9. Defining a restrained purlin

Only members with cold-formed profiles can be defined as restrained purlins, where the presence of connected sheeting is taken into account and reinforces the member in buckling. The data required to dimension a member defined as a restrained purlin are given in a separate page as seen in the image below:


Sheeting data

The sheeting data can be found in the datasheets provided by the panel or sheeting manufacturer and depend on the shape of the sheeting and the method used to connect it to the purlin.

  • Ieff : Effective inertia of the sheeting per meter length. This data comes from the manufacturer’s datasheets and must be entered in the displayed units.
  • Sheeting support : Selection of the support type of the sheeting on the purlin. Can be Continuous or Simply supported.
  • Distance between purlins : Distance between purlins in current units of length.
  • Connecting bolts per meter : Number of bolts connecting the sheeting to the purlin per meter length.


For each opening covered by the purlin, the length of the opening and the number of anti-sag rods within the opening must be entered.

Loading cases

In the loading cases table, the user must enter the transverse load and its result as pressure or suction on the sheeting, for every loading case that will be used for dimensioning.