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Serviceability of buildings has been emphasized due to an increase in the construction of high-rise buildings and resident requirements. The increasing height and span of structures are resulting in their increased vulnerability to environmental forces such as winds, earthquakes and sea waves. Tuned Liquid Column Damper (TLCD) systems can be considered as a particular type of passive mass dampers. Even though several TLCD models have been proposed and many optimization algorithms have been developed, however, it is very low researches that have been conducted to evaluate the TLCD damping factor experimentally. A simple method to adjust the TLCD damping factor is by varying the orifice blocking ratio. In the research, 5 types of orifice blocking ratio are varied in the TLCD. They are without orifice, 2 hole orifice TLCD, 4 hole orifice TLCD, 6 hole orifice TLCD, and 8 hole orifice TLCD. The data obtained is in frequency response function showing magnitude of structure model’s natural frequency. Impact hammer is used as the excitation force. The result shows that the TLCD with orifice is better in damping vibration compared to the one without orifice. The smaller orifice blocking ratio the better TLCD damping the vibration. The 2 hole orifice TLCD fails to dampen the vibration since the orifice blocking ratio is too small and TLCD becomes too stiff. The optimum condition of a U-Shaped TLCD orifice blocking ratio is 29.23% which has 4 holes of 18 mm orifice diameter. Keywords: TLCD, orifice, damping factor, blocking ratio.

Tuned liquid column damper (TLCD) is a simple technique used to increase the structure resistance to the external load. This type of damper can effectively decrease the structure response when the TLCD parameters such as the natural frequency and damping factor are well selected. Even though several TLCD models have been proposed and many algorithms to optimize the TLCD parameters have been developed. However, it is very little research has been conducted to evaluate the TLCD damping factor experimentally. A simple method for adjusting the TLCD damping factor empirically is by varying the orifice blocking ratio. In this research, 5 types of blocking ratio were trialled in the TLCD. They were without orifice and with 2, 4, 6 and 8 18 mm diameter orifices. The TLCD is positioned at the second floor of a Two-DOF shear structure. A frequency response function showing the ratio between the response magnitude and the excitation force on the structure in the frequency domain was recorded for each trial. The results show that the TLCDs with orifices damped vibrations more effectively than the one without orifice. The larger the blocking ratio, the larger the TLCD damping factor. Two 18 mm orifices were insufficient to damp the vibration as the blocking ratio is too large and TLCD is less responsive to the vibrations. The optimum condition of a U-Shaped TLCD blocking ratio was found to be 70.77% which corresponded to 4 holes of 18 mm orifice diameter. This type of TLCD dampened up to 80.04% of the vibration magnitude.