Mechanical behavior and bearing capacity calculation method of steel fiber reinforced high strength concrete three-pile caps

The experiments of 10 specimens of steel fiber reinforced high strength concrete (SFHSC) three-pile caps, which have the plane dimensions of 831 mm×831 mm×831 mm and the varied thickness from 200 mm to 400 mm, were conducted. The crack distribution, load-deflection curve, concrete strain and longitudinal reinforcement strain of pile caps were measured. The factors, such as the steel fiber volume ratio, effective thickness, reinforcement ratio and reinforcement layout, and the concrete strength, on the bearing capacity of the pile caps were analyzed. The results indicate that the failure mode of the SFHSC three-pile caps is the punching failure, and its transfer mechanism can be similar to strut-and-tie model. With the increase of the steel fiber volume ratio and the effective thickness, the bearing capacity of pile caps improves evidently. The reinforcement ratio and reinforcement layout also have some effects on the bearing capacity of pile caps. Based on the experimental research and theoretical analysis, the relative formula is put forward for calculating the bearing capacity of SFHSC three-pile caps in conjunction with that of HSC three-pile caps, which can serve as a reference for the 'Technical Specification for Fiber Reinforced Concrete Structure' in China. ©, 2015, China Water Power Press. All right reserved.