Study On Shear Behavior Of Prestressed High Strength Concrete Piles

Compared with other types of piles,prestressed high-strength concrete piles(PHC piles)have the advantages of relatively low unit price,large vertical load capacity,and large design range of pile foundation applications,therefore widely used in pile foundation Engineering,support engineering,bridge engineering and port engineering.In our country,there is no damage of pile foundation data,Japan as more occurrence and pile the applications of the more mature countries,from the existing pile foundation can be seen in the earthquake damage information,PHC pile under the action of earthquake prone to brittle failure,and the shear bearing capacity is low,is also no specification suitable for circular cross section of prestressed concrete members are given a calculation formula of ultimate shear capacity.In the PHC pile with only prestressed reinforcement,a certain amount of ordinary reinforcement can be added and arranged with the prestressed reinforcement to form the prestressed high-strength concrete pile(PRC pile).In this paper,the shear properties of PHC pipe pile and PRC pile with the same parameters were tested under different shear span ratios,and the effects of different shear span ratios and the addition of ordinary reinforcement on the shear properties of PHC pile were studied through experiments.Due to the limited specimens,on the premise of verifying the reasonable finite element model,the influence of shear span ratio,longitudinal bar ratio,concrete strength,axial compression ratio and other factors on the shear properties of pile was analyzed through finite element simulation.And stress distribution of the whole process of typical component is analyzed,the load deflection curve through the deformation of specimen at different stages of development for the definition of feature points and feature phase combination test pile test value and the shear strength of a large number of finite element simulation of the pile bearing capacity under different parameters calculated value were analyzed,and the paragraphs from the stirrup prestressed concrete items and the axial force contribution than against shear bearing capacity is verified and analyzed,put forward the consideration of the above parameters are revised formula to calculate the shearing resistance.The results show that the failure form of PHC pile is basically the same under small shear span ratio and large shear span ratio.From the point of the development of the number of distribution and crack width,crack development of PHC piles compared to PRC pile more fully,not only could improve the ultimate bearing capacity,and improve the ductility of pile components,component poor ductility prone to further ease the prestressed pile brittle failure problem,do ordinary reinforced for the ultimate bearing capacity and ductility of the pile has significant effect.The whole process of stress of prestressed concrete pile specimens with shear property was analyzed.Four characteristic points,point A,point B,point C and point D,were defined on the load-displacement curve of A typical specimen model.The load-displacement curve was divided into three stages :(1)elastic stage(AB);(2)elastic-plastic stage(BC);(3)stable section(CD)using finite element analysis software for parameter analysis,it can be seen that with the increase of shear span ratio,the elastic section of the load-displacement curve gradually decreases,while the plastic section increases,and the ultimate bearing capacity of members also gradually decreases.The shear bearing capacity of the pile can be improved by increasing the strength of concrete and the ratio of prestress reinforcement.The ultimate shear bearing capacity of the members increases with the increase of the axial pressure ratio.The modified formula for calculating the bearing capacity is presented by the finite element simulation results.