Engineering Structures 31 (2009) 1369–1381 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct Flexural behaviour of multi-span GFRP-concrete hybrid beams João R. Correia * , Fernando A. Branco, João G. Ferreira Civil Engineering and Architecture Department, Instituto Superior Técnico - ICIST, Technical University of Lisbon. Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal article info Article history: Received 14 July 2008 Received in revised form 16 September 2008 Accepted 2 February 2009 Available online 28 February 2009 Keywords: Fibre reinforced polymers Glass-reinforced plastics GFRP pultruded profiles Pultrusion Concrete Shear connection Composite beams Composite structures abstract This paper presents results of an experimental and analytical study on the flexural behavior of multi- span GFRP-concrete hybrid beams. Previous investigations showed the viability and technical advantages of connecting GFRP pultruded profiles to concrete elements in GFRP-concrete hybrid cross-sections, used in simply supported structural elements. The objective of the present study was to investigate the flexural behaviour of the GFRP-concrete hybrid solution in continuous structural elements, in which, in addition to the lower deformability when compared to isostatic systems, the cross-sectional and structural redundancies may also allow for a certain pseudo-ductility at failure. With this purpose, a set of design equations was derived in order to analyse the flexural behaviour of continuous hybrid beams, subjected to positive and negative bending. Those equations were used to design two continuous 3-span and 2-span hybrid beams with a bonded shear connection system, which were tested in bending. The flexural tests allowed us to investigate the serviceability behaviour and the failure mechanisms of multi- span GFRP-concrete hybrid beams. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Glass fibre reinforced polymer (GFRP) pultruded profiles have significant potential for use in civil infrastructure, owing to their several advantageous properties when compared to traditional materials. These advantages include high strength, lightness, free formability, ease of installation, good thermal and electro- magnetic insulation properties, low maintenance requirements and resistance to corrosion and fatigue [1]. Initially used mainly in non-structural elements or in secondary structures, in the last few years, GFRP pultruded profiles have found an increasing number of applications in primary structures of bridges and buildings, in both the rehabilitation of degraded structures and in new constructions [2–6]. Despite those several advantageous properties over traditional materials, GFRP profiles also feature some technical disadvantages. The most important structural constraints are associated with the lack of material-adapted structural shapes, the relatively low elasticity modulus, the brittle behaviour and the susceptibility to instability phenomena, which prevent the full exploitation of the GFRP material properties. Previous investigations reported by Deskovic et al. [7], Hall and Mottram [8], Canning et al. [9], Fam and Rizkalla [10], * Corresponding author. Tel.: +351 218 418 212; fax: +351 218 488 481. E-mail address: jcorreia@civil.ist.utl.pt (J.R. Correia). Hullat et al. [11], Seible et al. [12], Correia et al. [13,14] and Keller et al. [15] showed that one way to make a better use of the GFRP profiles’ material is by connecting them to concrete elements in GFRP-concrete hybrid elements. The several hybrid concepts proposed by the different authors aimed at combining the directional behaviour, the lightness and high mechanical performance of FRP materials, with the most relevant properties of traditional materials, particularly with concrete, a less expensive and more massive material. Such a combination, typically conceived and tested in simply supported structural elements, led to solutions that are particularly useful for the rehabilitation of old floors and also for new construction, resulting in a synergetic increase of both stiffness and strength. Based on previous investigations carried out at IST on the use of GFRP-concrete hybrid cross-sections in simply supported structural elements [13,14], this paper presents results of a further study on the behaviour of a GFRP-concrete hybrid solution in continuous structural elements. With this purpose, a set of design equations was derived in order to analyse the flexural behaviour of hybrid beams subjected to negative bending. Those equations, together with a previously presented analytical formulation for positive bending [13], were used to design two continuous 3-span and 2-span hybrid beams comprising a bonded shear connection system, which were tested in bending. The flexural tests allowed us to investigate the serviceability behaviour and the failure mechanisms of continuous beams submitted to negative (and positive) bending moments. 0141-0296/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.engstruct.2009.02.004