Calculation of wind peak velocity pressure

Eurocode 1 Wind peak velocity pressure

Description:

Calculation of peak velocity pressure qp depending on the basic wind velocity and the terrain category at the location of the structure. The wind action on the structure (forces and pressures) can be derived from the peak velocity pressure.

According to:

EN 1991-1-4:2005+A1:2010 Section 4

Supported National Annexes:

In addition to countries that adopt the CEN recommended values for NDPs, the following National Annexes are also supported automatically: Finland, Portugal. The National Annexes of Germamy, Norway, Spain, Sweden, Switzerland are NOT supported.

Basic wind velocity

v_b

m/s

The basic wind velocity is given as v_b = v_b,0⋅c_dir⋅c_season where the fundamental value of basic wind velocity v_b,0 is defined in EN1991-1-4 §4.2(1)P and its value is provided in the National Annex. Altitude correction may also be specified in the National Annex for EN1991-1-4 §4.2(2)P. The directional and season factors are generally c_dir = 1.0 and c_season = 1.0. For particular cases values smaller than 1.0 may be specified in the National Annex for EN1991-1-4 §4.2(2)P.

Terrain category

The terrain categories are illustrated in EN1991-1-4 Annex A. The transition zones between terrain categories are specified in EN1991-1-4 §A.2.

Reference height from ground of the examined part of the structure

z_e

The appropriate reference height depending on the type of the structure is given in EN1991-1-4 Section 7. For buildings it is generally equal to the height of the building above ground, measured to the top, which may be a ridge or a parapet.

Orography factor at reference height z_e

c₀(z_e)

Orography factor larger than 1.0 may be applicable over isolated hills and escarpments. See EN1991-1-4 §4.3.3 and §A.3 for more details.