Experimental and theoretical investigations of the existing reinforced concrete frames retrofitted with the novel external SC-PBSPC BRBF sub-structures

The experimental and theoretical investigations of the existing reinforced concrete frame (RCF) retrofitted with a novel external retrofitting sub-structure, self-centering precast bolt-connected steel-plate reinforced concrete buckling-restrained brace frame (SC-PBSPC BRBF), are presented in this paper. The sub-structure compositions, specimen design, loading protocol, failure modes, hysteresis curves, strain gauge responses, prestressed tendon variations, and indicator evaluations are introduced specifically based on 4 groups of scaled specimens, and the simplified theoretical analyses are also conducted to compare the results with the experiments. Generally, the experiments verified the feasibility of the novel external retrofitting approach, and the sub-structures were precast and assembled with high efficiency. The failure modes of the existing RCFs were controlled, and the bearing capacities of specimens almost quadrupled after retrofitting. The prestressed tendons reduced the residual deformation and realized the structural SC capacities, while the external braces enhanced the energy dissipating capacities to some extent. The simplified theoretical model of skeleton curves was given based on the modified stiffness, and the equations can be utilized to predict the parameter influences as well as the capacity trends in the future explorations.