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PROCEEDINGS OF THE THIRTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: B.H.V. Topping and Y. Tsompanakis
Nonlinear Elastic-Plastic Analysis of Composite Steel-Concrete Members
Y.-L. Pi1, M.A. Bradford2 and W. Qu3
1Center for Built Infrastructure Research, Faculty of Engineering and Information Technology, University of Technology, Sydney NSW, Australia
Y.-L. Pi, M.A. Bradford, W. Qu, "Nonlinear Elastic-Plastic Analysis of Composite Steel-Concrete Members", in B.H.V. Topping, Y. Tsompanakis, (Editors), "Proceedings of the Thirteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 52, 2011. doi:10.4203/ccp.96.52
Keywords: composite steel-concrete member, elastic-plastic analysis, finite element, nonlinear, slip, interface.
Finite element (FE) methods including force-based and displacement-based formulations have been developed by a number of researchers and used in investigations of composite steel-concrete members . The advantage of force-based formulations is that force interpolation functions are related to the exact solutions of the governing equations of equilibrium of an element that can be selected for the formulation. However, most force-based formulations use force interpolation functions based the solutions from the governing linear differential equilibrium equations. Because of this, it is difficult to find force interpolation functions for the interaction between the nonlinear displacements and the internal forces. Displacement-based formulations have been focused on the slip arising from the partial interaction between the steel and concrete components. Hence, effects of the slip on strains, stiffness, and strength of composite members have often not clearly been demonstrated by these types of models. These displacement-based formulations often deal with small displacement problems only. They are also prone to the problem of curvature locking , that can occur with a large stiffness of the shear connection.
In addition, in the nonlinear range, the interaction between the slip and in-plane bending will produce additional shear strains and stresses at the interface and cross-section. These shear strains and stresses have not been addressed in the open literature. The shear stresses play a role in local yielding and so they should be considered in the FE model.
A total Lagrangian finite element model for the nonlinear analysis of composite steel and concrete members is presented in this paper. Geometric and material nonlinearities and the partial interactions between the steel and concrete components are considered in the formulation. The deformations are considered to consist of a translation and rotation of cross-section, and a slip between the steel and concrete components. The slip is treated as an independent displacement and its interaction with the in-plane bending and effects on strains are derived. Material nonlinearities of concrete include the compression, crack detection, tension stiffening of the cracked concrete, and residual stiffness of the crashed concrete. The comparisons with experimental results have demonstrated that the FE model is efficient, effective and accurate.
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