The potential of local instability of cold formed floor joists is such that one should consider a cold steel formed floor as a one way spanning system. Commonly the load might not have been extreme, but it was concentrated over a small area at mid-span. In some cases, the depositing of the construction material occurred when the material was delivered by a lumber yard.
Collapses have occurred under a variety of loading, including depositing CMU, studs bunched together, or concrete being cast. Of course, construction loads should not exceed manufacturer’s specifications, but several incidents have occurred when a lower load of construction material was deposited, and collapse occurred because the floor was unbraced. In some construction operations such bracing and fastening does not immediately follow the installation of the cold formed joists, leaving them in a potentially unstable condition. Manufacturers’ instructions clearly define the allowable floor loads, but these refer to a system where the joists are properly attached to decking and braced. Almost all had a common cause: floor overload during construction. Although not very numerous, these accidents have led to serious injuries and even fatalities. This is not just a recent trend, as several accidents of this type have been recorded since 2005. The correspondent reports that in recent years there have been collapses during construction of cold formed steel floors.
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