Shear performance of prestressed ultra high strength concrete encased steel beams

Due to the high compressive strength and durability properties of ultra high strength concrete, prestressed ultra high strength concrete beam was used extensively in bridge engineering, but it possessed obvious brittle behavior. Encasing structural steel into it was a good way for alleviating the problem of brittleness. The purpose of this study was to investigate shear performance of prestressed ultra high strength concrete encased steel beams. A total of fifteen prestressed ultra high strength concrete encased steel beams and seven prestressed ultra high strength concrete beams were tested to shear failure under simply supported three-point loading conditions. The primary variables of this investigation included the presence or not of structural steel, shear span-depth ratio, degree of prestress, ratio of stirrup and thickness of web. The shear performance was evaluated based on cracking pattern, load–deflection behavior and shear ductility. Test results showed that prestressed ultra high strength concrete encased steel beams had higher residual shear capacity and post-cracking stiffness as well as by far better shear ductility than prestressed ultra high strength concrete beams. In addition, influence of experimental parameters on the shear performance of prestressed ultra high strength concrete encased steel beams and prestressed ultra high strength concrete beams also was discussed and compared, respectively.