In the field of structural engineering, ensuring the safety and integrity of buildings and structures is of paramount importance. One crucial aspect of this process involves calculating the effects of wind forces on structures, as the wind can exert significant pressure and induce structural vibrations. Eurocode 1 (EN 1991-1-4) serves as a comprehensive standard for wind actions on structures within the European Union. This code provides engineers with guidelines and procedures for accurately assessing wind loads and their impact on various types of structures.

The theoretical background underlying the wind calculation methods prescribed in Eurocode 1 (EN 1991-1-4) is fundamental to understanding the rationale behind its provisions.

**Z0** - Roughness length, from Table 4.1

**Zmin **- the minimum height, from Table 4.1

**vm (z)** - Wind velocity at height

**l****v**** (z)** - Wind turbulence

**ce(z) **- Exposure factor

**qb** - Basic velocity pressure

**qp(z)** - Peak velocity pressure at a height

NOTE: For various national annexes the obtaining of qp(z) may vary.

**CsCd** - Structural factor equal to multiplication of the size factor CS and the dynamic factor Cd.

aerodynamic admittance functions Rh and Rb

**Cf** - The force coefficient

- For outdoor panels (signboards) separated from the ground by a height zg greater than h/4 (see Figure 7.21), the force coefficients are given by Expression (7.7):

**Cf** = 1.8 7.4.3 (7.7)

The geometry and position of the force are also described in Figure 7.21.

**NOTE:** *The user will get a warning at the automatic generation of the loads if the height conditions above are not fulfilled.*

- For canopies, the values of
**Cf**and the positions and geometries of the linea element in Table 7.6 and in Table 7.7 - For lattice structure or scaffolding:

**Where:**

A is the sum of the projected area of the members and gusset plates of the face projected normally to the face.

**Ac** is the area enclosed by the boundaries of the face projected normal to the face = d ∙ l (d is the width of the lattice and l is the length of the lattice).

**Where:**

**we** - Wind internal pressure

**Where:**

**ze** is the reference height for the external pressure given in Section 7

**cpe** is the external pressure coefficient. The coefficient, the position and the geometry of the external pressure are defined at Section 7, in:

- 7.2.1 General
- 7.2.2 Vertical walls of rectangular plan buildings
- 7.2.3 Flat roofs
- 7.2.4 Monopitch roofs
- 7.2.5 Duopitch roofs
- 7.2.6 Hipped roofs
- 7.2.7 Multispan roofs
- 7.2.8 Vaulted roofs and domes

**wi **– Wind external pressure

**Where:**

**zi** is the reference height for the internal pressure given in Section 7

**cpi **the internal pressure coefficient is defined in section 7 in 7.2.9 Internal pressure.

**w **- Wind bet pressure:

1. For an element of the type "Building", "Protruding roof" or "Vertical roof slope (shed)":

Knowing that for a specific structural part: ‘5.2 (3) The net pressure on a wall, roof or element is the difference between the pressures on the opposite surfaces taking due account of their signs’ and

For the standard EC1 and the EC1 French annex, the formula includes also the correlation coefficient Kdc for the windward or sheltered windward walls, resulting:

**For parapet walls, canopies, or awnings**

Where cp,net is the net pressure coefficient. The coefficient, the position, and the geometry of the net pressure are given in Section 7.

**NOTE****:** *For canopies the automatically generated loads are based on both the force coefficient cf and the net pressure coefficient cp,net. There are no mixed types of loads in the same load case.*

**Fw** - The resultant wind force used for outdoor panels (signboards), canopies or individual elements of lattices:

**Where:**

**cf** is the force coefficient for the structure or structural element, given in Section 7 or Section 8 (detailed above).

**Aref **is the reference area of the structure or structural element, given in Section 7 or Section 8.