Abstract: - Cold formed steel purlins are the widely used structural elements in India. Practically ‘Z’ sections are provided, where the span of the roof purlins is sloped and the length of the span is maximum. The objective of this investigation is to study the behaviors of cold formed steel ‘Z’ and “C” purlin sections.To determine the maximum load carrying capacity of the specimens and then study the possible modes of failure of the members. The Effective Width Method (i) ignores inter-element (e.g., between the flange and the web) equilibrium and compatibility in determining the elastic buckling behavior, (ii) incorporation of competing buckling modes, such as distortional buckling can be awkward, (iii) cumbersome iterations are required to determine even basic member strength, and (iv) determining the effective section becomes increasingly more complicated as attempts to optimize the section are made, e.g., folded-in stiffeners add to the plates which comprise the section and all plates must be investigated as being potentially partially effective. The Effective Width Method is a useful design model, but it is intimately tied to classical plate stability, and i n general creates a design methodology that is different enough from conventional (hot rolled) steel design that it may impede use of the material by some engineers in some situations.