Assessment of Ductility Indices in FRP-Strengthened RC Beams: A Statistical Analysis

The study aims to use statistical analyses to identify the optimal ductility indices that can characterize the behavior of FRP strengthened RC beams and assess the effects of the longitudinal reinforcements, expressed as total equivalent steel ratio (TESR%). The analyses are based on various techniques such as MANOVA, MANCOVA, and the Johnson-Neyman method. The results showed a significant relationship between TESR% and ductility indices at different levels of the moderator (stirrup ratio). The TESR% has a wide range of negligible regions on Naaman and Jeong's ductility index (0.74% to 1%) compared to Davies's and Oudah (0.72% to 0.87%) and El-Hacha's indexes (0.74% to 0.89%). Therefore, it appears that Naaman and Jeong's index may not provide an accurate assessment for RC beams strengthened by FRP material. The Oudah and El-Hacha index values are greater than those of other ductility indices due to the deformability ratio considered in the calculation. However, Davies's index was more sensible than the other two ductility indices due to its lower values.