Taipei 101 Case Study: Mega Frame, Outriggers and the Damper (C Y Lee)

Taipei 101 is a 101-storey tower in Taipei by C.Y. Lee & Partners, completed in 2004 and the world's tallest building until 2010. For architecture students it shows how a tall building is held up against typhoons and earthquakes: eight super columns, outrigger trusses on the mechanical floors, piles driven into rock, and a 660-tonne steel ball near the top that calms the sway. Below: brief, site, concept, plan, structure, damper, construction, services, reception and lessons for India.

The brief and the client

The Taipei Financial Center Corporation built the tower as offices, a financial address and a landmark. Its corporate page sets Taipei 101 beside the Empire State Building and the Eiffel Tower and says Taipei needed "a wider stage". It credits construction management to Moh and Associates with Turner International, and construction to the KTRT group (Kumagai Gumi, Taiwan Kumagai, RSEA Engineering and Ta-Yo-Wei Construction); the CTBUH Skyscraper Center also lists Samsung C&T.

A Bloomberg report in the Taipei Times (July 2003) records that in 1999 the project was cancelled when aviation authorities ordered the height cut to 60 storeys, and resumed after flight paths were changed. It gives the cost as NT$58 billion (US$1.7 billion), a figure published before completion; we found no final audited cost and have not converted it to rupees.

Site and context: soft ground, a fault and typhoons

The tower stands in Xinyi, Taipei's planned business district, on difficult ground. Building Design + Construction (BD+C), in an account written during construction, says the piles pass through about 160 ft (49 m) of soft soil to reach rock. A STRUCTURE magazine review (January 2026) adds a high water table and an active fault nearby, and gives a design wind speed of 156 km/h for a 100-year return period. BD+C says the tower was designed for a 950-year earthquake and a 100-year windstorm.

Wind calls for a stiff building; earthquakes punish one that cannot bend without breaking. The structure below answers both. To set out a site study like this, see our field checklist for documenting a building.

Taipei 101 design concept: eight modules of eight floors

The form is a stack. Above a base section that tapers inward, eight modules of eight floors sit one on another, each flaring outward as it rises. The owner's design concept page (in Chinese) explains that eight sounds like the word for prosperity, so the designers took eight floors as one structural unit and stacked the units. It compares the shape to bamboo rising joint by joint and to a flower opening, and says the stepped form, with planting between, helps break up the wind that tall buildings send down to the street.

The Skyscraper Museum adds that coin shapes are fixed to the outside at the 26th floor (the round medallions in the photo) and that a feng shui master was consulted. Those are symbols; the eight-floor module also does structural work, as the next sections show.

Taipei 101 floor plan and zoning

A shopping mall fills the base, which the owner lists from B1 to the 6th floor. Offices fill the tower, and the observatory occupies levels 89, 91 and 101. CTBUH counts five basement levels.

A typical office floor is a square plate around a central core of lifts, stairs and services. Each corner steps in twice, a "double notch" that STRUCTURE gives as 2.5 m deep. Two super columns stand on each face, about 74 ft (22.5 m) apart according to BD+C. Because the faces slope, the plate changes size through each module. The architects' plans are not published online in full, so the diagram is our schematic of the published descriptions.

Taipei 101 structural system: mega frame and outriggers

The structure is composite, steel filled with concrete, in four parts:

• Super columns. Eight, two per face. STRUCTURE describes hollow steel boxes up to 3 m by 2.4 m at the base, of plates 50 to 80 mm thick, filled with concrete of about 69 MPa (10,000 psi) and rising to level 90. BD+C says the high-strength fill runs to level 62.
• A braced core. Sixteen steel box columns in four lines of four, braced between floors and encased in concrete up to the 8th floor (STRUCTURE).
• Outriggers and belt trusses. On the mechanical floors, deep trusses tie the core to the super columns and tie the perimeter together, so core and columns resist overturning as one. The owner's structure page places the outriggers on the mechanical floors; BD+C and STRUCTURE say every eight to ten floors.
• Sloping moment frames. Steel frames along each sloping face. BD+C says the beams have reduced sections that let them rotate slightly in an earthquake, and that pick-up trusses at each setback carry the sloping perimeter columns onto the super columns.

Below about level 26, BD+C describes extra concrete-filled columns on each face to resist uplift. The eight-floor module is where all this meets: every eighth floor is a mechanical floor, a truss floor and, the owner's building systems page adds, a floor with refuge rooms.

The corners and the wind

Sharp corners shed wind in alternating swirls that rock a tower across the wind. RWDI tested corner shapes in its wind tunnel; the Science Museum Group in London holds four model corners from those tests. STRUCTURE reports that the double notches cut crosswind response by as much as 40% compared with sharp corners. We did not find RWDI's own report, so treat that as the article's figure.

Taipei 101 foundation

The owner says 380 piles, each 1.5 m across, were driven about 80 m into the ground, the deepest 30 m into bedrock. BD+C, during construction, gives 550 piles about 260 ft (79 m) long, 80 ft (24 m) into rock, each load-tested. We could not reconcile the counts from published sources.

