Use of semi-active tuned mass dampers to control footbridges subjected to synchronous lateral excitation

Abstract

Tuned mass dampers (TMDs) have been an extensively used technology to control harmonic induced vibrations. These devices have been successfully employed in a wide range of applications, with particular focus on the areas of civil and mechanical engineering. The control of the synchronous lateral excitation in footbridges has been a recent concern, with the use of TMDs being one of the most employed solutions to mitigate this problem. However, this type of devices is very sensitive to the tuning properties and exhibits a clear performance downgrade when detuning occurs. By adding a semi-active damper in the connection between the structure and TMD, it is possible to mitigate the detuning effect, making this feature one of the most interesting advantages of semi-active tuned mass dampers (SATMDs). In this paper, the application of SATMDs to control synchronous lateral excitations in footbridges (also known as ‘lock-in’) is addressed. A numerical procedure is proposed to evaluate its effectiveness and to compare it to passive TMDs. Two example structures are studied: the first corresponds to a practical example of a footbridge with one mode of vibration, which represents a common scenario in footbridge design; the second is a real footbridge with three modes of vibration within the critical lateral resonance range. The results demonstrate a higher efficiency for the SATMD when compared to passive TMDs, particularly regarding to the lower detuning sensitivity, which leads to a substantially lower inertial mass of the device.