Study On Bonding Behavior And Bending Behavior Of Steel Tubular Composite Pile

With the construction of large-scale deep-water foundation and port,the construction of cast-in-place pile requires long steel cylinder to keep the hole stable.After finished,it will form a composite pile composed of steel pipe,reinforced concrete and mud,called steel tubular composite pile.Steel tubular composite pile has the advantages of high strength,good plasticity,impact resistance and fatigue resistance,which depends on the synergistic effect of different materials in the process of force.At present,there are few researches on composite piles.By means of theoretical analysis,indoor test and field test,bonding behavior and bending behavior of steel tubular composite pile are studied.The main contents are as follows:(1)Bond-slip mechanism of steel tubular composite pipe is analyzed,and the constitutive model of steel tubular composite pile is deduced theoretically.According to the results of the push-out test,the ultimate bond strength formula and the bilinear bond-slip constitutive model are calculated through linear regression method.(2)According to the results of the push-out test and the pure bending test,bonding failure process and bending failure process of steel tubular composite pile are analyzed.The comparison test shows that mud will weaken the bonding behavior,but it has little influence on the bending behavior.The radius-thickness ratio shows negative correlation both on bonding behavior and bending behavior.(3)Based on the results of pure bending test and field horizontal bearing capacity test,steel tubular composite pile observes the flat section assumption,which can be used in the theoretical formula to simplify the derivation process.(4)The result of pure bending test shows that the general theory can be used to calculate the flexural capacity of steel tubular composite pile.Feld test shows that the bending stiffness of steel tubular composite pile will decrease gradually and finally keep stable,which can be calculated by the bending stiffness combination formula.