Tuned Liquid Column Damper

A tuned liquid column damper (TLCD) is in many ways similar to a TMD that uses a heavy concrete block or steel as the tuned mass. The difference is that the mass is now water or some other liquid. The damper is essentially a tank in the shape of a U. It has two vertical columns connected by a horizontal passage and filled up to a certain level with water or other liquid. Within the horizontal passage, screens or a partially closed sluice gate are installed to obstruct flow of water, thus dissipating energy due to motion of water. The TLCD is mounted near the top of a building, and when the building moves, the inertia of the water causes the water to oscillate into and out of the columns, travelling in the passage between them. The columns of water have their own natural period of oscillation which is determined purely by the geometry of the tank. If this natural period is close to that of the building's period then the water motions become substantial. Thus the building's kinetic energy is transferred to the water. However, as the water moves past the screens or partially open sluice gate in the horizontal portion of the tank, the drag of these obstacles to the flow dissipates the energy of the motion. The end result is added damping to reduce building ocillations.

8.2.4.1. Wall Center, Vancouver, British Columbia

Shown in Fig. 8.30e is the plan for the mechanical penthouse of a building called Wall Center, a 48-story residential tower in Vancouver, British Columbia. From wind-tunnel tests, predicted 10-year accelerations were in the range of 40-milli-g, depending on the structural systems considered in the preliminary design. To minimize occupants' perception of motion due to wind excitations, a limit of 15 milli-g was chosen as the design criterion for a 10-year acceleration. A damper using water serves a dual purpose by also providing a large supply of water high up in the tower for fire suppression. Initially, a sloshing water damper was considered but the TLCD was found preferable due to its greater efficiency in using the available water mass. The design turned out to be a remarkably economical solution considering the saved cost of having to install a high-capacity water pump and emergency generator in the base of the building as initially required by fire officials. The total mass required was on the order of 600 tons which corresponds to a large volume of water. However, sufficient space was available. Also a helpful factor was that the motions of the tower were primarily in one direction only. Therefore only motions in one direction needed to be damped, which simplified the design. Figure 8.30f illustrates the TLCD design consisting of two identical U-shaped concrete tanks. Since the building was concrete, it was relatively easy to incorporate the tanks into the design and to construct them as a simple addition to the main structure. The structural design is by Glotman Simpson Engineers, Vancouver, British Columbia, Canada. The

-TLCD tanks

Figure 8.30e. Mechanical penthouse cross section of the Wall Center, a 48-story building in Vancouver, British Columbia. Two specially shaped tanks containing 50,000 gallons of water provide the mass for the building's TLCD. Structural engineering by Glotman Simpson Consulting Engineers, Vancouver, British Columbia, Canada; TLCD by Rowan, Williams, Davies, & Irwin, Inc., and Motion Engineering, Inc., Guelph, Ontario, Canada.

design of the TCLD is by Rowan, Williams, Davis, and Irwin, Inc., Guelph, Ontario, Canada.

8.2.4.2. Highcliff Apartment Building, Hong Kong

Another example of a tall building that uses TLMD to control accelerations and provide enhanced structural performance during typhoon conditions, is the 73-story Highcliff apartment building in Hong Kong, one of the windiest places on earth. The building soars to a height of 705 ft (215 m) with an astonishing slenderness ratio of 20:1. A unique

Figure 8.30f. TLCD for Wall Center, Vancouver, British Columbia. The motions of the tower were primarily in one direction only. Therefore only one direction needed to be damped. Two TLCDs extend nearly the full width of the tower. Within each tank is a long horizontal chamber at the bottom and two columns of water at each end. The dampers work by allowing the water to move back and forth along the bottom chamber of the tank and up into the columns of water.

Removable sections. Dimensions tied after building frequency is known. Both sides.

Figure 8.30f. TLCD for Wall Center, Vancouver, British Columbia. The motions of the tower were primarily in one direction only. Therefore only one direction needed to be damped. Two TLCDs extend nearly the full width of the tower. Within each tank is a long horizontal chamber at the bottom and two columns of water at each end. The dampers work by allowing the water to move back and forth along the bottom chamber of the tank and up into the columns of water.

Solid fill.

Dimensions tied after building frequency is known. Both sides.

Removable sections. Dimensions tied after building frequency is known. Both sides.

Figure 8.30g. Highcliff apartment building, Hong Kong.

structural system that incorporates all vertical elements as part of the lateral system, in combination with a series of tuned liquid mass dampers, ensures the safety and comfort of the buildings occupants.

Photographs of the building are shown in Fig. 8.30g. The structural engineering is by the Seattle firm of Magnusson Klemencie Associates.

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