Research in Progress (ACI Spring 2023, San Francisco, CA) UHPC's inherent anisotropy has two effects on structural members: fiber orientation and fiber distribution. Both effects are impacted by the casting process and the flow pattern and have repercussions on the tensile response of the UHPC structural element. This study provides insight from micro-CT scans on shear tests of UHPC I-shaped beams with heights ranging from 300 to 1150 mm. The UHPC mix had 1.5% steel fibers and it was randomly poured into the beams. A qualitative analysis of the micro-CT images revealed that the issue of fiber orientation is significantly magnified by the fiber distribution as the beam depth increases. In structural elements subjected to shear loading with no structural redundancy, it is complex to depend on the tensile strength of UHPC as a predictor of shear strength. A shear design equation is proposed based on UHPC's compressive strength which has less variation associated with fiber distribution or orientation.

Undergraduate Research Session (ACI Spring 2023, San Francisco, CA) Concrete structures serve an important role in society's infrastructure, and they often include steel reinforcement bars that may be connected via steel couplers to increase tensile strength. However, corrosion of the reinforcing steel can cause unwanted cracking and spalling of concrete, deteriorating the structural member. Nonmetallic components such as GFRP bars and FRP couplers present a solution to this corrosion issue. These bars and couplers have been manufactured, but there is insufficient testing data on their performance under tension as well as research on how to best connect the bars and coupler. The objective of this research project was to evaluate the performance of GFRP bars connected with FRP couplers during tensile testing (Fig. 1). A control tensile test was conducted with steel reinforcing bars and a steel coupler to establish a baseline for performance. Connecting GFRP bars with epoxy couplers was also investigated to expand the range of results. The test results fill an important knowledge gap related to the performance of GFRP bars connected with corrosion-resistant couplers that may be used as a suitable replacement for steel in reinforced concrete structures.