Keywords: bond-slip, beam element, cyclic loading, hysteresis model, composite beam, shear connector, non-linear analysis.

A composite beam structure, which is constructed by placing a concrete slab on the steel or concrete girders equipped with shear connectors, is a very widely used structural system. However, the composite structure shows partial composite behaviour inducing the bond-slip deformation along the interface of the slab and the girder and, the structural response is different from those when assuming a full composite behaviour.

Much analytical and numerical research concerning the slip behaviour of composite structures were performed. However, it was very hard to apply the proposed analytical methods into the finite element analysis and, numerical analysis based on a double-node concept resulted in a complex mesh definition and sometimes locking problems [1].

Furthermore, the slip behaviour along the material interface becomes clearer with the increase of applied load. Therefore, it is also necessary to evaluate the characteristics of structural behaviour when the deflections are in the in-elastic range such as severe loading conditions including seismic loading or highly reversed cyclic loading. Although much research concerning shear connectors were performed and models which describe the load-slip behaviour of shear connectors were proposed [2,3,4], there are few cases in which the total structural behaviour of composite bridges with shear connectors considering the slip effect is analysed under severe cyclic loadings.

So, the extension of an existing finite element slip model [1], which can consider the partial composite action using a simple beam element with two nodal displacements (without adopting double-node concepts) for application to the composite structures under arbitrary cyclic loading conditions is the purpose of this paper. In this study, incremental slip analysis adopting a non-linear cyclic load-slip relation is performed. In addition to the cyclic load-slip relation, hysteresis models of concrete and steel are applied and, a unique iteration method finding converged status considering the double neutral axis of the section with slip effect is proposed also. The structural responses are analysed by applying the extended finite element based slip model into a composite structure subject to cyclic loadings and, the applicability of the model is verified by comparing the analysis results with published experimental results [5].

1

H.G. Kwak, J.W. Hwang, "FE model to simulate bond-slip behavior in composite concrete beam bridges", Computers and Structures, 88(17-18), 973-984, 2010. doi:10.1016/j.compstruc.2010.05.005

2

A.L. Ciutina, A. Stratan, "Cyclic Performances of Shear Connectors", In "Composite Construction in Steel and Concrete VI", ASCE, 2008.

3

M. Shariati, N. Ramli Sulong, M. Arabnejad K, "Experimental assessment of channel shear connectors under static and fully reversed cyclic loading in high strength concrete", Materials and Design, 34, 325-331, 2012.

4

M.R. Salari, "Modeling of bond-slip in steel-concrete composite beams and reinforcing bars", University of Colorado, 1999.

5

K. Takanashi, K. Usagawa, "Behaviors of steel and composite beams at various displacement rates", ASCE Journal of Structural Engineering, 115(8), 2067-2081, 1989. doi:10.1061/(ASCE)0733-9445(1989)115:8(2067)

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