Towards a standardized procedure for the safety assessment of stability design rules

EN 1990 — Annex D contains a procedure for the safety analysis of resistance functions, based on First-Order Reliability Methods; this procedure permits the determination of appropriate values (in a semi-probabilistic design concept) of partial safety factors γ M on the basis of physical or numerical test results. In establishing the partial safety factor γ M of a design procedure, scatter related to material and geometrical properties may be isolated from resistance model. In this paper, firstly, an analytical review of existing methodologies for the safety assessment of design rules for steel structures is carried out and followed by the application of different assumptions and simplifications. This analysis is focused on the safety assessment of stability failure modes. Main simplifications relate – firstly – to the isolation of scatter related to material and geometrical properties from the resistance model and – secondly – to the assumption that the basic variables are independent from each other. The assessment is performed using available statistical distributions of basic variables such as the yield strength and cross-section properties. A sensitivity analysis is then performed. This study is done on the basis of the example of flexural buckling of steel column, leading to a general numerical validation of the simplified procedures and the proposal for a standardized assessment procedure for the safety assessment of the partial safety factor γ M for stability problems.