2.0 Literature ReviewTo obtain a better understanding of the buckling produced when loading the lugs of cold-formed steel top cap sections, many studies have been reviewed and evaluated.2.1 Problems of Puckling Stability of Formed PurlinsCold formed steel purlins are known to exemplify certain unique properties, in a structural sense, due to their low thicknesses, the manufacturing process, the high slenderness of the members of their cross sections and their section nature open. Hancock et. al. (5) identifies the three basic buckling modes present in cold-formed steel members in compression: local, distortion, and global buckling, as shown in Figure 2.1 below. Local buckling is a mode of buckling that involves only the bending of plates in linear junctions between adjacent plates, which remain straight. The distortion buckling mode involves rotation of the stiffened lip elements of the section around the flange-web junction. Finally, the overall buckling consists of a translation of the cross sections of the bar without section distortion. The latter mode can be either flexion-torsion buckling or Euler buckling. (INSERT ILLUSTRATIONS OF HANCOCK BUCKING) JM Davies (6) describes in his book "Recent Research Advances in Cold-Formed Steel Structures", the difficulties faced by engineers calculating local buckling as a consequence of increasing complexity of shapes sections that become increasingly complicated and the increasing importance of distortion buckling. It indicates that distortion buckling is at least as likely as local buckling and warrants similar considerations in design, but is less well known and documented. Takahashi et al. (7) was the first to publish an article delving deeper into this mode of attention. Schuste and Acharya (24) effectively demonstrate in their article the overly conservative nature of design codes when considering top hats. Pastor and Roure (13) illustrate the effect of bending on an open section by citing the hat section as an example and proving the behavior of the element in pure bending. More recently, Honfi (25) attempted to create hat section optimizations using genetic algorithms. It is clear that cold formed steel is an area that is growing in terms of growth and understanding, even though the purlins used are often considered obsolete. conservative in nature, even among those studied extensively, such as the C and Z cross sections. Top Hat cross sections have proven their value at shorter spans, but the literature actually shows it as a topic that requires further study depth to which I wish to contribute through this project..