STRUCTURAL BEHAVIOR OF NEW THIN-WALLED COMPOSITE TRUSSED BEAMS AND PARTIALLY PREFABRICATED CONCRETE SLABS

Resumo

The composite trussed beams consist of a very traditional solution for building floors and
are associated to several benefits, such as reduced consumption of materials, excellent structural
response in terms of bending capacity, as well as flexural stiffness, ease of fabrication and erection.
Furthermore, the adoption of open-web composite beam enables larger free-spanning, compared to
traditional T-sections (composed by the association of hot-rolled I-shaped steel member and concrete

slabs), and allows the detailing of electric, hydraulic and HVAC (Heat, Ventilation and Air-
Conditioning) lines through the web of the trusses. One of the first researches regarding the structural

behavior of this type of composite floor system was conducted in 1960’s, from the experimental full-
scale tests in the United States. In the last 40 years, a lot of work has been published to provide

reliable information in terms of shear connection solutions, degree of interaction between the steel
trusses and concrete slabs, mechanisms of collapse and analytical models for the prediction of the
bending capacity. In almost all cases, the steel members are composed with hot-rolled sections (double
angle, for example) and the shear connectors are welded to the top chord of the truss. In this context,
the objective of the present work consists of presenting (a) alternative types of shear connectors, (b)
innovative structural floor system, composed by thin-walled trusses and prefabricated concrete slabs.

Three types of steel shear connectors were developed, manufactured with 0.95 mm thick plates: Thin-
Walled Perfobond, Thin-Walled Channel and Thin-Walled Vertical Post. The connection between the

connectors and the top chord of the trusses were provided with the help of 4.8 mm self-drilling screws.
Cold-formed lipped channel members (0.95 or 1.25 mm thick), partial prefabricated one-way concrete
slabs and styrofoam blocks compose the floor systems. Based on the results of an extensive
experimental program, important preliminary conclusions can be assessed. The obtained data revealed
higher bending capacity compared to traditional analytical predictions and excellent structural
response in terms of flexural stiffness and ductility.