A HIGHER-ORDER THEORY OF THIN-WALLED GIRDERS WITH APPLICATION TO SHIP STRUCTURES

A new flexural and torsion theory of thin-walled girders is presented by introducing the concept of effective stiffness and mass parameters as modal quantities. For this purpose a rather simple vibration analysis of simple supported girders is performed. Due to sinusoidal modes the problem is reduced to the girder cross-section plane. The stiffness and mass properties are determined from equivalence of girder deformation energy and inertia work, respectively and its beam idealization that results in the same natural frequencies. Therefore, this beam theory is more accurate than the classical one. For practical reasons the finite element formulation is applied, employing orthotropic strip elements that are necessary for the ship structures. The developed computer program is tested in case of a square tube and a channel girder. For illustration, analysis of a container ship midship section is performed.