sliding shear cracks to happen in the plastic hinge zone. Thus the check of sliding shear failure is suggested to be considered. In practical situations, when the beam is added with diagonal reinforcement, it should be noted whether the reinforcement configuration in the site is feasible. | en_US |