Journal of Constructional Steel Research 67 (2011) 308–321 Contents lists available at ScienceDirect Journal of Constructional Steel Research journal homepage: www.elsevier.com/locate/jcsr Full-scale long-term experiments of simply supported composite beams with solid slabs Safat Al-deen a , Gianluca Ranzi a,∗ , Zora Vrcelj b a School of Civil Engineering, The University of Sydney, Sydney, NSW 2006, Australia b School of Civil and Environmental Engineering, The University of New South Wales, Sydney, NSW, Australia article info Article history: Received 2 July 2010 Accepted 5 November 2010 Keywords: Composite beam Creep Partial shear interaction Shrinkage Serviceability abstract This paper presents an experimental 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 solid concrete slab. Three full-scale simply supported beams with identical spans and cross-sections were prepared and tested. These specimens were designed as secondary beams of a typical composite flooring system based on Australian guidelines with the lowest permitted level of degree of shear connection of 0.5. They were cast simultaneously to enable comparisons with respect to pouring and loading conditions. One beam was cast un-propped and was kept unloaded for the whole duration of the long-term tests to measure shrinkage effects. The remaining two beams, cast under un-propped and propped conditions, respectively, were subjected to a sustained uniformly distributed load. Standard short-term and long- term tests were carried out to obtain the relevant material properties of both the steel and the concrete. Short-term 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 a step-by-step procedure, while the steel joist and reinforcement were assumed to remain linear elastic. Two constitutive relationships were adopted for the shear connection, i.e., a linear-elastic one, and a new time-dependent one, to account for the long- term effects produced in the complex stress state of the concrete surrounding the shear connectors. The latter representation is intended to fall within the framework of simplified approaches suitable for design applications. Considerations of the accuracy of the numerical predictions are presented based on the two shear connection models. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction Composite steel–concrete beams represent an economical structural solution for building and bridge applications. The composite action is provided by the presence of mechanical devices. These are commonly specified in the form of shear connectors, which are welded to the top flange of the steel joist and embedded in the concrete slab during casting. This structural solution is efficient when subjected to sagging moments, taking advantage of the ability of concrete and steel to perform well in compression and tension, respectively. Modern building construction adopted in Australia tends to produce design solutions in which serviceability is often the governing limit state in composite floor systems, either due to excessive total or incremental deflections, or due to undesired ∗ Corresponding author. Tel.: +61 2 9351 5215; fax: +61 2 9351 3343. E-mail addresses: gianluca.ranzi@sydney.edu.au, G.Ranzi@civil.usyd.edu.au (G. Ranzi). dynamic responses. This paper is concerned with the case in which the serviceability limit state governs the design due to excessive deflections, which occur due to creep and shrinkage of the concrete. When dealing with the time-dependent behaviour of concrete, there are two main factors to be addressed: (i) the definition of adequate constitutive relationships (i.e., a material property problem); and (ii) the use of methods of analysis capable of handling the structural response over time (i.e., a structural analysis problem) [1,2]. Early work on the modelling of composite beams highlighted the importance of accounting for the deformability of the shear connectors within the framework of partial interaction theory; see, e.g., [3]. This initial formulation is usually referred to as the Newmark model. Since then, extensive work has been carried out relying on this model or extending its applicability. For example, some of these studies have focussed on the linear-elastic response of composite beam–columns (e.g., [4–6]), the shear deformability of the steel joist (e.g., [7,8]), the derivation of analytical and numerical models to predict the time-dependent behaviour of composite members (e.g., [9–13]) and related finite element (FE) 0143-974X/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jcsr.2010.11.001