Optimal placement of skylights

Optimal placement of skylights


Skylights and diaphragm forces

When thin-plate materials of steel are used for diaphragm action, there is, according to DS446:2000, some geometrical requirements for skylights which must be complied with in order to account for the diaphragm action in the construction. According to EC 3, these rules can be eased since the requirements are stated as: “Openings to 15% of the relevant area are acceptable if justified by detailed calculations.”

In SkanDek’s experience there are no problems with diaphragm action according to the old rules in DS446, and if these are complied with it, is not necessary to further demonstrate the carrying capabilities of the diaphragm. However, if these rules are not complied with, a more detailed and complex calculation is necessary to demonstrate diaphragm action in the SkanDek panels.

Basic requirements for skylights, their placement and geometrical size according to DS446:2000:

  • Rim zone where skylights must not be placed corresponding to 25% of the disc’s smallest side measure. That is 0.25*22 m =25 m.
  • Maximum area of skylights corresponding to 15% of the disc’s area. That is, 0.15*60 m*22 m = 5.5 m.
  • In cross section parallel to the disc’s side measures, the total width of the skylights must not exceed 25%of the disc’s width in the specific direction. That is, a maximum total width of skylights corresponding to 0.25*22 m =5.5 m, and a maximum total length of skylights corresponding to 0.25*60 m = 15 m
  • 1,5b<L<4xB – should be complied with.

The building geometry in question is shown in the figure below, where the rim zone is marked with a dotted line. The skylights shown are 2.75 x 1.2, which is in compliance with the geometrical requirements.

In this case the building’s outer walls function as stabilizing walls.

Links and downloads

Click on the picture and get all skylights details as pdf