Size Effect on Shear Resistance Capacity of GFRP Rebar‐Reinforced I‐Shaped UHPC Beams Without Stirrup

ABSTRACT The study investigated the shear behavior of I‐shaped ultrahigh‐performance‐concrete (UHPC) beams without stirrups, focusing on the influences of longitudinal reinforcement types, steel fiber content, and size effects. It was found that glass‐fiber‐reinforced‐polymer (GFRP) rebar‐reinforced UHPC beams demonstrated improved ductility and shear toughness index compared to steel rebar‐reinforced beams. Additionally, increasing the steel fiber content can greatly enhance the ductility, shear resistance, and shear toughness index of the concrete beams. Moreover, the shear strength of concrete and shear toughness index of the beam increase as the beam height decreases. However, medium beams generally have lower ductility than large beams, while small beams display greater ductility than both medium and large beams. In the comparison of the shear resistance capacity of beams obtained through experimentation with analytical results based on the guidelines from ACI 318‐19, SIA‐2052, and Eurocode 2, it was observed that the analytical results tended to be overly conservative. JIN et al.'s model provided a closer average prediction compared with the test results, yet the standard deviation was significant. To improve the accuracy of these predictions, this study proposed modifications to JIN's model by considering the impact of different types of longitudinal reinforcement.