2. Estimation of the Design Wind Speed

The modern approach to the specification of the design wind speed favours the explicit format which directly presents the design value of the wind speed instead of hiding the value behind the product of the characteristic wind speed and a partial factor. This approach leads to better reliability consistency in case of highly variable geographic conditions and it avoids underestimations for systems with unfavourable non-linear characteristics. Some leading codes therefore have adopted this concept. This chapter presents tentative target values of the exceedance probability of the design wind speed for the ultimate limit state with reference to the design working life considering six importance classes for buildings and structures. Additionally, tentative target values are given for the serviceability limit state with reference to a single year. For the practical application, strategies are discussed in regard to the quality check of data, the sampling of the appropriate ensembles and the estimation of the design value considering an appropriate confidence interval. Since statistical uncertainties remain large even for several decades of observations, a new approach is presented which leads to consistent values of the design wind speed. Additionally, the complex topic of directionality is addressed on the example of storms induced by strong frontal depressions.