Bouc-Wen modelling of asymmetric Stockbridge damper for the wind-induced vibration control of suspension bridge hangers

• A four-degree-of-freedom Bouc-Wen model for asymmetric Stockbridge dampers. • Accurately reproduces amplitude-dependent dynamic behaviour. • Calibrated on laboratory tests of dampers from the Hålogaland Bridge. • Validated against field-recorded multiharmonic excitations. • Outperforms impedance-based methods and embeds into hanger-damper simulations. Stockbridge dampers are traditionally employed in overhead transmission lines, but their application has recently expanded to suspension bridge hangers. In this context, their increased size, asymmetric configuration, vertical installation, and absence of dedicated design standards present new challenges in understanding their dynamic behaviour. Proper characterisation is essential to correctly dimension the device and determine its optimal placement on the structure. This study addresses these challenges by presenting a four-degree-of-freedom nonlinear model of an asymmetric Stockbridge damper using the Bouc-Wen hysteretic formulation to capture the messenger cables’ amplitude-dependent stiffness and energy dissipation. The model is calibrated and validated against experimental tests conducted on dampers equal to the ones installed on the hangers of the Hålogaland long-span suspension bridge. Unlike impedance-based black-box models, the proposed framework provides a physically consistent representation that can be directly embedded into system-level simulations of hanger-damper dynamics. The present framework can accurately reconstruct both the overall transmitted force and the internal dynamics, in close agreement with the measured responses across varying amplitudes and frequencies. In comparison to existing formulations developed for overhead line dampers, it requires no additional parameters but more effectively captures the amplitude-dependent variation of the damper’s dynamic behaviour, providing improved accuracy in representing its nonlinear characteristics.