Wind-induced vibration control for tower cranes based on a rear-mounted, mass-sharing bi-directional tuned mass damper

This study introduces a novel bi-directional tuned mass damper (Bi-TMD) for tower cranes that is rear mounted and shares mass with the counterweight, overcoming the spatial and structural limitations of conventional designs. Unlike traditional top-mounted or mid-tower dampers, the proposed Bi-TMD is integrated into the counterweight, where movable masses on spring–damper units replace a portion of the concrete ballast. This design preserves the crane's lifting capacity while enabling bi-directional control of both sway and torsional vibrations. Finite-element simulations under Kaimal-spectrum fluctuating wind loads (ANSYS, 21 m s−1) show that the Bi-TMD, with a 5 % modal mass ratio, reduces peak tower-top acceleration and displacement by approximately 49 % and 24 %, respectively. Parametric studies yield three key findings: (1) the counterweight-mounted TMD provides effective vibration suppression, particularly for along-wind sway, without compromising structural integrity; (2) an optimal modal mass ratio of 3 %–4 % maximizes control efficiency and avoids local resonance, especially under cross-wind conditions; and (3) the rear-mounted Bi-TMD achieves 75 %–91 % of the performance of a mid-mounted TMD while avoiding spatial interference at the tower head. These results demonstrate that the Bi-TMD is as a practical and scalable solution for retrofitting existing cranes and for use in space-constrained environments.