Secondary Structural Framing

Purlins, girts and eave struts are secondary structural members used to support the wall and roof panels.  Purlins are used on the roof; girts are used on the walls and eave struts are used at the intersection of the sidewall and the roof. Secondary members have two other functions: they act as struts that help in resisting part of the longitudinal loads that are applied on the building such as wind and earthquake loads, and they provide lateral bracing to the compression flanges of the main frame members thereby increasing frame capacity.

Secondary Structure The secondary structural members (purlins, girts and eave struts) are designed in accordance with the 1986 Edition of the American Iron and Steel Institute (AISI). Cold-Formed "Z" Sections Cold-Formed "C" Sections Eave Strut Section Secondary Framing Details Purlins, girts and eave struts are available in two standard surface finishes and in six standard thickness as shown in the table below:

Standard Material Surface finish Specifications (equivalent to) Available Thickness (mm) Purlins/Girts Eave Struts Z-Sections C-Sections  Red Oxide (Primer) ASTM A607 Grade 50 1.5, 1.75, 2.0, 2.25, 2.5, 3.0 2.0, 2.5, 3.0 2.0, 2.5 Pre-Galvanized ASTM A653 Grade SS50, Class I 1.5, 1.75, 2.0, 2.25, 2.5 2.0, 2.5 2.0, 2.5