How Are Façade Wind Loads Determined?

Façade wind loads are determined from the wind standard adopted in the country where the project is built, together with its national annexes where these exist. Basic wind speed, terrain roughness, topography, building height and geometry are the principal inputs. In façade design, the external pressure or suction on the surface must be assessed together with the internal pressure inside the building. Loads are also not constant across the façade: local effects can increase around corner zones, edges and geometric discontinuities. It is therefore important that the glass, profile and connection calculations use pressures appropriate to the position of the element concerned and to its effective load area. The overall wind effects determined for the primary structure are not the same as the local design pressures to be applied directly to façade elements.

For structures outside the geometric or methodological limits of the standards, for projects with significant interaction with surrounding buildings and for tall buildings of complex shape, boundary layer wind tunnel testing is a frequently used method. Pressure measurements allow local effects on the façade to be examined for different wind directions. The results are then organised into a loading plan arranged by façade zone and element load area, and used in the sizing work.