AD 432: Wind loads on building canopies
The purpose of this AD note is to direct designers’ attention to PD 6688-1-4 as a source of design loads on building canopies and useful data and guidance relating to other topics.
A regular question for the SCI Advisory team relates to wind loading on canopies attached to buildings. A canopy may typically be provided over the entrance to a building, but questions arise as there are no coefficients provided in BS EN 1991-1-4.
Designers should refer to PD 6688-1-4, section 3.5, which provides force coefficients for canopies attached to the lower half of a building. Canopies attached to the upper half of a building should be assessed using the rules for free standing canopies fully blocked at one edge (the back or the side, depending on the wind direction). The forward reference in PD 6688-1-4 section 3.5 is incorrect – it should direct designers to section 7.3 of the Eurocode for loads on canopies.
It should be noted that when using the data provided in the PD, the reference height is the height of the building, not the height of the canopy. This is because gusts on the upper parts of the building can be directed down the building face onto the canopy.
The overall force coefficients tabulated in the PD in the downward direction are considerably larger than those in the Eurocode, particularly for shallow angle canopies attached at a relatively low level – so it is particularly important that the PD is consulted.
More generally, PD 6688-1-4 is a valuable resource with helpful guidance on such topics as non-simultaneous loads on faces, assessment of dominant openings, re-entrant corners and inset faces.
Contact: Richard Henderson
Tel: 01344 636555