Experimental Study on Seismic Behavior of Seismic Damaged RC Frame Joints with T-Shaped Columns Rehabilitated Using Hybrid Fibers–Modified Reactive Powder Concrete

Reinforced concrete (RC) frame joints with T-shaped columns are widely used due to the special cross-sectional shape, which makes the indoor space arrangement flexible. Frame joints with T-shaped columns are more vulnerable to damage under seismic actions. Hence, it is essential for research on their rehabilitation after earthquake damage. To investigate the effectiveness of hybrid fibers–modified reactive powder concrete (HFMRPC) in rehabilitating frame joints with T-shaped columns, in-plane quasi-static loading tests were conducted on four seismic damaged T-shaped column frame joints (i.e., cast-in-situ interior joint and exterior joint, prefabricated interior joint and exterior joint). The tests and analysis results indicated that using HFMRPC for replacement rehabilitation effectively enhanced the bearing capacity, displacement ductility, and energy dissipation of frame joints with T-shaped columns, thereby delaying the stiffness degradation in the late loading stage. Compared with the prerehabilitated specimens, the enhancements in peak load, ductility coefficient, and cumulative energy consumption of the rehabilitated specimens ranged from 10.2% to 26.4%, 22.0% to 47.0%, and 62.2% to 109.8%, respectively. The core area of the rehabilitated specimens exhibited a multicrack development pattern, in which the energy dissipation capacity of the core area was improved. Finally, a flexural capacity calculation method for frame joints with T-shaped columns is proposed based on GB 50367-2013 and JGJ 149-2017.