SEISMIC RETROFITTING OF CHEVRON-BRACED STEEL FRAMES BASED ON PREVENTING BUCKLING INSTABILITY OF BRACES

In this research, a seismic retrofitting method for chevron-braced frames (CBFs) is proposed. The key idea here is to prevent the buckling of the chevron braces via a conventional construction technique that involves a hysteretic energy-dissipating element installed between the braces and the connected beam. The energy-dissipating element is designed to yield prior to buckling of the braces, thereby preventing the lateral stiffness and strength degradation of the CBF caused by buckling, while effectively dissipating the earthquake input energy. Nonlinear static pushover, time history and damage analyses of the CBF and retrofitted CBF (RCBF) are conducted to assess the performance of the RCBF compared with that of the CBF. The results of the analyses reveal that the proposed retrofitting method can efficiently alleviate the detrimental effects of earthquakes on the CBF. The RCBF has a more stable lateral force-deformation behavior with enhanced energy dissipation capability than the CBF. For small-to-moderate intensity ground motions, the maximum interstory drift of the RCBF is close to that of the CBF. But, for high intensity ground motions, it is considerably smaller than that of the CBF. Compared with the CBF under medium-to-large intensity ground motions, the RCBF experiences significantly less damage due to prevention of buckling of the braces.