Bridge vibrations effectively damped by means of tuned liquid column gas dampers

Ziegler, F. and Kazemi Amiri, A. (2013) Bridge vibrations effectively damped by means of tuned liquid column gas dampers. Asian Journal of Civil Engineering, 14 (1). pp. 1-16. ISSN 2522-011X

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    Abstract

    Sealed tuned liquid column gas dampers, i.e. with a gas spring effect taken into account, TLCGD, are ideally suited to increase the effective structural damping of bridges when vibrating in the critical low frequency band. The evident features of this type of absorbers are no moving mechanical parts, cheap and easy implementation, low maintenance costs and simple modification of the natural frequency, and even of the damping properties (by means of built-in orifice plates). Modal tuning in the design stage by means of the analogy to the classical mechanical damper of the spring-mass-dashpot type, TMD, is subsequently followed by fine-tuning in state space, rendering the absorber parameter (frequency and damping) optimal and, when designing smaller units in parallel action, yields the control even more robust. The equilibrium gas-pressure is the main control parameter to optimize the absorber frequency when the volume of the individual gas vessel above the liquid-gas interface is properly selected. U- or V-shaped TLCGD with horizontal extension maximized, are proposed to reduce dominating horizontal vibrations of long-span bridges (including pedestrian bridges) and, as worked out in detail, in the case of the cantilever method of bridge construction, to increase the allowable maximum length of the cantilever, despite of wind-gusts. An alternative design, VTLCGD provides the control force vertically, and thus counteracts dominating vertical, traffic-induced vibrations. Sealing of the piping system in that case is a necessary condition since an equilibrium gas-pressure difference is essential for the vertical action of the displaced fluid. The horizontal length of this absorber is kept to a minimum. Illustrative examples are described to convincingly approve the un-revealed action of the liquid absorber.