Conventional seismic assessment of reinforced concrete (RC) frames retrofitted with externally bonded carbon fiber–reinforced polymer (CFRP) typically relies on quasi-static force–deformation metrics, overlooking the frequency-dependent evolution of energy dissipation. This study investigates the effects of excitation frequency and CFRP detailing system on the dynamic response of retrofitted frames using an energy-based framework and the equivalent viscous damping ratio (EVDR). A three-story RC frame was subjected to harmonic base displacement over a range of frequencies and evaluated using two CFRP retrofit configurations at beam plastic hinges: an extended flange-bonded CFRP sheet configuration and a configuration designed to promote plastic hinge relocation. Results show that, at resonance, the extended flange configuration increased elastic energy by 67% and reduced hysteretic damping by 40%, leading to excessive force amplification that compromised cyclic endurance. In contrast, the hinge relocation configuration limited elastic energy growth to 30%, maintained higher hysteretic damping, and improved cyclic endurance. Moreover, CFRP retrofitting was most effective below resonance and became progressively less effective at higher excitation frequencies. These findings underscore that effective CFRP retrofit design must jointly consider the targeted excitation frequency and CFRP detailing system to optimize energy dissipation and structural resilience.
