Z and C Purlin

Secondary members are load carrying members suitable to ensure the stability of the building against forces in any direction
They include purlins and girts, eave strut, cable bracing and open steel web joists.

Secondary members have two other functions

Act as struts that help in resisting part of the longitudinal loads that are applied on the building such as wind and earthquake loads
Provide lateral bracing to the compression flanges of the main frame members thereby increasing frame capacity.