External strengthening of RC structures with buckling-restrained braced frames

In this study, four 1/2-scaled, 3-dimensional, 2-story, deficient reinforced concrete (RC) specimens were examined by applying reverse static-cyclic excursions. Among the specimens, one served as a reference frame, and the others were externally strengthened using buckling-restrained braced steel frames (BRBFs). Anchorage rods were used to connect the BRBFs to the RC specimens. Thus, the RC structure transferred lateral loads to the BRBFs through these rods. The BRBFs, as a novel lateral load-carrying mechanism, were able to withstand the lateral demands placed on the deficient RC structure. New foundations were constructed adjacent to the existing foundations of the RC specimens for the BRBFs. Anchorage rods were used to connect them also. In this way, both foundations carried forces induced by steel and RC members with anchorage rods. As long as the structural RC elements remained in elastic or limited plastic regions, BRBFs enhanced the rigidity, energy absorption, and load-bearing capacity of existing deficient RC buildings. Thus, the strengthened RC specimens were effective at resisting the lateral demands as well as the self-weight and dead loads on them. Numerical analyses were also carried out, and the performance criteria for strengthened RC specimens were discussed in addition to the experimental studies. Design proposals were presented for the exterior upgrading of RC buildings with BRBFs and their foundations.