Overview of the model factor for shell-type FE-models of steel I-section girders

Advanced design approaches based on finite element analysis (e.g. direct resistance check) are increasingly being applied in steel structural design practice. In the context of direct resistance check, where the resistance is derived directly from numerical analysis, further development is required to adequately address model uncertainties and to ensure compliance with the prescribed safety requirements of the Eurocode. Design procedures based on the finite element method must account for both the resistance model uncertainties traditionally considered in analytical design approaches (by having empirical design background) and those associated with numerical modelling, to achieve a level of safety consistent with the provisions of the Eurocode standards. This study summarises the methodology for assessing uncertainties on the resistance side and proposes model factors (γ FE ) for different failure modes (bending, shear and patch loading) adjusted to the failure probability criteria of EN 1990. The study focuses on models using shell elements and applies the results of previous laboratory experiments to determine the modelling uncertainties and the model factor for different failure modes separately. The methods used to define imperfections is also examined (application of equivalent geometric imperfections or initial geometric imperfections and residual stresses) from the model factor point of view and their application specialties are also highlighted.