Keywords: composite slab, longitudinal slip, ribbed decking, full interaction, ultimate load, load-deflection, failure modes.

This paper described an investigation on the influence of using longitudinal slip model in ribbed decking composite slab in finite element analysis. The current study is based on nonlinear three dimensional (3D) finite element models using ANSYS. Full and partial interaction models have been used to study the influence of slip in the model. The model has been validated using experimental result for accuracy and behaviour trend. Close agreement has been observed between the finite element model and experimental results for ultimate loads and load-deflection response for composite slabs with slip compare to without slip. The analyses also have shown both models fail in different modes. The finite element model with slip was thus found, more accurate to be used in modelling compare to without slip.

In 3D finite element modeling of composite slab system, most of the researchers normally used same nodes for profiled sheeting and concrete [1,2,3,4]. This method will ignore the effect of longitudinal slip in FE model and perfect bonding between steel decking and concrete was assumed. The 3D nonlinear finite element models have been developed to investigate the different of composite slab behaviour under both modelling technique. The models take into account the nonlinear material properties of the concrete and profiled steel sheeting. For slip model, the interaction element between concrete and steel decking has been developed. Combination of spring and link element has been used to simulate the interaction between steel decking and concrete for proposed slip model. For full-interaction model, steel and concrete were used the same node.

Composite slab tests conducted by Wright [5] were used to verify the developed finite element models by comparing ultimate load and load-deflection response. In general, the load-deflection behaviour obtained from FE slip model and FE full-interaction model are agree quite well to the corresponding experimental curves. However, the load-deflection curve behaviour for FE slip model is very close through entire loading range compare to FE full-interaction model. The FE full-interaction model load deflection plot in linear range is slightly less stiff and become stiffer in nonlinear range and seems deviates away from experimental result at the end of applied load. It can be seen that for ultimate load, when compare to experimental result, approximately 4% difference was observe for FE slip model while 10% for FE full-interaction model. Perfect bond between the concrete and steel decking is assumed in FE full-interaction model may cause the higher stiffness in nonlinear range but the assumption would not be true for experimental composite slab. It also can be seen that the main concrete failure mode in FE slip model was shear bond-flexural while for full interaction model was flexural only.

It was concluded that the proposed FE slip model more accurate than FE full-interaction model. The FE slip model has a large extent proved capable of predicting the elastic as well as inelastic load-deflection behaviour of the slab and ultimate loads accurately. It was observed that interaction element proposed here are able to represent the actual behaviour of composite slab. The FE slip model also has capability to show the separation of composite slab and damping coefficient can be included between steel decking and concrete.

1

Kim B., Wright H.D. and Cairns R., "The behaviour of through-deck welded shear connectors: an experimental and numerical study", Journal of Constructional steel Research 1990; 15, pp. 85-255.

2

Ellobody E. and Young B., "Performance of shear connection in composite beams with profiled steel sheeting", Journal of Constructional steel Research. Vol. 62, Issue 7, July 2006, Pages 682-694 doi:10.1016/j.jcsr.2005.11.004

3

Elghazouli A.Y. and Izuddin B.A., "Realistic modeling of composite and reinforced concrete floor slab under extreme loading. II: Verification and application", Journal of Structural Engineering, ASCE, Dec 2004, pp. 1985-1996. doi:10.1061/(ASCE)0733-9445(2004)130:12(1985)

4

Sebastian W.M. and McConnel R.E., "Nonlinear FE analysis of steel-concrete composite structure", Journal of Structural Engineering, ASCE, June 2000, pp. 662-674. doi:10.1061/(ASCE)0733-9445(2000)126:6(662)

5

Wright H.D., "Design of floor decks utilizing profiled steel sheeting and through welded studs", Thesis submitted to the University of Wales for the degree of Doctor of Philosophy, Sept. 1988.

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