Reduction of the cross-wind response of a tall building using tuned liquid dampers for economic design of the structure

Rasuna Tower is an office and hotel development in Jakarta, Indonesia with 63 above-ground storeys and 4 basements. The floor plate is nominally 34m x 56m and the tower is approximately 280m tall. The lateral resistance is provided mainly by the core walls, with outrigger beams to the perimeter in the weak direction at L44. Wind tunnel testing has shown that the structure is subject to a strong cross-wind response (in its 1st mode - weak axis direction) if the building natural frequency is at the lower end of the predicted range, and that this dynamic wind response is more severe than earthquake. The relatively soft foundations will tend to reduce the building stiffness and consequently reduce the frequency. The extent of this effect is however difficult to predict. Similarly, the level of damping provided by raft of soft foundations is hard to predict. Several alternatives were considered for accommodating the dynamic cross wind response of the building: 1) Design the structure for the high forces. This is the most expensive option. 2) Modify the shape of the facade at the top half of the building. This potentially offered the largest reduction in structure cost but was not preferred by the Owner. 3) Introduce auxiliary damping to reduce the dynamic response. With an additional 2% auxiliary damping the 500 year building base moment was reduced by approximately 20%. The decision was made to provide additional damping, in the form a pair of tuned liquid column dampers. Each tuned liquid column damper has an embedded tuned liquid sloshing damper. This damper is important in controlling the response of the tower such that building's cross-wind response is similar in magnitude to the along-wind response. Building accelerations do not require mitigation and easily meet the various comfort criteria. The rotational velocities are slightly high and this is addressed with the same dampers.