Compatibility analysis of FRP-strengthened exterior RC beam-column joints: An advanced analytical model

Abstract

Exterior reinforced concrete (RC) beam-column joints are critical components that endure complex stress states during seismic events, often requiring retrofitting due to their vulnerability to shear failure and rebar slippage. However, the complex behavior of these joints has led to significant simplifications in design codes, often neglecting crucial issues such as interactions of rebars, FRP, and concrete, considering rebars' extensions and slippages, FRP sheets' elongations, and other effective parameters such as confinement degree of the joint, FRP stress distribution, and the rebars-to-concrete bond degradations due to cyclic loading. This study addresses these limitations by developing an innovative analytical model for fiber-reinforced polymer (FRP) strengthened exterior RC beam-column joints. The proposed model introduces new compatibility conditions and formulations that comprehensively consider the intricate interactions between externally applied FRP sheets, internal reinforcing bars, and concrete surface deformations. Previous research overlooked these key aspects, leading to difficulty in accurately predicting joint deformations. The proposed model is then simplified for practical applications. To assess the proposed model's accuracy, a comprehensive database is compiled from previous studies, followed by a critical comparison between experiments and the model's estimations and comparisons with established codes for FRP strengthening. The proposed model estimates the joints' shear resistance effectively, with a mean value (MV) of 0.94 and a coefficient of variation (COV) of 12%, surpassing existing codes, which have MV values of 0.26–0.72 and COV values of 83%–148%, respectively.