* Corresponding author. Journal of Wind Engineering and Industrial Aerodynamics 77&78 (1998) 245 — 257 Vibration control of tapered buildings using TLCD T. Balendra*, C.M. Wang, G. Rakesh Centre for Wind-Resistant Structures, Department of Civil Engineering, National University of Singapore, 10 Kent Ridge Crescent, Singapore 119260, Singapore Abstract This paper examines the effectiveness of the Tuned Liquid Column Damper (TLCD) when equipped on linearly tapered structures that cover uniform buildings to obtain pyramid- shaped buildings. Both shear and flexural behaviour are considered by modelling the buildings as shear-flexure beams. The pyramid-shaped Transamerica building which has closely spaced natural frequencies is studied to illustrate the importance of using additional dampers. Also the optimum positioning of these additional dampers is considered.  1998 Elsevier Science Ltd. All rights reserved. Keywords: Tuned liquid column dampers; Vibration control; Buildings; Wind induced vibration 1. Introduction The scarcity of land in many developed countries has resulted in design and construction of very tall and slender buildings. These buildings which are generally lightweight and lightly damped undergo significant fluctuating motions, due to wind and earthquake loadings, which may become unacceptable from the viewpoint of serviceability and safety. As such, the suppression of these vibrations has become an important design consideration in recent years. Many active and passive control devices such as active mass dampers, active tendons, tuned liquid dampers, impact dampers and tuned liquid column dampers (TLCD) have been proposed to mitigate these excessive vibrations. The TLCD, first proposed by Sakai et al. [1], is basically a U-tube container with an orifice opening in the middle. The TLCD dissipates the structural vibrational energy by the combined action that involves the movement of the liquid mass in the 0167-6105/98/$ — see front matter  1998 Elsevier Science Ltd. All rights reserved. PII: S 0 1 6 7 - 6 1 0 5 ( 9 8 ) 0 0 1 4 7 - 0