Dynamics Of Steel-Concrete Composite Box Beams

Abstract:Steel-concrete composite box beams have been widely used in high rise buildings and long-span bridge structures. Lots of research results on static performance of steel-concrete composite beams have been tested at home and aboard. However, research on the dynamic performance of steel-concrete composite box girder was seldom tested and relevant design provisions lags behind the engineering practice seriously. Study on dynamic properties of composite box beam is urgently needed, the research results can promote application of composite box girders in high-rise buildings and large-span bridge engineering.The main research works completed in this paper are as follows:(1) Based on energy variation principle, the dynamics analysis models of steel-concrete composite box beam were established considering the surface slip, shear deformation and the shear lag effects. The flexural vibration differential equations and the corresponding boundary conditions of Steel-concrete composite box beams were derived, and can be degraded to the vibration differential equations which only considering the surface slip and shear deformation effects. The Corresponding calculation programs were written by MATLAB software, calculating free vibration frequencies and modes of composite clamped beams, composite simply supported beams and composite continuous beams.(2) ANSYS finite element models of the clamped, simply supported and continuous composite box girders were established to analyze their dynamic characteristics, Each free vibration frequencies and the corresponding vibration modes were obtained. The correctness and reliability of theoretical analysis results in this paper were verified by comparing with ANSYS simulation results.(3) According to the structural characteristics of the steel-concrete composite box girder and the results of previous studies, the influences of interface slip and shear lag effects on the inherent vibialiun characteristics of the steel-conerete composite box girder were discussed.(4) A series of composite box beams with different slip stiffness, rations of width and thickness of floor, Cantilever ratio, rations of height and thickness of box beam web, rations of height and length of box beam, section height ratio were studied, analyzing the changes of dynamic characteristics of the composite box girders and getting the Reasonable design parameter values.