Abstract: The mechanical response of a complex thin-walled rectangular structure subjected internal pressure load is investigated numerically based on finite element analysis (FEA) code MSC. Marc / Patran, and the nonlinearities of the material and geometry are both taken into account. The characteristics of deformation and the properties of stress distribution of this kind of structure are obtained, where the largest Mises equivalent stress are found to be located at the region between the reinforcement channels and the convex face in the molded units. And the critical buckling load of bottom molded-units of the reference model structure is found to be 80 kPa. The numerical model is validated experimentally with a real assembled thin-walled water tank. It is found that numerical predicated displacements as well as the stress of control points are in reasonable agreement with the experimental data. In the experiment, the failure modes of the structures are found to be buckling of bottom molded units, leaking at the corner of the molded units and fracture of stiffeners. Based on this numerical model, parameters such as the height as well as the diameter of the convex face, the position of the reinforcement channels and the arrangement of stiffeners, an optimum shape of molded unit is optimized, and the load-carrying capability of the structure is enhanced.

Key words: Buckling, Mechanical response Failure mode, Numerical simulation, Thin-walled structures