Reliability Assessment of Frame Structures Based on Ultimate Strength Analysis

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1. A system is developed for reliability assessment of spatial frame structures based on ultimate strength analysis. (1) Ultimate collapse is evaluated by using a linearized failure condition of the section under the combined effect of axial force, shearing forces, biaxial bending moment and torsional moment. (2) A plastic node method combined with a finite element method is used to generate the safety margins of ultimate collapse modes. (3) Stochastically dominant collapse modes are selected by applying the so-called branch-and-bound methods combined with heuristic operations.2. The system is successfully applied to ship main structures, which are modelled as spatial frame structures and subjected to various notional loading conditions. Probabilistic properties of ultimate strength of ship main structures are investigated through the numerical examples for a large tanker (240,OOODWT) and comparison with previous results for plane frame models. (See reference 1.)3. The system is also applied to typical plate structures having orthogonal stiffeners as a basic study on ultimate strength analysis of ship bottom platings, which are modelled as plane frames and subjected to combined in-plane compression and lateral pressure. Through numerical examples and comparison with previous researches, the applicability of the proposed methods is demonstrated. (See references 2 and 3.)