IMPROVED C-SECTION STRUCTURAL MEMBER

摘要

An elongate structural member which is cold formed from rolled steel and which is in the form of a purlin. The structural member has a C-shaped cross section composed of two spaced-apart parallel flanges (10), a web (11) joining one end of the respective flanges, a lip (15) located at the other end of each of the flanges, a lip return (13) projecting into the C-shaped cross section from the marginal edge of each of the lips (15), and at least one longitudinally extending channel-shaped recess (16 or 17) formed within the web (11) and projecting into the C-shaped cross section. The structural member is characterised in that both of the lips (15) project outwardly from the C-shaped section to form an obtuse angle theta with the respective flanges. In forming both of the lips so as to establish the obtuse angle theta between the lips and the associated flanges, the flexural-torsional buckling stress of the structural member is enhanced without substantially increasing the potential for local and distortional buckling.