Experimental investigation on the seismic performance of a novel damage-control replaceable RC beam-to-column joint

The beam-hinge failure modes are recommended in the existing seismic design codes of reinforced concrete (RC) frame systems, to reduce the collapse risk under strong earthquakes. However, the developed plastic hinge at the beam end causes quite a challenge for structural post-earthquake repair. In this study, a novel precast replaceable RC joint in which damages were controlled in the reduced beam section (RBS) steel beam, was proposed for the rapid restoration of structural function. The RBS-based joint (RBSJ) is located in the beam predetermined plastic hinge zone close to the column. To achieve the damage-control objective, the section resistance ratio (β) was defined as the ratio of bending capacity of the non-replaceable section to that of the weakest in RBS beam, which can quantify the flexural strength of the non-replaceable section to that of the RBS. Cyclic tests of six RBSJ specimens with four different β values (1.3, 1.5, 1.8, and 2.0) were conducted to gain insights into their seismic performance. Further, to investigate the behavior of repaired joints, three new RBSJs were subsequently tested with a replaced RBS beam. Test results showed that the proposed RBS-based joint exhibited satisfactory hysteretic behavior, energy dissipation capacity, and replaceability when the β value was larger than 1.3. In addition, the proper increase of β and adding buckling-restrained plates to the flanges of RBS beam could effectively improve the seismic performances of joints.