Upgrading the hanger resistance of RC inverted T-girders using externally bonded carbon fiber reinforced polymers (EB-CFRP)

Abstract

In modern bridges, inverted T-girders are considered the most popular structural solution for supporting longitudinal precast stringers. Nevertheless, they often experience a prevalence of cracking at the web-flange connection, leading to hanger failure. So, in many instances, such elements are in urgent need of being strengthened to keep up with the ongoing increases in traffic loads. Therefore, this paper investigates the effectiveness of externally bonded carbon fiber reinforced polymers for strengthening such girders. Eight third-scale specimens, including an un-strengthened reference one, were cast and tested under monotonic 4-point loading up to failure. Two arrangements were used, namely, continuous sheets (U-wrapped or side-bonded) and discontinuous strips. The sheet's height as well as the strip's centerline spacing were changed as key parameters. Based on the experimental results, it was mainly found that the externally bonded carbon fiber reinforced polymers strengthening technique was effective in increasing the hanger resistance and ductility of the inverted T-girders by roughly 1.37 and 1.42 times, respectively. Moreover, the initial stiffness and energy dissipation of the strengthened specimens were found to be considerably higher than the reference specimen by an average of 60% and 159%, respectively. In addition, by increasing the sheet's height from 200 to 400 mm, the contribution of the strengthening system to the hanger capacity was almost doubled. As for the strip's centerline spacing, it is advised that the strengthening strips be applied as close as possible to the loading locations because of the nonlinearity of their strain distribution. Finally, a model to predict the hanger capacities of the strengthened inverted T-girders was built and agreed well with the experimental capacities obtained during the tests, with an experimental-to-predicted ratio of 1.04 ± 0.03.