| A multilevel superelement substructuring approach for linear-static analysis of rectangular boxlike caissons is developed. The structure is considered as an assemblage of superelements in three substructural levels. These are panel, layer, and caisson superelements. Each superelement substructure is derived by applying the principle of static condensation.; Rectangular 9-node flat shell elements, which are composed of membrane stress and Mindlin plate bending elements, are assembled together to make the stiffness and load matrices of each panel substructure. Every panel substructure is condensed to a panel superelement. Then all of them in a layer are assembled together and condensed to layer superelement. Finally, the later superelement(s) are assembled and condensed to yield to caisson superelement.; After the assembling process, equilibrium equations are solved for the caisson superelement. Then a multilevel recovery process, with an inverse sequence of assembling one, gives the internal degrees of freedom for caisson, layer, and panel superelements, respectively. Finding all displacements, one can finally compute internal forces for every individual flat shell element.; This special purpose superelement substructure method provides considerable efficiency in practical analysis and design of boxlike caissons. Based on this approach, a computer program is developed which takes the most advantage from the repetition of similar individual elements and panels. Several numerical examples are solved indicating good agreement with other analytical or numerical methods and proper convergency for design purposes. |
