Steel Buildings in Europe

Part 3: Actions 3 - 22 8 WIND ACTIONS 8.1 General This Section provides guidance to determine the values of the wind action to be used for the design of a typical single-storey building according to EN 1991-1-4. The design procedure is summarized by a flowchart in Figure 8.6 and Figure 8.7. A worked example dealing with the determination of the wind action on a single-storey building is given in Appendix B. The rules apply to the whole structure or part of the structure, e.g. components, cladding units and their fixings. A simplified set of pressures or forces whose effects are equivalent to the extreme effects of the turbulent wind represent the wind action. Wind actions should be classified as variable fixed actions. The relevant wind actions shall be determined for each design situation identified. Where, in design, windows and doors are assumed to be shut under storm conditions, the effect of these being open should be treated as an accidental design situation. 8.2 Methodology The response of the structure to the effect of wind depends on the size, shape and dynamic properties of the structure. This response should be calculated from the peak velocity pressure q p and from the force and/or pressure coefficients. 8.2.1 Peak velocity pressure The peak velocity pressure q p ( z ) is the velocity pressure used in the calculations. It depends on the wind climate, the reference height, the terrain roughness and orography. It is equal to the mean velocity pressure plus a contribution from short-term pressure fluctuations. The peak velocity pressure can be calculated using the following procedure. 1. Fundamental value of the basic wind velocity v b,0 The fundamental value of the basic wind velocity is the characteristic 10 minutes mean wind velocity, irrespective of wind direction and time of year, at 10 m above ground level, in open country terrain. It corresponds to a mean return period of 50 years (annual probability of exceedence of 0,02). The National Annex specifies the fundamental value of the basic wind velocity.