Project description

Externally bonded fiber-reinforced polymer (FRP) jacketing has gained popularity in strengthening reinforced concrete (RC) columns because of its ease of application compared to enlarging the section of concrete columns by casting concrete or installing steel tubes. While FRP jacketing is effective for circular columns, extensive experimental studies have shown that FRP jacketing is much less effective for rectangular concrete columns, as shown in Fig. 1a the typical stress-strain behavior of FRP-confined circular (Mirmiran and Shahawy 1997) and rectangular columns (Pessiki et al. 2001). The reason for the ineffectiveness is the confinement in rectangular columns is nonuniform, and the behavior of concrete under non-uniform confinement is much more complicated than that under uniform confinement. The Co-PI has developed a finite element (FE) model that can accurately predict the behavior of FRP-confined rectangular columns (Zheng and Teng 2023). Fig. 1b shows the FE prediction of axial stress distribution in an FRP-confined rectangular column, where the majority of the section (blue) is under-confined with low axial stress. According to the FE results, the under-confined concrete is subjected to a high confining stress in the direction parallel to the flat side but only a trivial confining stress is achieved perpendicular to the flat side. This stress situation is the cause of the ineffective confinement in rectangular columns. Therefore, the key to effectively confining rectangular concrete columns is to provide confining stress perpendicular to the flat sides. The objectives of the proposed research are: 1) develop a cost-effective and easy-to-apply FRP jacket and anchor system that can effectively confine rectangular columns, and 2) evaluate the effectiveness of the developed FRP jacket and anchor system through scaled concrete column tests.