BENDING BEHAVIOR OF COLD-FORMED STEEL–CONCRETE COMPOSITE FLOORS

In cold-formed steel framing constructions, cold-formed steel-concrete composite floors built with concrete slabs and cold-formed steel joists are a common floor system.To investigate the bending behavior of such a floor system, two floor specimens with alternative slab materials were evaluated.The test results indicated that varying the slab materials had no significant influence on the ultimate bending capacity; however, the stiffness of the composite floor with a concrete slab was much higher than that of the floor with a gypsum-based self-leveling underlayment slab.A finite element model was developed and validated with the test results to simulate the bending behavior of the floors using the ANSYS finite element software.Parametric investigations were conducted through the verified finite element models.The results showed that the web depth-to-thickness ratio, span-to-depth ratio of the joist, and steel strength significantly affected the ultimate bending capacity of the composite floors, whereas the effects of screw spacing and concrete slab thickness were negligible.Finally, a simplified method was proposed to evaluate the ultimate moment capacity of cold-formed steelconcrete composite floors.The results obtained from the proposed method were validated by both experimental and numerical investigations of two full-scale cold-formed steel-concrete composite floors built with concrete slabs and coldformed steel joists.