Design and behavior of light composite steel–concrete trusses with drilled standoff screw shear connections

Composite steel–concrete flexural members have become increasingly popular in the design and construction of floor systems, structural frames, and bridges. A subtype of such composite floors is a system featuring composite trusses, also referred to as composite open-web joists, which can span large lengths and provide open web space for the installation of typical utility conduits. One problem that arises with respect to composite joists has been the installation of welded shear studs. In many composite trusses, the composite action can significantly reduce the required size and thickness of the top chord. The thinner the top chord member becomes, the more difficult it is to weld studs without burning through the base member. Likewise, as the joists get smaller, the greater the sweep (lateral out-of-straightness) tends to become. For these reasons, a form of shear connector other than welded shear studs is of interest. The results of the elemental push-out tests, analytical study and the resulting strength prediction models for the strength of the shear connection have previously been presented by the authors. This paper presents the analytical and experimental findings pertaining to the design and behavior of composite truss members with standoff screws as shear connectors.