Study On Flexural And Shear Performance Of Prestressed Steel Strand Ultra-high Strength Concrete H-type Piles

With the development of construction industrialization in China,precast prestressed concrete piles are widely used in all kinds of projects with the advantages of reliable quality,high construction efficiency and low cost.The prestressed concrete pipe pile is the most widely used one because of its mature production technology and complete techniacal specifications.Prestressed concrete pipe piles combined with cement mixing piles are usually used in river bank protection and foundation pit retaining engineering,or the construction method of forming enclosure wall by placing recyclable steel in cement is adopted.The above methods have the disadvantages of low horizontal load-carrying capacity and poor deformation ductility of ordinary prestressed concrete pipe piles,pollution of construction mud and tedious recovery of section steel.In this paper,it is innovatively proposed to replace the traditional prestressed steel bars with bonded steel strands as the main reinforcement,develops the pre-tensioning prestressed steel strands ultra-high strength concrete H-type piles,and solves the problems of low horizontal load-carrying capacity and poor deformation ductility of ordinary prestressed concrete pipe piles.The flexural and shear performance of prestressed steel strands ultra-high strength concrete H-type piles are systematically studied in this paper.The main work can be summarized as follows:(1)The cracking moment and ultimate flexural load-carrying capacity of H-type piles are determined by the flexural performance experiments of the prestressed steel strand ultra-high strength concrete H-type piles,and the experiment results are compared with the calculated values of the code formula.At the same time,the experiment results of H-type piles are compared with the results of flexural performance experiments of prestressed concrete pipe piles with equal width and concrete strength,and the difference in deformation ductility,flexural load-carrying capacity and failure mode between them are studied.(2)The cracking shear force and ultimate shear load-carrying capacity of H-type piles are determined by the shear performance experiments of prestressed steel strand ultra-high strength concrete H-type piles,and the experiment results are compared with the calculated values of the code formula.The characteristics of H-type piles in shear load-carrying capacity,deformation ductility and failure mode are studied.(3)According to the experiment results of material properties of concrete specimens,steel strands and stirrups,the appropriate material constitutive models are selected,and the flexural performance experiments of H-type piles are numerically simulated by using finite element software.The difference of cracking moment,ultimate flexural load-carrying capacity and deformation ductility between the numerical simulation results and the experiment results is compared to verify the liability of numerical simulation,and the failure mode of flexural specimens is analyzed by numerical simulation.(4)According to the appropriate material constitutive models,the shear performance experiments of H-type piles are numerically simulated by using finite element software.The difference of cracking shear force,ultimate shear load-carrying capacity and deformation ductility between the numerical simulation results and the experiment results is compared to verify the reliability of numerical simulation,and the failure mode of shear specimens is analyzed by numerical simulation.The aforementioned work can be the important basis for the design and the engineering application of the new type H-type piles.