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Reliability levels obtained by Eurocode partial factor design - A discussion on current and future reliability levels

N.E. Meinen1, R.D.J.M. Steenbergen1, 2

1 TNO, Department of Structural Reliability, Delft, the Netherlands
2 Ghent University, Faculty of Engineering and Architecture, Department of Structural Engineering, Belgium

To assess the reliability of a structure, reliability based codes such as EN1990:2002 allow for the application of full-probabilistic methods and semi-probabilistic methods (i.e. the partial factor method). In principle, both methods should be equivalent and lead to (approximately) the same reliability level. In this study, this equivalence is assessed by investigating the structural reliability of a large number of structural elements designed according to EN1990:2002 partial factor method. Several material types, failure modes, variable loading types and load ratios are investigated. Both the one year reference period and the fifty year reference period are assessed and compared. For the future developments of EN1990, several suggestions are made to obtain a more uniform reliability level over different load-ratios between self-weight, permanent loads, and variable loads. Most important recommendations for EN1990 are: (i) to switch to the one year reference period for the reliability based design and assessment of structures and structural elements; (ii) to lower the partial factor for self-weight for material types with low variability; (iii) to include a slightly larger partial factor for wind and snow loads. It was demonstrated that neither of these suggestions would require any change or recalibration of the material dependent Eurocodes.

Key words: Structural reliability, partial factors, safety format, probabilistic framework, Eurocodes