Sealed liquid column damper (TLCD) are tuned in the low-frequency range of application (say below 5 Hz) with respect to a selected natural frequency of the main structure by means of a geometrical transformation in analogy to the classical tuned mass damper (TMD). To improve the performance in MDOF buildings even further, the influence of neighboring modes is taken into account by fine-tuning in state space, rendering the optimal parameters modified. Final adjustments are easily made in the course of in situ testing. The passive sealed TLCD making use of the gas-spring effect and, since turbulent damping of assigned strength is present, is perfectly suited to counteract steady-state vibrations. Reduction of transient vibration peaks, observed within the initial period of the strong motion phase of earthquakes, requires active control, realized by controlled pressure input into the gas volume. The TLCD is commonly sufficiently damped and the vertical component of the seismic excitation does not cause parametric resonance. A sufficient condition based on the cut-off damping must be checked. Computer simulations and small scale experimental testing under time-harmonic-, single seismogram- and random- forcing confirmed the excellent performance and robustness of the TLCD. Optimal solutions for benchmark MDOF structures with multiple TLCD are presented when excited either by wind gusts or by earthquakes. A base-isolated structure is considered with the effective damping supplied by a TLCD in the basement. Copyright (c) 2005 John Wiley & Sons. Ltd.
