Recovery resilience framework of replaceable AB-BRB for seismic strengthening during the aftershock stage

Earthquakes cause serious damage to structures, and seismic strengthening is an effective solution to improving structural capacity. With the development of prefabricated technology, the assembled buckling-restrained braces (BRBs) have garnered significant attention in structural engineering due to their potentials to enhance seismic resilience and to guarantee recoverability behavior. At this stage, research on the replaceable performance of assembled BRBs is limited in the current body of literature. The specific focus on the replaceability aspect of assembled BRBs, including the ease of replacing individual components or the entire brace system, has not been extensively explored. Meanwhile, research on earthquake resilience during the aftershock stage is relatively limited at present. Despite the recognition of the significant and prolonged impact of aftershocks on communities and infrastructure, there is a paucity of comprehensive studies specifically focusing on the resilience strategies and measures required during this stage. The authors formerly proposed a novel assembled bolt-connected BRB (AB-BRB), and experiments have been conducted to verify its hysteretic and replaceable behaviors. In this paper, the recovery resilience of the proposed replaceable AB-BRB for seismic strengthening is further assessed, especially during the aftershock stage. The replacement realization of AB-BRB in analysis is first introduced. Then the recovery resilience framework for assessment during the aftershock stage is proposed. Finally an implementary example is given to perform the recovery resilience framework, in which two cases and three scenarios are discussed in detail. In general, after using the ABBRB for seismic strengthening, the recovery time obviously decreases and the resilience index obviously increases when compared with the results in un-strengthened scenario (scenario 3), which demonstrates that the retrofitted system possesses a better resilience recovery capacity. For EEL in case 1, the recovery days are given to be 298.7446 before strengthening (scenario 3), and the results drop to 165.4133 (scenario 1) and 147.0295 (scenario 2) after strengthening. Correspondingly, the resilience index is calculated as 0.5022 before strengthening (scenario 3), and the results increase to 0.7101 (scenario 1) and 0.7411 (scenario 2) after strengthening. Similar conclusions can be given for case 2 and other intensity levels. Meanwhile, after performing the replacement operation of AB-BRB (scenario 2), the seismic performance of the retrofitted system further enhances during the aftershock stage (i.e., less recovery days and larger resilience index). For case 1 and recovery form 1, the resilience index for 1 month is signified as 0.6272, 0.6869 and 0.2066 from scenario 1 to 3, and the resilience index for 3 months is signified as 0.8182, 0.8561 and 0.4965 from scenario 1 to 3. Compared with scenario 1, the recovery ability in scenario 2 is further ensured and the potential risk is further controlled, which demonstrates the importance of replaceable capacity of AB-BRB for resilience improvement especially during the aftershock stage.