HPFRC Jacketing of non seismically detailed RC corner joints

In this article, the effectiveness of a High-Performance Fiber-Reinforced Concrete (HPFRC) jacket for the seismic retrofitting of existing RC corner beam-column joints is experimentally investigated. The results of cyclic experimental tests on full-scale corner beam-column sub-assemblies (two unretrofitted and two retrofitted) are presented and discussed in detail, focusing on the effectiveness of the adopted retrofitting technique. The RC test units were designed with structural deficiencies typical of the Italian construction practice of the 1970s: use of smooth bars, inadequate reinforcement detailing, such as lack of stirrups in the joint panel, and hook-ended anchorage. The results underlined that the joint panel strength impairs the seismic response of the sub-structure with a drift at incipient collapse not greater than 2%. The results showed that the application of thin HPFRC jackets appears a promising technique to strengthen poorly-detailed RC joints: the jacket was able to increase the shear strength of the joint by about 40%, with respect to the bare joint, limiting the damage of the retrofitted sub-assembly, which reached an ultimate drift of 6%.