Positive and negative moment behaviours of hybrid members comprising cellular GFRP bridge decking epoxy-bonded to reinforced concrete beams

This paper reports tests to failure of hybrid members comprising cellular GFRP decking connected to RC beams via an epoxy adhesive. RC beams of low crack widths under service loads are useful with GFRP decking owing to the economy of and modest expertise needed to install such beams. Key novelties of this investigation include the RC beams (steel, FRP and prestressed concrete beams have been used previously) with the GFRP decking, use of the epoxy-bonded (so chemical, an alternative to mechanical) connection between the GFRP decking and the concrete beams, and study of the positive and negative moment responses (for application to continuous bridges) of this hybrid form. The test results show the adhesive to be a significant deck-to-beam shear connector under positive and negative moments. Whether the deck was a tensile or compressive top chord, the primary failure mode, which occurred at high loads, was delamination within the GFRP at the deck’s flange-to-web joints, and was neither failure of the GFRP-adhesive interface nor of the adhesive between deck units. For the positive moment specimen there was also fracture of the concrete near the deck as observed for FRP-plated RC beams, despite the absence of flexural cracks from this near-deck concrete.