Dynamic Characteristics Of Steel-Concrete Composite Curved Box Beams

In recent years, the application of steel-concrete composite box beams has been gradually increasing in the fields of buildings and bridges. Composite curved box beams can not only take advantages of both steel and concrete, but also exhibit smooth and comfortable line, beautiful appearance and easy arrangement, thus they have been widely used in architectures, overpasses, railway bridges and so forth. However, due to the complexity of structure stress in steel-concrete composite curved box beams, little related research was conducted domestic and abroad, especially the theoretical analysis and experimental study on the dynamic characteristics. Therefore, it is urgently needed to explore the dynamic characteristics of steel-concrete composite curved box beams.The main research work completed in this thesis can be concluded as follows:(1) Based on the energy variation principle, the dynamic analysis models of steel-concrete composite curved box beams were established considering the interface slip, shear deformation and the shear lag effects. The out-of-plane vibration differential equations and the corresponding boundary conditions of steel-concrete composite curved box beams were derived, which can be degraded to the out-of-plane vibration differential equations considering both the surface slip and shear deformation effects. The corresponding calculation programs were written by MATLAB to calculate the free vibration frequencies of composite curved box beams under the three boundary conditions mentioned above.(2) Finite element models of the clamped, simply supported and two-span continuous composite curved box beams were established by ANSYS software to analyze their dynamic characteristics and each free vibration frequency was obtained. The results show a good agreement between the calculating results and the ANSYS simulation results, verifying the correctness and reliability of theoretical analysis results in this thesis. (3) According to the structural characteristics of steel-concrete composite curved box beams, a series of composite curved box beams with different slip stiffness, span-radius ratio and cross-sectional size ratios under different supporting conditions were studied. At the same time, the influences of interface slip and shear lag effect on the inherent vibration characteristics of steel-concrete composite curved box beams were discussed and some reasonable advice was given from the point of view of dynamics.