Structural Design
The technology behind 634m
A huge tower of 634m,
How do you support it safely?
TOKYO SKYTREE is the world's only structure that combines cutting-edge technology with Japanese ingenuity.
We will explain in an easy-to-understand way the structural design ingenuity that made it possible to achieve that height and safety.
A breakdown of the structural design of TOKYO SKYTREE, section by section.
STRUCTURAL
DESIGN?
First, start with research into unknown areas
The height of TOKYO SKYTREE is approximately 634 meters.
In 2006, when the construction site for TOKYO SKYTREE was decided to be the Oshiage district of Sumida Ward, the tallest structure in Japan was the Tokyo Tower(designed by Nikken Sekkei), completed in 1958, at approximately 333 meters.
After approximately 50 years, they are attempting to reach nearly double the height, a feat never before accomplished, making it a "challenge into uncharted territory" utilizing cutting-edge technology.
To ensure safety, we began by researching this uncharted territory.
Knowing the wind at 600m above ground
To find out what kind of winds are blowing 600 meters above the ground, we launched a weather balloon called a radiosonde to investigate wind speed distribution and wind turbulence at high altitudes. In addition to regular ground surveys, we also conducted a rare survey method (microtremor array survey) to investigate the deep geological structure up to about 3 km underground, allowing us to more accurately simulate how this location would shake during an earthquake.
Through these detailed investigations, various design innovations and verifications, we have confirmed safety against earthquakes and strong winds, which are not anticipated in the design of ordinary high-rise buildings.
Like a big tree,
How to connect with the ground
The taller a building is, the greater the "pulling force" and "compressing force" exerted on its foundation by shaking during earthquakes and Strong winds.
In the case of a tall, slender structure like this Tower, particularly large forces are exerted.
This difficult problem needed to be solved through ground design.
Wall posts that look like the soles of spiked shoes
To counter this, the foundation piles are made wall-like with joints to increase frictional resistance. These joints are like the soles of spiked shoes. Furthermore, by connecting these wall piles and stretching them radially underground, the intention is to integrate them with the ground like tree roots.
Furthermore, the Steel framework of the Tower visible above ground is continuously connected to underground piles, directly transmitting forces. In other words, it could be said that it "stands like a giant tree that has sprouted from the earth."
Connect and integrate Steel framework frame design
The secret behind the high-strength steel materials that support the Tower
We use "high-strength steel pipes" as structural components, which are about twice as strong as standard Steel framework.
The steel pipes at the base of the Tower are enormous, measuring 2.3 meters in diameter and 10 centimeters thick.
The tower's structure is a "Truss structure," a structural framework in which main members, horizontal members, and diagonal members are joined together in a triangular shape. The members are joined using a method called "branch joints," which involves directly welding steel pipes together without the use of plates or other intermediaries. This method is both aesthetically simple and offers advantages in terms of corrosion resistance.
Overview of the Steel framework framed tower
| Kanae (tripod kettle) Truss | The structure is made up of four columns, horizontal members, and bracing members, which are placed at each vertex of a triangular plan. It serves as the main structure that resists horizontal loads. |
|---|---|
| Horizontally Connected Truss | The central tower is a column that connects the ring truss every two stories (25m). It acts as a transmission member for horizontal forces (in-plane) and as a buckling stiffener for the Kanae (tripod kettle) truss and outer perimeter columns. |
| Ring truss | Horizontal members placed every other story (12.5m) act as buckling stiffeners for the outer columns. |
A new mechanism to reduce building sway Central pillar vibration control system
After various attempts to create a safe and secure building against earthquakes and Strong winds, we have adopted a new vibration control system that structurally separates a reinforced concrete cylinder (Central pillar) in the center from the Steel framework framed tower on the outer perimeter, with the upper part of the central Central pillar functioning as a "weight."
The principle behind it is an application of a modern vibration control technology called a "mass addition mechanism," which can reduce the response shear force by about 40% during a major earthquake. On the other hand, Tradition Japanese pagodas, such as the "Five-story pagoda*", have never collapsed due to earthquakes, and it is speculated that the secret lies in the central pillar of the building, also known as the "Central pillar ."
With deep respect for this ancient wisdom, we named it " Central pillar Control," drawing an analogy to a Five-story pagoda .
- The Five-story pagoda is a unique type of wooden structure found only in Japan. Although there have been instances of collapse due to typhoons and fires, there are no records of it collapsing due to earthquakes, and it is said to be a building with excellent earthquake resistance. There are various theories as to the reason for its high earthquake resistance, but it is believed that the central pillar, known as the "Central pillar," plays a major role.
Mass addition mechanism
This vibration control system suppresses the overall shaking of a building by adding an additional mass (weight) that vibrates at a different timing than the main building during earthquakes, thereby canceling out the vibrations of the main building and the additional mass. While steel blocks or concrete blocks are typically used as the additional mass, there are also examples of using large pieces of equipment or heat storage tanks. This is the world's first example of using a Central pillar(Staircase) as the additional mass.
The Central pillar of TOKYO SKYTREE
In the context of TOKYO SKYTREE, this refers to the central cylindrical section (made of reinforced concrete, with an emergency Stairs inside). It was named "Central pillar) out of deep respect for the ancient wisdom surrounding Five-story pagoda .
Content provider
Nikken Sekkei Ltd. "TOKYO SKYTREE Design Project"
Special content from Nikken Sekkei, the company involved in the design of TOKYO SKYTREE.
You can view content that approaches TOKYO SKYTREE from a structural design perspective, including the structural technologies actually used and the voices of the designers who participated in the project.
