Research On Shear And Flexural Behaviour Of Prestressed Concrete Pipe Pile With Hybrid Reinforcement

Prestressed concrete pipe piles,especially prestressed high strength concrete pipe piles(PHC pipe piles),which have the advantages of high vertical bearing capacity,convenient construction,economical and environmental friendly and good durability,have been widely used in building foundation engineering,highway engineering and slope engineering.However,the horizontal bearing capacity of prestressed concrete pipe pile is relatively low,restricting its application in the foundation pit supporting engineering.In order to improve the horizontal bearing capacity of the prestressed concrete pipe piles,a number of non-prestressed reinforcement can be introduced into PHC pipe piles,forming prestressed concrtete pipe piles with hybrid reinforcement(PRC pipe piles).By means of experimental research and numerical calculation of shear and bending behaviour,combined with relevant theory analysis,the shear and bending capacity of PRC pipe pile were investigated,with corresponding calculation formula proposed.The following four sections were covered in this dissertation.(1)A total of 7 prestressed concrete pipe piles with hybrid reinforcement(PRC pipe pile)and 3 prestressed concrete pipe piles(PHC pipe pile)were tested,hence the test data of the two kinds of pipe piles,including cracking shear force,ultimate shear force,load deflection curve and shear crack development,were obtained.The shear behaviour of both kinds of pipe piles were compared,and the influences of non-prestressed steel bars,axial compression and shear span ratio were analyzed.(2)Flexural tests on 6 prestressed concrete pipe piles with hybrid reinforcement(PRC pipe pile)and 3 prestressed concrete pipe piles(PHC pipe pile)were carried out in this study.The test data of the two kinds of pipe piles,including cracking bending moment,ultimate bending moment,load deflection curve and flexural crack development,were obtained.The flexural behaviour of both kinds of pipe piles were compared,and the effects of non-prestressed reinforcement was explored.(3)Numerical models were developed to simulate the shear behaviour of pipe pile specimens.The numerical results were in good agreement with the test results.According to the obtained test and numerical data,a modified formula for calculating the shear capacities of PRC pipe piles has been proposed based on the form of the existing formulae for shear capacity.The test results and the calculation results of the modified formulae were used to evaluate the design shear capacity predicted by formulae in codes at home and abroad.(4)The equivalent steel strip method was used to calculate the normal section bearing capacity of PRC pipe piles.The simplified formulae for calculating flexural capacity of prestressed concrete pipe piles were developed,which are simpler and easier to use than the existing design method.The calculation results of simplified formulae were compared with the experimental data and calculation results of the existing bending formulae for PRC pipe piles.