Research On Mechanical Behavior Of Concrete-filled Steel Tubular Planar Frame Under Long-term Loads

Considering the creep and shrinkage is the inherent nature of concrete under long-term loads, On the one hand, it can reduce the components and the integral structure stiffness, On the other hand it will produce great influences to deformation characteristics and bearing capacity of components and the integral structure. So it is necessary to research the mechanical properties about concrete filled steel tube joints and frames under long-term loads.The main achievements of this paper includes the mechanical properties of concrete filled steel tubular columns to steel beam planar frames. It can be summarized as follows:(1) For calculating load versus displacement curves of CFST axial compressive component under long-term loads, the general purpose FEM software ABAQUS was used to build mechanical properties analysis model of CFST axial compressive component under long-term loads. The calculated results by ABAQUS agree well with experimental results.(2) The general purpose FEM software ABAQUS was used to build mechanical properties analysis model of steel beam to concrete filled steel tubular column connections and planar frame. The main parameters that affected the strain-time relationship and stress field of steel beam to concrete filled steel tubular column connections and planar frame were analyzed, for example: the steel ratio of the column section, steel strength, long-term load ratio, stiffness ratio of beam to column, concrete strength and so on.(3) The general purpose FEM software ABAQUS was used to build one-story one-span concrete filled steel tubular columns to steel beam planar frames wether under long-term loads or not, the stress distribution of the core concrete, steel pipe, the steel beam flange and the web were all considered as analysis parameters.The main parameters of one-story one-span, two-story two-span and three-story three-span concrete filled steel tubular columns to steel beam planar frames were analyzed. Layer, cross number, the steel ratio of the column section, steel strength, long-term load ratio, stiffness ratio of beam to column, concrete strength , that affected the strain-time relationship were all considered as analisis parameters.Contrast analysis was made on the stress distribution, the strain-time relationship, the stress-time relationship of two-story two-span concrete filled steel tubular columns to steel beam planar frames with or without sidesway under long-term loads was analyed.