With the development of high-strength materials and construction technology, modern buildings are becoming increasingly taller. Accordingly, the control of vibration induced by wind and earthquakes has become an important consideration in the design of high-rise buildings. There is a method of installing an additional vibration control device in a building as a method for improving the structural safety and serviceability of such a high-rise building. Among them, TLCD is a U-shaped liquid damper that controls vibration by using kinetic energy of water and damping force by orifices. However, since water itself does not have sufficient damping force, many studies have been carried out to increase the damping force by using orifices, valves or high viscosity liquids and so on. In this study, embossments on the wall of the damper was used to enhance the damping force and the tuned liquid column damper with embossments was named ETLCD.
Through this study, the dynamic characteristics of ETLCD was identified and the vibration control performance was examined by using the building scaled model experiment. Before the experiment, the analytical model of the conventional one was analyzed. The equation of motion and the natural frequency were derived and the equivalent linearization method was examined.
In the equation of motion, the damping coefficient includes the absolute value of the water surface velocity of the liquid column, so that the behavior of the damper is nonlinear and the natural frequency is dependent on the total length of the liquid column. In addition, the response of the structure and the damper has a mass linkage, and in particular, the horizontal mass of the liquid column is associated with the structure and acts as a control force.
In the characteristics experiment, the equivalent damping ratio was evaluated, and the theoretical and experimental natural frequency were compared. Experimental results show that the ETLCD exhibits non-linearity that the amplification factor is lowered as the excitation amplitude ratio increases, and the damping ratio increases by 1.6 times comparing with conventional one.
According to the result that the damping ratio was increased linearly with increasing the dimensionless amplitude ratio (D/L) in both ETLCD and conventional one, the equations to evaluate equivalent damping ratio, which depends on the dimensionless amplitude ratio was proposed. Also, since the experimental natural frequency is overestimated by at least 8% to 15% over the theoretical natural frequency in both of them, a correction coefficient for the length of liquid column is also proposed.
In the vibration control experiment using the building scaled model, free vibration and sine sweep forced vibration test were performed and the vibration control performance of the ETLCD was compared to the conventional one’s. For this purpose, the dampers were optimized for the building scaled model.
Experiment results show that the damping ratio of ETLCD was 2.7 times better than that of conventional one. The maximum acceleration response of the building was reduced by 43.1% after installing the conventional one, while it was reduced to 50.4% after ETLCD installation, which means that the control performance of the damper was about 1.2 times better than conventional one. Also, the damper showed stable control performance in all frequency bands, whereas conventional one showed a tendency to unnecessarily amplify the response in a specific frequency band.