Structural response of hybrid timber ‐ cold formed steel floors

The paper examines the composite performance of hybrid steel‐timber lightweight floor assemblies incorporating cold‐formed steel (CFS) profiles and plywood (PW) flooring panels with varying degrees of shear connection achieved by means of self‐drilling screws. Material, push‐out, and three‐point short‐span floor tests with or without web openings were carried out. The results and observations from the tests provide a detailed insight into the inelastic properties and ultimate response of such floor systems. Push‐out tests indicate that denser connector arrangements increase connection stiffness, while push‐out and short beam tests suggest an optimum connector spacing equal to the beam depth for a balance between structural performance and constructability. The experimental observations indicate that the ultimate condition of the short composite beams was characterized by CFS web crippling under the load application point, followed by a pull‐through of the self‐drilling screws. Web openings reduced the strength of the floor elements compared to the members with full webs. Complementary numerical studies are undertaken using nonlinear finite element procedures which were validated against the beam tests, offering a detailed insight into the stress levels in the timber, steel, and connectors. Codified procedures for determining the capacity of composite CFS sections are compared with the test results, and guidance for the practical design and construction of such systems is given.