Experimental study on flexural behavior of hollow steel-UHPC composite bridge deck

• Excellent bending capacity and material utilization can be achieved in the novel hollow steel-UHPC composite deck. • The effects of the embedded steel tubes, steel bars, UHPC material, and flange thickness on the mechanical properties of hollow steel-UHPC composite decks are discussed. • There is a great composite effect between the embedded steel pipe and the UHPC without any additional shear connection. • A theoretical formula is proposed to predict the flexural capacity of the hollow steel-UHPC composite deck. The application of UHPC might reduce the weight of the bridge deck and improve its crack resistance and durability. This study proposes a hollow steel-UHPC composite deck composed of the hollow steel tube and UHPC without shear connectors. The flexural test was performed on the hollow steel-UHPC composite deck to evaluate the effects of the embedded steel tubes, steel bars, UHPC material, and flange thickness. In addition, the mechanical properties of hollow steel-UHPC composite decks were compared with waffle decks and solid concrete decks. Results indicated that the hollow steel-UHPC composite deck had excellent bending capacity and material utilization. The load-deflection curve of the composite decks could be divided into four stages: elastic stage, working stage with cracks, nonlinear stage, and fully plastic stage. Without any additional shear connection, the steel-UHPC interface slip did not occur until the load reached 0.89 P u . In the ultimate limit state, the strains at the mid-span cross-section of steel and UHPC were almost the same, suggesting that there was a good composite effect between the embedded steel tube and the outer UHPC. The embedded steel tube had a significant influence on improving the original stiffness ( K 0 ), the stiffness at the working stage with cracks ( K 1 ), and the flexural capacity ( P u ) of composite decks. The flexural failure of the hollow steel-UHPC composite deck was controlled by the tensile zone. Finally, a theoretical formula was proposed to predict the flexural capacity of the hollow steel-UHPC composite deck.