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. 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 discussed. Arguments are given why the application of the one year reference period is recommended. For future code making, several suggestions are made to obtain a more uniform reliability level for the various load ratios of permanent to variable load. Most important recommendation for EN1990 is to lower the partial factor for the self-weight for material types with a small coefficient of variation, and to include a slightly larger partial factor for wind and snow loads. The suggestions are demonstrated to require no change or recalibration of material oriented building code parts.
Key words: Structural reliability, partial factors, safety format, probabilistic framework, Eurocodes