Abstract: Arch structure is discretized into space curved beam elements. The initial and deformed configuration are described by the cylindrical co-ordinate system. The Green strain tensor is formed. The displacement components of the curved element are interpolated using cubic polynomials. It is assumed the plane section of the curved beams remains Plane during deformation, but not necessarily perpendicular to the neutral axis The membrane locking and shear locking are eliminated by the Method of Weighted Residuals. Thin-walled multicell box girder is discretized into space beam elements. The displacement field of the beam elements is constructed, based on the assumption of plane section and Cartesian co-ordinate system. Bending, torsion, torsion warping, cross-section distortion distortional warping and shear lag effect of the box girder are taken into account in the present analysis. A computer Program has been written. Good agreement between the computed results and the experiment results is achieved. The ultimate load of an engineering case is obtained.