Experimental study on joints and flexural behavior of FRP truss-UHPC hybrid bridge

This paper presents an experimental study on a fiber reinforced polymers (FRP) truss-ultra-high performance concrete (UHPC) hybrid bridge. Firstly, push-out tests on bolted FRP-UHPC connections revealed steel bolts can supply strong FRP-UHPC composite action. Then, single- and double-lap shear tests on FRP joints showed bolted-bonded joints have smaller slip at the initial loading phase than bolted joints. Finally, a full-scale FRP truss-UHPC hybrid bridge model with one bolted side and the other bolted-bonded side in FRP joints, was tested under varies loading scenarios. The salient findings are: (i) the bridge model can withstand static road load in Chinese bridge specification; (ii) the responses of the FRP members and UHPC slab stayed at the elastic-linear stage under the load of 200 kN and only about 10% of the ultimate strain was reached; (iii) slips between concrete slab and upper FRP chords stayed below 0.36 mm, which shows the steel bolts transferred loads well; (iv) the bolted side had a 26.08% larger deflection than the bolted-bonded side, which validates the findings in shear tests; and (v) the deflection, instead of the stress of FRP members and UHPC slab, is the governing factor of the design of this hybrid systems.