FRP stay-in-place form and shear key connection for FRP-concrete hybrid beams/decks

A novel assembly FRP (fiber-reinforced polymer)-concrete hybrid beams/decks system is proposed and investigated in this paper. The performance of FRP shear key (SK) connector, FRP stay-in-place (SIP) form, and their combination for the FRP-concrete hybrid beams/decks is evaluated. The slip modulus and interfacial shear capacity of SK, SIP and their combination were investigated via push shear tests with thirteen specimens and four-point bending test with three FRP-concrete hybrid beams. Push-out test results showed that SK has the same shear capacity level and about ten times the slip modulus compared with steel bolt (SB). The cross section of SK is not a significant parameter because all of the shapes can enhance nearly full composite action between the FRP girder and concrete block. SIP can supply a strong initial natural bond with concrete and substantially save the form for concrete casting. This connection-form system combines the SB, SK and SIP as a structurally optimized design of shear connection and the permanent form. The beam test revealed that this connection system supplied full composite action till the failure of the FRP girder. Deflection of the FRP-concrete beam with the novel system can be predicted using equations based on the full-composite action assumption.