Seismic retrofit and strengthening of reinforced concrete moment frames with strongback-braced system

Using the steel strongback braced (SB) system to seismically strengthen and retrofit reinforced concrete moment frames (RCMFs), this research aims to enhance the effectiveness of RCMFs. In this study, RCMFs of 5-, 10-, and 15-stories were designed according to the first and fourth editions of the Iran Earthquake Standard 2800. The RCMFs designed for the first edition are strengthened and reinforced using the strongback braced system. The studied structures were analyzed under incremental static loading and time history analysis. The findings indicate that the yield force and maximum base shear of structures designed using the fourth edition have increased by a range of 1.28–1.42 compared with those designed with the first edition. This underscores the imperative to enhance the structural integrity of buildings constructed according to the first edition. Meanwhile, the results of retrofitted structures with strongback braces show the same or better performance than newly designed structures. This indicates that this retrofitting system has a favorable effect on uniform drift control. A reduction of 33%–44% in story drift was observed when the SB system is added to the first edition’s structure.