Eurocode 1 Wind load on free-standing walls and parapets (net pressure coefficients)

Calculation of wind load action effects on free-standing walls and parapets. The net wind pressure for zones A, B, C, D along the length of the structure are calculated from the net pressure coefficients corresponding to the overall effect on the front and back faces
According to:
EN 1991-1-4:2005+A1:2010 Section 7.4.1
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.
All Calculations
The basic wind velocity is given as vb = vb,0cdircseason where the fundamental value of basic wind velocity vb,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 cdir = 1.0 and cseason = 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.
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.
Wind terrain category 0 Wind terrain category I Wind terrain category II Wind terrain category III Wind terrain category IV
Illustration of Terrain categories reproduced from EN1991-1-4 Annex A
For walls standing on the ground hbase = 0. For parapets on buildings hbase is the height of the building
Length of return corner, approximately perpendicular to the wall face, as shown in EN1991-1-4 Figure 7.19
Solidity ratio φ = 1.0 corresponds to solid walls. Solidity ratio φ = 0.8 corresponds to walls with 20% openings. Solidity ratios less than 0.8 are not supported in this calculation

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.