Structural Analysis of Historic Construction – D’Ayala & Fodde (eds) © 2008Taylor & Francis Group, London, ISBN 978-0-415-46872-5 Experimental analysis of rectangular shaped sleeve connectors for composite timber-steel-concrete floors: Bending tests L. Calado, J.M. Proença & A. Panão DECIVIL – Istituto Superior Tècnico de Lisboa, Lisbon, Portugal F.M. Mazzolani, B. Faggiano &A. Marzo DIST – University of Naples “Federico II”, Naples, Italy ABSTRACT: The paper deals with the laboratory tests on timber-steel-concrete composite beams, equipped with an innovative connection system.Tests are part of a more comprehensive experimental campaign, aiming at the evaluation and optimization of the connection devices. In this paper both monotonic and cyclic bending tests on six composite beams are presented. In particular, each specimen consists of a timber beam with rectangular cross section, connected to a concrete reinforced slab by means of steel collars. Specimens differ for the type of collar-timber contact and the collars spacing, in order to determine the more effective solution. The system performance has been evaluated in terms of both maximum force-displacement relationship and accumulated dissipated energy at failure. 1 INTRODUCTION In the context of the restoration of ancient wooden floors, the wood-concrete composite system repre- sents a reliable solution for upgrading existing floor slabs (Gelfi et al., 2002, Mungwa et al. 1999, Giuriani et al., 1998). Such an intervention generally consists of a con- crete thin slab collaborating with the timber beams by means of connectors, like screws, nails, and studs, inserted in the beam by drilling the existing members. In order to avoid any strength reduction of the beams, which could be certainly caused by the perforation for the installation of traditional devices, an innova- tive type of connector has been conceived (Faggiano et al., 2007). It is made up of steel collars, surround- ing the timber beam, which are composed by two or more parts, bolted together at appropriate folded wings, superior wings themselves or purposely welded studs having the function of connectors. At the inter- face between the steel collar and the timber beam, a rubber layer should guarantee the complete adherence between elements. Due to the bolt tightening, the steel sleeves also provide a transversal ringing action on the beam. A comprehensive research activity including both experimental and numerical investigations is ongo- ing in the framework of the international research project PROHITECH (Earthquake Protection of His- torical Buildings by Reversible Mixed Technology). The purpose is the system evaluation in terms of both strength and stiffness and its consequent opti- mization. In particular, experimental tests are carried out on full-scale specimens of ancient timber beams with circular cross sections and new timber beams with rectangular cross sections, at the DIST (Depart- ment of Structural Engineering) of the University of Naples “Federico II” (Prof. F. M. Mazzolani coor- dinator) and at the DECIVIL (Department of Civil Engineering and Architecture) of the Superior Tech- nical Institute in Lisbon (Prof. L. Calado coordinator), respectively. Further experimental tests on full-scale composite beams realized by using the studied steel collars as connection elements are performed at the DECIVIL, with the cooperation of the DIST. The whole experimental investigation includes both mono- tonic and cyclic push-out tests on single connection devices and both monotonic and cyclic bending tests on composite wood-concrete beams, equipped with the sleeve connectors. Numerical analyses on single device were carried out on several configurations, obtained by varying the main parameters which affect the behaviour, such as number of steel parts, both width and thickness of collars and preloading forces in the bolts (Faggiano et al., 2007). Results have allowed identifying the types of collar that supplies the better behaviour, to be used for composite system. In this context, the paper presents the second part of the whole experimental campaign, corresponding to both monotonic and cyclic bending tests on composite timber-concrete beams made of new wood and rectan- gular cross-section, equipped with the selected collars. 817