Peak velocity pressure to EN 1991-1-4 Eq. 4.8: basic wind velocity, terrain roughness, turbulence intensity and q_p at any height. Run the free template.
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About this Peak Velocity Pressure Calculator
This calculator works the peak velocity pressure q_p at a reference height to EN 1991-1-4 Section 4, using the recommended values with no National Annex. The basic wind velocity is adjusted for direction and season, the mean wind velocity follows from the terrain roughness and the orography, and the peak velocity pressure adds the short gusts through the turbulence intensity (Eq. 4.8). It is the starting point for every pressure and force coefficient in the code.
- Structural engineer gets q_p at the reference height of a building, roof or element before applying pressure or force coefficients.
- Facade engineer checks how the design pressure on glazing and cladding changes with height and terrain category.
- Student or graduate engineer follows the chain from basic wind velocity to peak velocity pressure, with each equation numbered as in the code.
Change the basic wind velocity, terrain category or height and every step updates. It is an engineering-grade calculation you can keep and reuse in a CalcTree workspace.
More info on Peak Velocity Pressure
Basic wind velocity and pressure
The fundamental value of the basic wind velocity is multiplied by the directional and season factors (Eq. 4.1). The basic velocity pressure follows from the air density and the basic wind velocity (Eq. 4.10), and is reported alongside q_p for comparison.
Terrain category and height
The terrain category, selected from categories I to IV of Table 4.1, sets the roughness length z_0 and the minimum height z_min. Below the minimum height the profile is taken at the minimum height (4.3.2(1)), and the page reports the height actually used.
Mean wind velocity
The terrain factor k_r scales the profile against terrain category II (Eq. 4.5). The roughness factor c_r follows from the logarithm of height over roughness length (Eq. 4.4), and the mean wind velocity is c_r times the orography factor c_o times the basic wind velocity (Eq. 4.3).
Turbulence and peak velocity pressure
The turbulence intensity I_v is the turbulence factor over c_o times the logarithm of height over roughness length (Eq. 4.7). The peak velocity pressure adds seven standard deviations of the turbulence to the mean velocity pressure (Eq. 4.8), giving q_p in kPa.
Common Calculation Errors to Avoid
- Using a height below the minimum height The logarithmic profile is not valid near the ground. Below z_min the code takes the profile at z_min, and using the actual height understates or distorts q_p.
- Picking the terrain category from the site, not the upwind fetch The category describes the terrain upwind for the direction considered. A site in a suburb with open country upwind can need a rougher or smoother category than its own surroundings suggest.
- Forgetting the National Annex The recommended values are a default. The National Annex for the country of use can change the basic wind velocity, the directional and season factors, the turbulence factor and the profile.
- Ignoring orography Hills, ridges and escarpments raise the mean wind velocity. Where orography is significant, enter c_o from Annex A rather than leaving it at the flat terrain value.
- Confusing q_b with q_p The basic velocity pressure has no terrain, height or gust effect. Applying pressure coefficients to q_b instead of q_p underestimates the load.
Engineering templates
Common calculators
Design guides
FAQs
What is the difference between basic and peak velocity pressure?
The basic velocity pressure comes from the basic wind velocity alone. The peak velocity pressure includes the effect of terrain roughness, height and short gusts through the turbulence intensity, and it is the pressure the code's pressure and force coefficients are applied to.
Which terrain categories does the page offer?
Categories I to IV of Table 4.1, from lakes and flat open country to urban areas. Terrain category 0, sea or coastal areas, is not offered on this page.
What height range does the profile cover?
The terrain profile in Section 4 applies up to 200 m. Below the minimum height for the terrain category the minimum height is used.
How do I account for a hill or escarpment?
Work out the orography factor c_o from Annex A of EN 1991-1-4 and enter it. It scales the mean wind velocity and also reduces the turbulence intensity.
Can I use National Annex values?
Yes. The basic wind velocity, the directional, season and turbulence factors and the air density are all inputs, so values from the National Annex for the country of use can be entered in place of the recommended values.
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