Shear strengthening of precast prestressed I‐girders using carbon fiber reinforced polymers and in‐fill concrete blocks

Abstract

Due to the rapid increase in traffic volumes, existing infrastructure demands proper assessment and in some cases rehabilitation is needed. Prestressed concrete (PC) I-shaped girders are widely used in prefabricated girder bridges. With sequel generations of shear design provisions their shear capacity might need to be increased in the framework of assessing safety of aging bridges. Earlier attempts in shear strengthening this specific type of girder with fiber reinforced polymers (FRP) has shown early debonding along the concrete surface at the web-flange corner so that the increase in shear strength was very limited. This study presents the results of full scale PC I-girders strengthened with CFRP through epoxy bonded concrete in-fill blocks that locally transforms the I-section to a rectangular section at the position of CFRP strips. This transformation eliminated the early debonding of CFRP shear reinforcement and for the studied configurations a 30%-40% increase in shear capacity was obtained with respect to the unstrengthened control specimen, without and with additional CFRP spike anchors, respectively. In comparison, similar configurations without in-fill blocks reached 5% and 12% increase in shear capacity, respectively. As such, the use of in-fill blocks appeared more effective than local anchorage of the CFRP at the web-flange corner. Analytical verification of the experimental results confirmed that existing formulations lack ability to predict the shear capacity of strengthened I-girders, and further work is needed in this respect.

Shear Strengthening of Precast Prestressed Bridge I-Girders Using Shape Memory Reinforcement

“…This is due to straightening of the fibers and subsequent early debonding around the web-flange corner resulting in pronounced underutilization of the CFRP when applied directly to the I-shaped concrete surface. An alternative technique (recently investigated by the authors) uses concrete in-fill blocks to transform the I-shape into a rectangular shape, with CFRP strips bonded over the in-fill blocks and anchored in the compression flange [10]. This technique illustrated great potential by resisting, for the tested configuration, an additional shear load up to 40%.…”