| Two efficient thin-walled box beam finite elements which can model extension, flexure, torsion, torsional warping, distortion, distortional warping and shear lag effects are developed using an extended version of Vlasov's thin-walled beam theory. The elements can be used for the analysis of multicell box girder bridges with general geometry.; For straight right multicell box girder structures, an orthogonalization procedure is employed to uncouple the various distortional and shear lag modes. The governing differential equation pertaining to each action is used to derive the exact shape functions and the stiffness matrix and nodal load vector of the element. This exact shape function finite element model eliminates the need for dividing the bridge into many elements in each span. For curved box beam finite element, geometry mapping functions and the conventional polynomial shape functions are used to model bridges of general geometry, such as haunched and skew bridges. The application of the two elements is subsequently extended to the analysis of box girder assemblages. Considering thin-walled beam theory, the effects of prestressing, temperature, creep and shrinkage are also included in the analysis.; Finally, the two elements are used to perform linear elastic analysis of an extensive range of box girder bridges, the results of which are compared with other alternative numerical methods, such as shell finite element and finite strip method, and published experimental or prototype measurements. In practically all cases the results agree closely with other advanced methods of analysis. The advantages of the proposed method are its efficiency, ease of application, and the transparent way in which it deals with the different structural actions.; Two computer programs, SBOXEF and CBOX, which contain the proposed elements and method of analysis, are written in FORTRAN 77 and they run on either Apollo or SUN workstations. |
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