Design of Composite Cold-Formed Steel Flooring Systems

Abstract

Recently conducted experimental and numerical investigations have shown that mobilisation of composite action within systems comprising cold-formed steel beams and wood-based floorboards is feasible and can lead to substantial improvements in structural performance. However, no design rules have yet been established for these systems in order to allow the beneficial effect of composite action to be exploited. In this paper, proposals for the design of such systems are devised and their theoretical basis is presented. At the core of the proposals is the calculation of the attained degree of partial shear connection and the shear bond coefficient for the composite members as a function of the geometric and material properties of their components and connectors. The accuracy of the devised design method for the prediction of moment capacity and flexural stiffness is demonstrated through comparisons with the results of 12 physical tests and about 80 numerical simulations reported in the literature. The proposals provide practical design rules for composite cold-formed steel floor beams, which are suitable for incorporation into future revisions of the Eurocodes.

08.09: Design of cold‐formed steel composite flooring systems with partial shear connection

“…Degradation of the moment resistance with high levels of shear can be observed in Fig. 5, where the applied moment M Ed normalised by the moment capacity M c,Rd is plotted against the applied vertical shear force V Ed normalised by the shear resistance V b,Rd for all the physical tests and numerical simulations reported in [3] and [4] respectively. It is evident that an appropriate allowance should be made, accounting for the effect of the design shear force V Ed on the moment resistance M c,Rd .…”

“…spacing of cold-formed steel beams employed for the examined flooring systems is 600 mm. Since the conducted experiments and numerical simulations have shown that there is no shear lag for this spacing [3,4], the effective width of the floorboard b eff can be taken equal to the spacing of the beams (i.e. 600 mm).…”

“…Design expressions are presented for the calculation of the attained degree of shear connection of a system, and for the determination of bending resistance, shear resistance and flexural stiffness (for deflection and vibration checks). The theoretical background of the employed equations is described, and the accuracy of the proposals is assessed against the results obtained from physical tests and numerical analyses reported in the literature [3,4].…”

Composite Behaviour of Cold‐formed Steel ‐ Timber Floors

“…It can also be observed that the experimental flexural stiffness for specimens C-150-A (EIexp = 2823 kN.m 2 ± 4.2%) almost coincides with the analytical flexural stiffness obtained assuming full composite action, indicating that the specimen is nearly fully composite and that a high shear transfer occurs using such connection detail. Table 3 presents predictions of the flexural stiffness of the tested floors derived using existing models in [1], [6] and [9] as well as their deviation from experimental data. For each connection type, the analytical flexural stiffness was determined using results from the average pushout tests (in particular, k0.75).…”

“…Such improvements are influenced by the spacing of shear connectors [3,4], connection detail (e.g. screws or bolts [5] with or without the presence of structural adhesives [3]), span length [6], joist gauge [3], and the type and depth of floor boards [9].…”