Mechanical Mechanism And Bearing Capacity Calculation Method Of Steel Fiber Reinforced High-Strength Concrete Six-Pile Caps

Reinforced concrete six-pile caps have been widely used in bridges under dynamic loads,multi-storey and high-rise frame structures,and substructures of large-span and large-flow aqueducts due to high bearing capacity and good stability.At present,the mechanical properties of ordinary strength concrete or steel fiber reinforced concrete six-pile caps were carried out by domestic and foreign scholars,but the research on the mechanical properties of steel fiber reinforced high-strength concrete six-pile caps has not been carried out.In this paper,the mechanical mechanism of steel fiber reinforced high-strength concrete six-pile caps is studied,the influencing factors of bearing capacity are analyzed,and the calculation method of bearing capacity of steel fiber reinforced high-strength concrete six-pile caps is proposed hereby incorporated experimental study and finite element analysis.The main contents are as follows :(1)Through the mechanical performance test of 8 steel fiber reinforced high-strength concrete six-pile caps,the crack appearance,development and failure mode of caps specimens were observed.The load-deflection curve of the caps,the distribution of concrete strain along the section height and the strain of the steel bar were studied.Test results show that the steel fiber reinforced high-strength concrete six-pile caps has experienced the failure process from bending to punching,and eventually punching failure occurs.(2)The effects of caps thickness,steel fiber volume fraction,concrete strength and reinforcement mode on the punching shear capacity of the caps were analyzed.The results show that the bearing capacity of steel fiber reinforced high-strength concrete six-pile caps is significantly affected by the thickness and the steel fiber volume fraction,but the volume fraction of steel fiber should not exceed 1 %,with the increment of concrete strength,the bearing capacity is improved,The bearing capacity of the thin pile caps is improved less obviously by using bunched bar arrangement.(3)The finite element analysis model of steel fiber reinforced high-strength concrete six-pile caps was established by ABAQUS finite element analysis software.The appropriate stress-strain constitutive relationship was selected to simulate the stress process of the caps under loading.The characteristics of crack distribution and stress-strain of six-pile caps were obtained.The punching failure mechanism of steel fiber reinforced high-strength concrete six-pile caps was further clarified by comparing with the results of six-pile caps specimens.(4)The mechanical mechanism of steel fiber reinforced high-strength concrete six-pile caps is expounded,and bearing capacity calculation method of steel fiber reinforced high-strength concrete six-pile caps is put forward.The punching shear mechanism of steel fiber reinforced high-strength concrete six-pile caps conforms to space strut-and-tie model,and the specimens fail as result of diagonal splitting of strut.On this basis,a calculation method for punching shear bearing capacity of steel fiber reinforced high-strength concrete six-pile caps was proposed based on the space strut-and-tie model.