Study On Mechanical Behavior And Design Method Of Steel-concrete Composite Pylon Anchorage System With Steel Anchor Box

In order to promote popularization and application of steel-concrete composite pylon anchorage system with steel anchor box in our country, this paper took built-in and built-out steel anchor box anchorage system as research objects to study the performance and design methods for anchorage systems, by building refinement finite element model and simplified framework. The main research contents of this paper were as follows:Taking the modes of connection and separation in steel anchor box into account, this thesis studied the effect of connections on mechanical characteristics and load transfer modes of multiple segments built-in and built-out steel anchor box anchorage system by finite element analysis. The results showed the steel anchor boxes were connected together could help to stress diffuse. The distribution homogeneous degree of members stress and studs shear force in connection system were better than those in separate system. The value of cable force distributed in the entire segment pylon anchorage system changed indistinctly by varying connection modes, while each member of the pylon anchorage system changed evidently.Transfer mechanism of built-in and built-out steel anchor box anchorage system was analyzed respectively by finite element analysis. Load path of the anchorage system was studied under bilateral cable force and unilateral cable replacement force separately. The force value of each member in the anchorage system distributed from cable force was analyzed quantificationally. The thesis clarified the load transfer path and load distribution relationship of single section cable force in multi section anchorage system.The mechanical performance was analyzed comparatively between built-in and built-out steel anchor box anchorage system by the finite element analysis. Similarities and differences of force features between the two forms of anchorage system such as the steel member stress distribution, the tower wall crack development process and the stud shear distribution characteristics were researched. This thesis also studied their difference in load transfer path and load distribution relationship.Finite element analysis was adopt to study the mechanical performance of stud shear connector in steel- concrete composite section of anchorage system. Formula to calculate the shear strength of stud shear connector was proposed on account of the worldwide 233 push-out experiment results. This thesis studied the group studs effect and its parameter sensitivity of group studs shear connector, the result showed that: ①The group studs effect would sharply reduce the average shear strength and shear stiffness of studs, bring the phenomenon of load-transferring nonuniformly, and also influence the axial stress of studs, but had no significant impact on the value of shear stress and normal stress and their distribution along the stud. ②With the increase of the number of studs layers, the average shear strength and shear stiffness of studs decreased, while the degree of load-transferring inhomogeneous degree of studs increased gradually. ③When the space between stud layers was increased from 2.3 to 13.6 times the diameter of the stud, the average shear strength of stud increased in the beginning and then decreased, and the average shear stiffness decreased gradually, while the load-transferring inhomogeneous degree of studs decreased at first and then increased. ④When the failure mode of group studs shear connection was bending-shear failure, the average shear strength had no obvious changed when the concrete strength grade increased, but the shear stiffness and load-transferring inhomogeneous degree of studs increased obviously. ⑤A reasonable layer spacing arrangement of studs was given in this paper according to the analysis results. The thesis gave a shear strength calculation method for group studs shear connector of steel anchor box at last.Combine with the mechanical characteristics of built-in and built-out steel anchor box anchorage system, and based on the principle of deformation coordination, the thesis established a simplified calculation method of load distribution in the anchorage system. The key construction design method of the anchorage system was studied. The thesis proposed a design method of steel anchor box anchorage system.