| There are more and more research on curved box girder with its widely used in modern engineering. Because the stress state of curved box girder is very complex, the classic thin-walled bar theory based on linear hypothesis can't meet the analysis requirement in reflecting the deformation characteristic, and the theory of box girder needs further improvement. This thesis established a nonlinear calculate theory and a curved beam element can simulate the stress state of curved box girder preferably based on thin-walled bar theory and finite element method to enrich and develop the theory and analysis method of thin-walled structural. This thesis has made the main characteristic contribution as follows:1. Combined with thin-walled bar theory and finite element method,a kind of geometry nonlinear thin-walled box girder element which can considering bending, bending-torsion, compression-bending and shear lag effect based on the energy method was established.2. It constructed shear lag warp displacement function of thin-walled box girder, and gave the displacement parameter and space displacement field of box girder. It established a shear lag analysis theory of curved box girder, and provided a new method for the nonlinear research of thin-walled curved box girder's shear lag.3. Based on finite deformation theory,principle of minimum potential energy and variational method, and used the Updated Lagrangian(U.L) formulation to derive the geometry nonlinear control differential equation of curved beam.4. Element stiffness matrix of the variable curvature thin-walled curved beam is developed according to the incremental equation of nonlinear Lagrange, and code the corresponding computer program with Matlab.5. Nonlinear behavior of curved box girder was analyzed by used of the thin-walled curved beam element calculation theory, method and computer program in this paper, and compared with finite element method to verified its rationality.
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