Design Considerations for the Long-Term Behaviour of Composite Steel-Concrete Beams
S. Al-Deen1, G. Ranzi1 and Z. Vrcelj2
1School of Civil Engineering, The University of Sydney, Sydney, Australia
2School of Civil and Environmental Engineering, The University of New South Wales, Sydney, Australia
This paper presents a study aimed at the evaluation of the long-term behaviour of composite steel-concrete beams designed with partial shear connection formed by a steel joist and a concrete solid slab. The results of an experimental programme are presented. Specimens were designed as secondary beams of a typical composite flooring system based on Australian guidelines with the low levels of degree of shear connection. Companion samples were cast simultaneously to enable comparisons with respect to pouring and loading conditions. For each set of samples one beam was cast unpropped and was kept unloaded for the whole duration of the long-term tests to measure shrinkage effects. A corresponding companion sample was cast under unpropped conditions and was subjected to a sustained uniformly distributed load. Standard short- and long-term tests were carried out to obtain the relevant material properties of both steel and concrete. Short and long-term push-out tests were carried out to obtain information on the response of the shear connectors. The experimental results were modelled by means of the finite element method. The time-dependent behaviour was depicted using the step-by-step procedure while the steel joist and reinforcement were assumed to remain linear-elastic. Considerations on the modelling of the shear connection are presented remaining within the framework of simplified approaches suitable for design applications. The accuracy of the numerical predictions is discussed based on the specified material properties and the reported experimental data.
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