Seismic retrofit of exterior RC beam-column joints with bonded CFRP reinforcement: An experimental study

This paper presents an experimental study on the strengthening of seismically deficient RC beam-column joints using carbon fiber reinforced polymer (CFRP). Six exterior RC beam-column joint specimens were tested to identify an effective method for improving the seismic performance of such joints in terms of their lateral strength and ductility. These six specimens included one non-seismically designed specimen, one seismically designed specimen, and four specimens retrofitted using different schemes. In these schemes, both externally bonded CFRP sheets and near-surface mounted (NSM)CFRP strips were explored as strengthening options. The test results showed that by adding CFRP reinforcement, the seismic performance of a seismically deficient beam-column joint can be significantly improved. In particular, the use of NSM CFRP strips in beams and joints was found to effectively relocate the plastic hinge away from the joint region, thereby leading to a ductile failure mode (beam flexural failure), which demonstrates the effectiveness of this seismic retrofit method. A good understanding of the hinge relocation mechanisms has been achieved through extensive and detailed strain measurement during the tests.