Study On The Mechanical Properties Of Concrete Filled Steel Tubular Lattice Column

Concrete filled steel-tubular structure's mechanical properties and design methods were studied by many scholars with its widely used in engineering. Compared with the large number of applications, CFST is not much research. In order to realistically simulate the concrete filled steel-tubular lattice column's mechanical behavior in the earthquake, the CFST column's mechanical properties under cyclic loading were deeply studied in this paper. The result of study can coordinate the relationship of the bearing capacity, stiffness and ductility, and can have great practical significance for engineering design.Basing on considering material nonlinearity, geometric nonlinearity and status-changing nonlinearity of the structure, numerically simulate mechanical behavior of concrete filled steel built-up stud by ANSYS. Then analyze the influences of concrete filled steel built-up stud caused by variation of steel ratio, axial load ratio, height of column limbs, strength of concrete and strength of steel. Finally, overall study bearing capacity, stiffness degradation, strength degradation, dissipation characteristics of concrete filled steel built-up stud and stress distribution of column limbs steel pipe, concrete, lacing members. Above all, the concrete research achievements are as follows: The main influencing factors of mechanical behavior of column are steel ratio and the height of column limbs. The steel ratio can be properly increased, but increased range should not be too wide. The reason is if steel ratio is too high, stress concentration of the bottom of column limbs steel pipe will be pricked and increased ranges of bearing capacity and stiffness of components will be decreased. The height of column limbs should be controlled strictly, because if the height of column limbs is higher, the bearing capacity and stiffness of column limbs will be lower. If the column limbs are too high, the components will be unstable and destroyed early, or even capacity of stuff can not be fully played. The influence of mechanical behavior of column caused by axial load ratio is little, so it only needs to satisfy the requirements of related specifications. The strength of concrete should not be too high, because it has little effect to the bearing capacity of column, and increasing the strength of concrete will cause economic performance decreasing and inconvenience of construction. So, suggest to use concrete which grade is C50 and C60 in the real construction. The strength of steel should not be too high, because although increasing the strength of steel can have wide increasing range of bearing capacity and stiffness, stress concentration of steel will be pricked. So, controlling the strength of steel reasonably are very important to the safety of structure and project cost. Therefore, suggest to use steel which grade is Q345 and Q390 in the real construction. Therefore, the actual project auto use a appropriate thickness, a reasonable slenderness ratio, a appropriate strength of steel and concrete, and a reasonable axial compression ratio in order to meet project needs.The mechanical properties of CFST lattice column under cyclic loading is deeply analysed. The results should provide the valuable data and reference for theory and design methods of CFST lattice column, and also explore of the new structure. This paper lays a good foundation for the further study of the CFST lattice column's mechanical properties.