EN 1991-1-4 : Wind actions
Prof. Pierre SPEHL
Technical Control Bureau for Construction
www.seco.be
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Contents of EN 1991-1-4
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1.1 Scope
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Storm of 25 Januari 1990
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4. Basic wind velocity vb
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Fundamental value vb,0 of the basic wind velocity
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Wind velocity measured in BEAUVECHAIN
airport (Belgium) on 25 Januari 1990 (knots)
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Wind velocity measured in BRUSSELS
(Belgium) on 25 Januari 1990 (knots)
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Annex A : Terrain roughness (categories 0, I et II)
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Annex A : Terrain roughness (categories III & IV)
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4.3. Mean wind velocity vm(z)
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Table 4.1 : Terrain parameters
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Figure 4.1 : Assessment of terrain roughness
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Transition between roughness categories
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Upstream distance x (m)
(National Annex of Belgium, France & Luxembourg)
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Orography factor co
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Wind deviation around a building
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Neighbouring structures
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4.5. Peak velocity pressure qp(z)
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Exposure factor ce(z)
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5.2. Wind pressure on surfaces
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Reference height for external pressure ze
(Figure 7.4)
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Reference height for external pressure ze
(Figure 7.4)
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Zones for vertical walls (figure 7.5)
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External pressure coefficient cpe for vertical walls
(figure 7.2 & Table 7.1)
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Conical vortices (flat roof)
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Zones on a monopitch roof (figure 7.7)
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External pressure coefficient cpe for monopitch roofs
(Table 7.3a)
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Conical vortices (duopitch roof)
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Wind tunnel testing (Central station Antwerp)
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5.3. Wind forces
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7.6. Force coefficient cf
(figure 7.23 & 7.24)
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Plane lattice structure with angle members
(figure 7.33)
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End effect factor yl (Figure 7.36)
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6. Structural factor cscd
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Annex D : Structural factor
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6. Structural factor cscd
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Background factor B²
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Resonance factor R²
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Aerodynamic admittance function
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Power spectral density function SL
(figure B.1)
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Peak factor kp
(figure B.2)
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Vortex shedding (Annex E)
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Critical wind velocity vcrit,i
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Viaduc de MILLAU
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Thank’s for your attention
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