Taipei 101 tuned mass damper: how the giant ball works

A tall building can be safe and still sway enough to make people feel unwell. BD+C reports that early wind tests showed vibrations 30 to 40% above recommended levels, and the damper was added for comfort. The owner's damper page says its "main purpose is to reduce swaying by strong winds". The figures, from the owner and the designer, Motioneering (winter 2024 newsletter):

• Mass: 660 tonnes. Thornton Tomasetti and BD+C say 730 tons; Guinness World Records gives 660 tonnes as 728 US tons, so it is the same mass in short tons.
• Size: about 5.5 m across, 41 steel plates each 12.5 cm thick, welded into one sphere.
• Hanging: from cables anchored at level 92. Motioneering puts the mass on level 87; Guinness says between 87 and 92. The owner gives 92 cables, 8.9 cm thick and 42 m long; BD+C says eight cables.
• Damping: eight hydraulic viscous dampers under the ball, and a bumper ring that limits the swing to 150 cm (owner). BD+C adds two dampers of about five tons each in the pinnacle.

How it works: the ball is a pendulum tuned to the tower's own sway. When wind pushes the top one way, the ball lags, swings out of step and works against the movement, and the hydraulic dampers turn that motion into heat, so the sway dies down sooner. In an earthquake, STRUCTURE notes, the dampers and bumpers also stop the ball swinging too far.

Taiwan News (August 2019), citing Taipei 101, gives the largest movement as about 100 cm during Typhoon Soudelor on 8 August 2015, and the largest earthquake movements as 20 cm and 15 cm, both in 2019; Guinness also gives 1 m for Soudelor. The claim that the damper cuts sway by up to 40% is the owner's figure; we found no published measurement behind it. C.P. Wang of C.Y. Lee & Partners called the damper "the heart of the building" (BD+C).

Materials and construction

The skin is a glass curtain wall. Permasteelisa says it built more than 125,000 m² of pressure-equalised, unitised facade designed for seismic and typhoon loads, in aluminium, glass, stainless steel and stone; the Taipei Times (2009) calls the glass double-pane low-emissivity.

On 31 March 2002 a magnitude 6.8 earthquake shook two tower cranes loose from the 56th floor, and the Taipei Times reported five workers killed. BD+C says work resumed on 28 June 2002 with strengthened cranes, and records a roof fire in January 2003. The last steel beam went up on 1 July 2003 and the 400-ton pinnacle was jacked into place that October. C.Y. Lee, quoted by BD+C from a PBS documentary, said: "We had so many problems, I think it's a miracle that we can get it done in this time and in this place."

Light, climate and services

The owner describes an ice-storage system that makes ice at night on off-peak power to cool the building by day, eight diesel generators able to run for 46 hours, and outdoor refuge platforms on the mechanical floors above the 34th. The observatory lifts climb at up to 1,010 m a minute, 37 seconds from the 5th to the 89th floor. After a NT$60 million retrofit announced in 2009, forecast to save about NT$20 million a year (Taipei Times), the owner reports LEED certification in 2011, 2016 and 2021, including LEED v4 Platinum in July 2016.

Reception: records, a quake theory and a mascot

Taipei 101 was the world's tallest from 2004 to 2010 (Thornton Tomasetti). When CTBUH named it tallest in October 2004, its chairman Ron Klemencic said it surpassed the Petronas Towers by 56 m (Taipei Times). CTBUH now ranks it 11th in the world.

In 2005 Lin Cheng-horng, a geologist at National Taiwan Normal University, argued in Geophysical Research Letters that the tower's weight may have reopened an old fault after two felt earthquakes occurred beneath it. The Taipei Times carried the doubts too: John Vidale of UCLA said a building's stress "probably won't reach down" to where the quakes occurred, and Zygmunt Lubkowski of Arup said it was hard to tell whether the extra quakes were "just noise in the signal". Treat it as a disputed hypothesis.

The damper itself became an attraction. Motioneering notes that it inspired a mascot, Damper Baby, and the owner shows it to observatory visitors.

What designers in India can take from it

This is our reading, not a claim from the sources.

1. Let one module organise form, structure and services. Here the eight-floor unit sets the facade steps, the truss floors, the plant and the refuge rooms. On a 20 to 40 storey Indian tower, decide early which floors carry trusses, plant and refuge space, and stack them.
2. Treat comfort as a design load. Strength alone does not stop people feeling a tower move. In cyclone-exposed cities such as Mumbai or Chennai, get wind advice on the shape before the facade is fixed; corner shaping costs less than a damper added later.
3. Know the ground first. The scale differs for a house, but the order is the same: soil report, then structure. See our guide to foundations on black cotton soil.
4. Separate claims from measurements. "Up to 40%" and "NT$20 million a year" are a claim and a forecast. In a thesis or jury, say which figures were measured and by whom.

For a tall-building thesis, our B.Arch thesis topics by typology lists commercial and mixed-use briefs. Our 30 St Mary Axe case study, another tower whose structure shapes its form, is in the same series.

