Taipei 101

Statistics

In-Depth Analysis by Michael W. Su

At the moment of this writing, the records for the highest structural top, highest roof, and highest occupied floor are still held by the Taipei 101 Tower in Taipei, the capital city of Taiwan, R. O. C. Respectively, these heights are: 509m at the top of the structural spire, 449m at the highest roof, and 439m at the highest floor – the one hundred and first. Just as notably, these records were achieved despite the tower’s location in one of the most active seismic and typhoon regions in the world. In order to reach these heights and still meet the rigidity and flexibility demands of the extreme lateral loads, e. g. – earthquakes above magnitude seven and winds above 60m per second (over 200km per hour), the architect, C. Y. Lee & Partners, and the structural engineers Thornton-Tomasetti Inc. and Evergreen Consulting designed the steel and reinforced-concrete tower with features that readily invoke superlatives.

      The building rests on a massive 5m thick concrete mat foundation laid over a veritable forest of 380 1.5m diameter concrete piles which are embedded with added high-strength concrete over 30m into the bedrock. From this foundation, 36 extra-high strength steel and concrete columns formed from just about the strongest steel and concrete available begin their ascent. Of these, twelve are corner and bracing columns ending at floor 26, sixteen are full height columns that form the core, and eight are full height, 3m x 2.4m “mega-columns” distributed around the perimeter. All are steel box columns assembled from 413MPa (60ksi) yield-strength steel plates up to 8cm thick and then formed into composite columns by either partially or fully filling their volumes with 70MPa (10,000psi) concrete up to the 62^nd floor. (Curing tests indicated that this concrete strength actually reached 80MPa [12,000psi].)

      To counter lateral forces, shear walls are formed by casting concrete within the spaces between the core composite columns in a 4 bay x 4 bay configuration from the foundation to the eighth floor. Above the eighth floor, core columns are reinforced with moment-jointed beams at each floor and then braced through to the top floor. Additionally, one- and two-story high outrigger steel trusses tie the core columns to the perimeter mega-columns at every eighth floor. The curtain wall system of glass panels installed into inclined moment-resisting lattices contributes to overall lateral rigidity by tying back to the mega-columns with one-story high trusses – also at every eighth floor. This facade system also accommodates lateral displacements such as those caused by seismic activity of up to 95mm without damage. Finally, deflections resulting from extreme wind loads are minimized by the installation of three separate tuned-mass dampers: a primary, low-frequency 635,000kg damping sphere almost 6m in diameter formed from 41 layers of 12cm thick steel is suspended between the 92^nd and the 88^th floor to counter overall tower sway, while two smaller, higher-frequency dampers 7 tons in weight are installed inside the 20m tall mast to counter mast vibrations. The engineers noted that this final structure is expected to survive once-in-2,500 year seismic events, i. e. – events which produce accelerations up to 0.5g at ground level. It is the very implementation of these innovations that allows the Taipei 101 Tower to achieve lateral resistances comparable to towers with more traditional structural cores of monolithic reinforced concrete walls, but without incurring the associated penalties in weight, assembly time, and most critically, free floor space.

      Besides its state of the art building systems, the Taipei 101 Tower is also equipped with 48 of the world’s most advanced elevators. The elevators are installed in a novel staggered-transfer configuration with two sky lobbies and four transfer floors. Most of these have aerodynamically shaped, double-decked pressurized cabins and travel at very high speeds. But, the two elevators traveling between the lobby and the 89^st floor observation deck can claim to be the fastest elevators in the world. Custom designed for the tower, these record-setting elevators took over one year to build and four years to install. Amazingly, they reach speeds of over 60km per hour and rise from ground level to the observation deck in just under 40 seconds.

      Undoubtedly, these structural and service innovations will ensure that the Taipei 101 Tower continues to be recognized for its accomplishments even after it cedes the various height crowns to newer buildings in Dubai and China over the next few years.