TUNED LIQUID COLUMN DAMPER FOR VIBRATION CONTROL OF TALL STRUCTURES

Abstract

The performance of the Tuned Liquid Column Damper (TLCD) was studied when equipped on various structures. The study was divided into two phases. In the first phase of the study, a time domain analysis was carried out on a single degree of freedom systems. The governing equations of the TLCD contains a non-linear damping term. Most of the past studies have been carried out in the frequency domain using the linearised form of the TLCD equations. Up to now no complete time domain analysis to examine the effect of this nonlinearity has been carried out. Hence, the first phase of the study addresses this problem.

The performance of the TLCD can generally be said to be dependent on the structural, damper and excitation characteristic. Although there have been many studies made on determining the damper performance duo to variations in clamper and excitation characteristics, only limited study has been undertaken with regard to changes in structural characteristics. Hence in the second phase of the study, the performance of the TLCD is investigated when it is equipped on buildings with different structure forms such as frame, shear-wall and frame shear-wall structures and structure parameters such as height, stiffness, periods and damping ratios. Both uniform and non-uniform buildings are considered. Also the effect of damper positioning is examined. Unlike previous lumped mass formulations, a continuum formulation is adopted which gives a better overview of the general behavious of such structures.

These structures are modelled as shear-flexure cantilever beams. The along wind Harris spectrum has been used as the excitation force. The important response quantities studied would include the acceleration and displacement values. From the analysis, it was found that the effect of the non-linear damping term m the TLCD equation is negligible. The TLCD was found to be less effective with regard to both acceleration and displacement reduction when the damping ratio of the building is increased. The acceleration reduction ratio is independent of changes in the structural period whereas the displacement reduction ratio is smaller for stiffer structures. The performance of the TLCD was found to be very sensitive to its position for a purely flexural building and rather insensitive for a shear building. In cases where higher mode contributions are significant the use of more than a single damper proved to be very effective.