A consistent approach to the calibration of partial factors for permanent and variable loads in the 2nd generation of the Eurocodes

Abstract

In view of the development of the 2nd generation of structural Eurocodes, a discussion about target reliability levels and the calibration of partial factors for actions has started and it is currently ongoing. In the paper, a consistent approach for the calibration of partial factors for permanent and variable loads is presented, duly considering the role of additional safeties which are generally introduced in the design when dealing with climatic actions. The presence of increased (biased) load values in wind and snow hazard maps is detected for several countries in Europe, and its role in the calibration of partial factors and evaluation of reliability levels is investigated and discussed. The results prove the importance of accounting for such safe-sided assumptions in the calibration process in a consistent approach for the definition of climatic hazard maps at the national level. Considering that values of climatic actions provided by the hazard maps are affected by such a bias, the target reliability levels recommended by the Eurocodes are met; on the opposite, disregarding the bias, an unjustified increase of recommended values of partial factors is apparently needed to achieve the target reliability, so inducing higher building material consumptions and, consequently, less sustainable constructions.