Flexural Stiffness Of Concrete Filled Steel Tubular Truss Structure Research

With the rapid development of bridge construction in our country, concrete-filled steel tubular (CFST) structures are widely applied. However, a unified method for calculating the bending rigidity of CFST structure, a hot problem puzzled engineers, has not been put forward. Therefore, the dissertation carries out further research about the bending rigidity of ribs and trusses of CFST structure.At present, the popular methods of it are conversion section method, the methods employed by CECS28.90, DL/T5080-1999 and JCJOl-89, use of steel-concrete mode and etc. Based on analysis of various methods, the dissertation comprehensively considered the factors which influence the bending rigidity: the distance between the web-chord, the horizontal and vertical distances between the up-chord and low-chord, the radius of the up-chord, low-chord, web-chord and the link truss. Through numerous simulating calculations by SAP2000 and the fit method, the relationships between the above factors and the deflection are found. Then, the CFST structure is simplified to plane truss, whose function is deduced by substructure method. Matlab software is applied to make out the initial forces of the plane truss. Converted the plane truss to girder and substitute the initial force of the truss to that of the girder under the same condition, the equalized bending rigidity method of the CFST truss girder is reached.Compared the results of the above methods by specific projects, the initial forces differ slightly. But, the deflection calculated by equalized bending rigidity method is more approximate to that of the projects.