Wind action on free-standing walls at the Eurocode 1


by Thibaut FRETTÉ
Product Technical Specialist

Abstract

In this article, we will apply the procedure from the EN1991-1-4 to estimate the wind forces on a free-standing wall with a return corner.  

Keywords: Advance Design, wall, free-standing wall, Eurocode 1, EN1991-1-4, return corner

1. Introduction

Free-standing walls are covered in §7.4.1 from EN1991-1-4.

This part is intended towards fences as well as buildings with so many openings that they should be designed as per §7.3 (canopy roofs) and §7.4 (free-standing walls).

2. Theory

The Eurocode 1 defines two types of free-standing walls:

  • Without return corner
  • With return corner
Free-standing walls will be divided in A, B, C and D zones, depending on how long they are.

Pressure coefficients for each zone are determined from Table 7.9 and may require up to 3 successive linear interpolations based on:

  • The dimensions of the wall (Length/Height ratio)
  • The length of the return corner (if any)
  • The solidity ratio of the wall (also called opening ratio or porosity)

3. Example – Free-standing wall with return corner

Assume a free-standing wall (Length: 16m and Height: 4) with a 0,9 solidity ratio.

This wall has a 2m-long return corner.

3.1.            1st linear interpolation
We perform a 1st linear interpolation based on the length/height ratio of the wall (ignoring the return corner).

Yet, the values we have just obtained (in red) only stand for a wall without a return corner.

A 2nd linear interpolation is then required.

3.2            2nd linear interpolation

We perform a 2nd linear interpolation based on the length of the return corner (noted L’).

Yet, the values we have just obtained (in blue) only stand for a solid wall (φ = 1).
A 3rd and final linear interpolation is then required.

3.3.            3rd linear interpolation

We perform a 3rd linear interpolation based the solidity ratio of the wall.

The values we have just obtained (in green) are the ones we should expect for the A, B and C zones (the wall is not long enough to get a D zone).

There are the values the climatic generator from Advance Design 2023 will return:

Of course, Advance Design will consider all required wind directions (perpendicular and oblique winds).

Advance Design will also consider more complex effects, such the potential force reduction that can be benefited from an upwind wall, through the shelter factor (ψs) defined in §7.4.2:

4. Conclusion

The estimation of wind forces on free-standing walls sure is a tedious process, with a high risk of errors due to the various linear interpolations needed.

Fortunately, version 2023 of Advance Design now handles these structural elements, generating the corresponding forces on your 3D structures in a single click.

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