The effect of end diaphragms on the local and global buckling of a new cold-formed cellular deck

Composite floor construction incorporating steel decking has been used successfully for over half a century (Dallaire, 1971) and is now the preferred type of floor in steel-frame buildings in most developed countries. Unpropped spans are preferred to simplify and accelerate construction, but maximum spans have typically only been in the range from 2.5 to 3.6 metres in Australia for decks less than 80 mm deep. This has controlled the spacing of secondary steel beams, and to a large degree the economics of the composite steel-frame system. Its use in other types of building construction in Australia is growing rapidly, particularly in all types of concrete-frame buildings. While unpropped spans in the vicinity of 5 to 6 metres have been achieved by using trapezoidal decks about 200 mm deep, there are many disadvantages that preclude their use in general steel-frame or concrete-frame building construction. For example: they form one-way, ribbed slabs with very limited two-way action; and their minimum overall depth can exceed 300 mm to achieve necessary fire and acoustic ratings. Also, being roll-formed from a single flat steel sheet limits their structural efficiency due to a constant material thickness around their perimeter. Moreover, of particular relevance to this paper is that these deep decks may have to be fitted onto fully-closed, full depth end diaphragms pre-fastened on site onto steel beam supports, to resist spreading and web crippling of the trapezoidal profiles that occur at the ends where support reactions are concentrated and shear forces are at their maximum.