| With the rapid development of the economy in the past forty years,the construction level of cable-stayed bridges in China has been at the forefront of the world.The pylon anchorage zone is an important component of the cable-stayed bridge structure.The cable tension is transmitted to the anchorage zone through the tower column,which affects the safety of the overall structure of the cable-stayed bridge.However,the research in the mechanical behavior and parameter analysis of the pylon anchorage zone is insufficient.The current bridge design specifications also lack specific instructions,resulting in that spatial FEM analysis and model test are often required to verify its effectiveness.And the research results cannot be directly applied to other construction projects.Based on the concrete damage plastic(CDP)model,the FEM analysis of the mechanical behavior of one-way PC pylon anchorage zone was investigated on the background of Xijiang Bridge,and the parameter effective design approach of the concrete pylon anchorage zone was also discussed.The main contents of this thesis are listed as the follows:(1)Using the basic theory of damage model,the characteristics of ABAQUS software's CDP model are studied,and the parameter input method of CDP model is given,which can be used to the nonlinear feature of concrete material.Through the uniaxial tension example,the constitutive relation of the concrete structure is consistent with the numerical simulation and the analytical solution under the two modes of linear softening and bilinear softening.It is reliable to verify that the ABAQUS software's CDP model can be used for nonlinear analysis of concrete structure.(2)The linear FEM analysis of the one-way PC pylon anchorage zone is carried out with the stress-strain state under three conditions: unidirectional prestress,normal working status and 1.6 times overload status.And compare the test results with the numerical calculation results.The research shows that both trends are basically the same,and data are well-matched.the one-way PC pylon anchorage zone is still in the linear elastic working state under 1.6 times of the design cable force,and the structural safety reserve is sufficient.(3)Combining the CDP model,the elastoplastic FEM analysis of the one-way PC pylon anchorage zone is carried out.The force transmission mechanism of the pylon anchorage zone is discussed,and the ultimate bearing capacity is obtained.The proportional ultimate load of the pylon anchorage zone is 1.605 times of the design cable force,and the ultimate state bearing capacity is 2.872 times of the design cable force.During the loading process of the one-way PC pylon anchorage zone,the chamfered part is first cracked,then the upper surface of the front wall is cracked and spreads to the periphery.When the structure enters the yielding stage,damage is found everywhere on the inner and outer surfaces of the entire front wall,some fixture of the outer surfaces of the front wall near the cable guide is close to the yielding state,and the concrete of the entirely front wall is destroyed.When the structure is destroyed,the side wall only has local damage at the chamfered position,and the other areas have no obvious damage.There is still a compressive stress of about-2.1 MPa,and the one-way prestressed strands are still in the elastic range.(4)In view of the limitations of the existing performance of the pylon anchorage zone,the research work on the reasonable arrangement of the one-way prestressed strands,the analysis of the front wall thickness parameters and the analysis of the internal baffle structure are carried out.By numerical model analysis and comparison of the effectiveness of the three improved methods,a reasonable structural improvement and parameter analysis method are provided for the pylon anchorage zone with one-way prestressed strands. |
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