Approximate approach to progressive collapse analysis of the monotonous thin-walled structures in vertical bending

• Ultimate load capacity of the hull girder in vertical bending is considered.
• Progressive collapse analysis method based on Smith's approach is proposed.
• Validation is based on the numerical simulations using FEMAP/NASTRAN software.
• Obtained results are in a good agreement with results of the numerical simulations.

Present article proposes improved assessment of the ultimate bending capacity (ultimate bending moment), i.e. enhancement of the ultimate limit state evaluation in the concept design of the monotonous thin-walled structures predominantly subjected to vertical bending loads during their exploitation. An alternative progressive collapse analysis method is proposed, which incorporates direct consideration of various relevant distributed load effects and consequently enables more sophisticated evaluation of the ultimate bending capacity and more accurate and reliable identification of the critical cross section and its collapse sequence. Relevant aspects of the employed approximate model for the cross sectional warping due to vertical bending are considered and determination of the (longitudinal) warping displacements and strains, shear strains and stresses, as well as the corrected longitudinal strains is described. Influence of the (ultimate) shear capacity on the (ultimate) bending capacity is discussed and detailed description and critical overview of the proposed method is given. Finally, various aspects of the considered problem and accuracy of the proposed approach are discussed and demonstrated on example of the thin-walled box-girder, whereby detailed comparison of the results obtained by the proposed approach and nonlinear finite element method analyses is given.