Fiber Orientation in Ultra-High-Performance Concrete Shear Keys of Adjacent-Box-Beam Bridges

摘要

This paper presents an investigation of the fiber orientation within a field-cast reinforced ultra-high-performance concrete (UHPC) shear key replica. To simulate field conditions, replica shear key forms were constructed to be identical to keys of an adjacent box-beam bridge undergoing construction at the time of the research. The replica keys were then placed on site along with the actual keys of the constructed bridge. Cores were taken from the replicas and analyzed using a micro-computed tomography (micro-CT) method to determine the fiber orientation. Fibers tended to align parallel to the flow direction, except in shear reinforcement locations and at the shear key wall. Regions with higher fiber density were found on the upstream side of the shear reinforcement, while low-fiber regions were found immediately downstream of the reinforcement. Finite element analysis of a core revealed an increase in the stresses within the UHPC matrix in the low-fiber region due to pullout of a shear reinforcement bar.