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Bi‐tuned semi‐active TMDs: Multi‐hazard design for tall buildings using gradient‐based optimization

Current research on tall buildings design has shown the need for multi‐hazard approaches in numerous practical cases. To improve the performance under hazard‐related horizontal loads, supplemental damping devices emerge as an efficient solution. For example, passive tuned massive dampers (TMDs) have been used in tall buildings for decades. However, since earthquakes and winds mobilize the structures in different ways, the multi‐hazard design of TMDs remains a difficult task. Thus, adaptive devices are an encouraging solution for this purpose. This research proposes an efficient use of existing semi‐active TMDs that were proposed for other purposes through tuning them exclusively to two sets of frequency and damping ratio: a set for seismic loads and a set for wind loads. These bi‐tuned STMDs would behave as passive dampers during any hazard event, but with an appropriate tuning. Because mechanical properties switch only at the beginning and at the end of seismic events, the control system required would be simple and reliable. An optimization‐based methodology is proposed to design multiple BSTMDs. The total added mass is minimized, while the building life‐cycle cost (LCC) is selected as a performance constraint. An efficient gradient‐based algorithm, originally developed for passive TMDs, is adapted for BSTMDs. Two problem formulations are proposed, to allow distinct design alternatives. The devices design is illustrated by four case studies. The examples show that BSTMDs may provide the same performance of their passive counterparts, using less than half of their total added mass.