Visiting Taipei 101

The mall and observatory are open to the public; the offices are not. The official site lists observatory hours of 10:00 to 21:00 daily, with the ticket counter on the 1st floor of the office tower, and says visitors to the observation deck can see the damper. Check the site for tickets and closures before you go.

Looking for an architect who thinks about structure and form together? Find an architect on MOA.

FAQ

When was Taipei 101 built?

Ground was broken in January 1998 by the Skyscraper Museum's account (CTBUH gives a 1999 start). The last steel beam went up on 1 July 2003, the pinnacle in October 2003, and the tower was completed on 31 December 2004.

Who designed Taipei 101?

C.Y. Lee & Partners, the Taipei practice of architect C.Y. Lee, designed it. The structural engineers were Evergreen Consulting Engineering and Thornton Tomasetti, and Motioneering designed the damper.

How tall is Taipei 101 and how many floors does it have?

It is 508 m to the architectural top (CTBUH), given as 1,667 ft or 1,671 ft depending on the source. It has 101 floors above ground and 5 below; the highest occupied floor is at 438 m.

How heavy is the Taipei 101 damper ball?

660 metric tonnes, about 5.5 m across, made of 41 steel plates. American sources often say 730 tons, which is the same weight in US short tons.

Is Taipei 101 earthquake proof?

No building is earthquake proof. Taipei 101 was designed for strong earthquakes and typhoons with super columns, outrigger trusses, ductile moment frames and deep piles; BD+C says the design earthquake has a 950-year return period. The damper mainly improves comfort in wind.

Sources

• TAIPEI 101: Building structure. Structural designer and peer reviewer, piles, outrigger trusses, giant columns (accessed 4 Nov 2026)
• TAIPEI 101: 101 design concept. The number eight, the eight-floor unit, bamboo and flower imagery, street-level wind (accessed 4 Nov 2026)
• TAIPEI 101: Observatory features: wind damping ball. Damper size, plates, mass, cables, hydraulic dampers, bumper ring, maximum swing (accessed 4 Nov 2026)
• TAIPEI 101: Building systems and energy efficiency. LEED and WELL certifications, ice storage, power, generators, refuge floors, lifts (accessed 4 Nov 2026)
• TAIPEI 101: About us. Corporate aim, architect, construction managers and contractors (accessed 4 Nov 2026)
• TAIPEI 101: Home page. Observatory and mall floors, hours (accessed 4 Nov 2026)
• CTBUH Skyscraper Center: Taipei 101. Heights, floors, area, lifts, dates, project team, ranking (accessed 4 Nov 2026)
• Thornton Tomasetti: Taipei 101. Its role, height in feet, damper weight, years as tallest (accessed 4 Nov 2026)
• Jannat Ara Jabin and Krishna P. Ghimire, STRUCTURE magazine: Dynamic Loading Solutions in Taipei 101, 2 January 2026. Super columns, core, outriggers and belt trusses, design wind, corner notches, how the damper works (accessed 4 Nov 2026)
• Building Design + Construction: Over the Top (written during construction; the online page is dated 11 August 2010). Super column size and spacing, base columns, piles, design return periods, damper and pinnacle dampers, construction setbacks, quotes from Dennis Poon, C.P. Wang and C.Y. Lee (accessed 4 Nov 2026)
• Motioneering: Resonance newsletter, winter 2024. Damper location, size, mass, hydraulic cylinders, Damper Baby (accessed 4 Nov 2026)
• Guinness World Records: Largest tuned mass damper. Mass in tonnes and US tons, maximum extension, Soudelor swing, completion date (accessed 4 Nov 2026)
• Keoni Everington, Taiwan News: Video shows 2nd-largest movement of Taipei 101 damper in history during 6.0 quake, 8 August 2019. Recorded damper movements, the 40% claim (accessed 4 Nov 2026)
• Science Museum Group: Four detachable model corners relating to the wind tunnel tests of Taipei 101. RWDI's corner models (accessed 4 Nov 2026)
• Permasteelisa Group: Taipei 101. Curtain wall area, system and materials, podium (accessed 4 Nov 2026)
• The Skyscraper Museum: Taipei 101. Groundbreaking date, topping out, coins at the 26th floor, feng shui (accessed 4 Nov 2026)
• Bloomberg in the Taipei Times: Taipei 101 'a monument': Chen, 2 July 2003. Cost, last steel beam, 1999 height cut, developers (accessed 4 Nov 2026)
• Sandy Huang, Taipei Times: Probe into quake damage starts, 2 April 2002. Crane collapse and deaths, fault concerns (accessed 4 Nov 2026)
• Joyce Huang and Huang Tai-lin, Taipei Times: Taipei 101 earns highest compliment, 9 October 2004. CTBUH recognition, roof and occupied heights (accessed 4 Nov 2026)
• Taipei Times: TFCC to invest NT$60m in 'greening' Taipei 101, 4 November 2009. Green retrofit cost and forecast savings, glazing (accessed 4 Nov 2026)
• Taipei Times (from The Guardian): Taipei 101 faulted for earthquakes, 3 December 2005. Lin Cheng-horng's study and the replies from John Vidale and Zygmunt Lubkowski (accessed 4 Nov 2026)