Abstract: In the cylindrical shell connection structure assembled with bolted flange, the axial load is borne by the shell for compression, but by the bolted flange assembly for tension. When the tensile load is greater than the critical value, the existence of zero contact pressure region between flanges leads to local separation and loss of connection stiffness. which means the axial stiffness is nonlinear. To reveal the influence of structural parameters on the nonlinear stiffness under the preload, the theoretical model of bolted flange connection structure is established by constructing the deformation coordination mechanism of flange and cylindrical shell, based on the elastic thin shell theory and Couchaux improved beam theory. Compared with the finite element model, the theoretical model can correctly predict the initial stiffness and the change of the nonlinear stiffness in the separation stage of the bolted flange connection. By using the theoretical model, the influence of design parameters such as bolt preload, assembly position and flange thickness on the separation condition, separation behavior and nonlinear stiffness in separation stage of bolted flange connection structure is further studied. The variation trend of the separation critical load with the design parameters is obtained.

Key words: nonlinear stiffness, bolted flange connection, column shell structure, structural separation, critical load