Testing of hybrid FRP composite beams in bending

This paper presents tests where hybrid composite beams have been investigated. The hybrid beam consists of a glass fibre I-beam with carbon fibre strengthened bottom flange and a rectangular concrete block in the compressive zone. The interaction between the concrete and composite beam were obtained in two ways; casting in shear connectors of steel and bonding by epoxy adhesive. As a reference, a beam without concrete in the compressive zone was also tested. The idea of combining carbon, glass and concrete was to utilize the stiffness contribution from the carbon and the compressive strength from the concrete. The glass fibre I-beam would then take up the main part of the shear force. The results from the test showed that a good composite action could be achieved between carbon, glass and concrete. However, it could also be noticed, as expected, that an I-beam is not the ultimate form due to stability problems. In the tests, problems arose due to lateral instability, but this was solved by placing stiffeners manufactured from wood between the flanges of the Fibre Reinforced Polymer beam over the supports. With a few modifications of the hybrid beam it is believed, that it would be possible to create both a technical and economical hybrid profile that benefits from carbon, glass and concrete. (C) 2004 Elsevier Ltd. All rights reserved.