Calibration of Wind Action Combination Factors from Experimental Data

The semi-probabilistic method is currently used worldwide for the assessment of structural reliability. In European Countries, both partial factors and combination factors recommended in EN1990 are adopted. However, in the case of climatic actions, this choice can lead to overestimation or underestimation of design values of the actions, and calibration at the National level would be appropriate. Based on wind climate data available in the literature, an attempt is made to calibrate combination factors for wind action combined with imposed loads for Italy. Two methods are considered: the classical simplified method based on the Ferry-Borges and Castanheta’s approach and Turkstra’s rule, and a method based on the numerical simulation of the combined load effects. First, the variability of combination factors over Italy is shown. Then, the influence of uncertainties and of the imposed load model is evaluated. Finally, the differences between the two methods are discussed and a comparison with current combination factors suggested by Eurocode 0 is made. Overall, it is shown that: local combination factors change over Italy without any correlation with the geographic coordinates; the simplified method overestimates combination factors; current values suggested by Eurocode 0 overestimate the combined load effects.