vindtryk

Vindtryk, or wind pressure, is the force per unit area exerted by moving air on a surface. It is a central consideration in structural design for buildings, bridges, and other structures, and is measured in pascals (N/m2). It arises from the dynamic pressure of air interacting with surface orientation and geometry.

Physically, wind pressure is described by q = 1/2 ρ v², where v is wind speed and ρ is air density (about 1.225 kg/m³ at sea level). The actual surface pressure p is the product of q and a pressure coefficient Cp, which depends on geometry, roughness, and flow conditions. Cp can be positive (outward push) or negative (suction).

On a building, windward surfaces experience positive pressure, while leeward surfaces and roofs often experience negative pressure due to suction and vortex effects. Edge effects and transient gusts can cause fluctuations in pressure.

Estimation of vindtryk relies on wind measurements, exposure, height, and terrain. International and national standards specify how to convert wind data into design loads. In Europe, EN 1991-1-4 (Eurocode 1) gives methods and exposure categories; in the United States, ASCE 7 is widely used. Design codes may also account for dynamic effects such as gust factors and vortex shedding, particularly for tall or slender structures.

Design applications include sizing cladding, façades, and structural frames to resist both average and peak wind pressures, ensuring safety and serviceability.