Simple Pendulum Damper

The principle feature of the system shown in Fig. 8.30h is a mass block slung from cables with adjustable lengths. The mass typically represents approximately 1.5 to 2% of the building's generalized mass in the first mode of vibration. The mass is connected to hydraulic dampers that dissipate energy while reducing the swinging motions of the pendulum.

The adjustable frame is used as a tuning device to tailor the natural period of vibration of the pendulum. The frame can be moved up and down and clamped on the cables to allow the natural period of the pendulum to be adjusted. The mass is connected to an antiyaw device to prevent rotations about a vertical axis. Below the mass there is a bumper ring connected to hydraulic buffers to prevent travel beyond the hydraulic cylinder's stroke length.

Figure 8.30h. (1) Simple pendulum damper; (2) Hydraulic dampers attached to mass block. (Photograph courtesy of Dr. Peter Irwin of Rowan, Williams, Davis, & Irwin, Inc., Guelph, Ontario, Canada.) Taipei Financial Center

An example of a tuned mass pendulum damper (TMPD) architecturally expressed as a building feature is shown in Fig. 8.30i. At a height of 1667 feet (508 m), consisting of 101 stories, the building, called Taipei Financial Center, is poised to steal the crown from the twin Malaysian Petronas Towers as the tallest building in the world. A special space has

Figure 8.30i. Spherical damper, Taipei Financial Center, Taiwan. A 20-ft (6-m)-diameter steel ball assembled on site in layers of 5-in. (12-cm)-thick steel plate is suspended from level 92 by four sets of cables. Eight hydraulic pistons, each 6.5 ft (2 m) long, attached to the ball, dissipate dynamic energy as heat.

Figure 8.30j. (1) Simple pendulum damper; (2) nested pendulum damper.

been allocated for the TMPD near the top of the building and people will be able to walk around it and view it from a variety of angles. The TMPD, consisting of a 730-ton steel ball, will be brightly colored, and special lighting effects are planned. The architecture of the building is by C.Y. Lee and Partners, Taiwan; structural engineering is by Evergreen Consulting Engineering, Inc., Taipei, Taiwan, and Thornton-Tomasetti Engineers, New York; and the design of the TMPD is by Motioneering, Inc., a company in Ontario, Canada, that specializes in designing and supplying damping systems for dynamically sensitive structures.

8.2.6. Nested Pendulum Damper

In situations where the height available in a building is insufficient to allow installation of a simple pendulum system, a nested TMD may be designed as illustrated in Fig. 8.30j. The design shown is for a North American residential tower. The total vertical space occupied by the damper, which has a natural period of about 6 sec and a mass of 600 tons, is less than 25 ft (7.62 m), as compared to 30 ft (9.14 m) required for a simple pendulum. The design of the damper is by Rowan, Williams, Davis, and Irwin, Inc., Guelph, Ontario, Canada.

A nested pendulum damper is installed at the top of the 70-story, 971-ft-tall Landmark Tower, Yokohama, Japan. The damper requires only a one-story-high space, and is semi-actively controlled. Wind-induced lateral accelerations are expected to be reduced at least 60%. The damper design is by Mitsubishi Heavy Industries, Ltd., Tokyo, Japan.

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