Development and Performance of a Composite UHPC Box-Beam Bridge Section

Due to superior mechanical and durability properties, ultrahigh-performance concrete (UHPC) has been increasingly used for bridge systems across the world. The flexural and shear design of UHPC beams has been thoroughly investigated; however, limited research has evaluated the interface shear performance between cast-in-place conventional concrete (CC) decks and UHPC precast beams, particularly when the fluted details are employed. To address this issue, a study was conducted to examine the influence of flute length and flute depth on the interface shear performance of two full-scale UHPC composite box beams. The sections were designed to initiate with interface damage, followed by shear cracking. The interface reinforcement restrained both slip and uplift between the CC deck and the UHPC beam. The interface shear performance of the UHPC composite beam is correlated to the spacing of the flutes rather than the flute length. The shear stress versus slip curve matched well with push-off test results, indicating that the push-off specimens can effectively represent the stiffness of full-scale bridge beams. Predictive formulations provided by the AASHTO UHPC Guide and previous research by the authors are shown to provide a conservative estimate of available interface shear capacity.