Making the eye blink—modelling the operation of the Gateshead Millennium Bridge

Abstract

This paper considers the system dynamics associated with a hydraulic system moving a large flexible structure, namely the Gateshead Millennium Bridge. The hydraulic components possess a range of non-linear characteristics, which become coupled to the bridge structural dynamics. The bridge structure is lightly damped and may be represented by a linear model, provided that the amplitudes of vibrational modes are small enough to maintain positive cable tensions. The limiting amplitudes were known at the design stage and the hydraulic circuit had to ensure that these were not exceeded during operation, which may include various conditions of wind loading, emergency stops and variability of components. System design was achieved through an extensive iterative process of simulation that included all operational procedures to eliminate problematic circuits that would have caused instability or excessive bridge oscillations. The actual bridge and coupled hydraulic circuits underwent a series of commissioning trials and no undue problems were experienced. This indicated that the simulation procedures developed greatly reduced the risks associated with a unique structure actuated by a bespoke hydraulic circuit.

Keywords

hydraulic design structural dynamics dynamic stability precision control

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