By Rob GossJan 20
As the world was harshly reminded by the 9.0-magnitude Great East Japan earthquake and resulting tsunami in 2011, Japan is beset by seismic activity. The country experiences an earthquake every five minutes, 2,000 of which each year are large enough to be felt. Put into a global context, approximately 20% of the...
As the world was harshly reminded by the 9.0-magnitude Great East Japan earthquake and resulting tsunami in 2011, Japan is beset by seismic activity. The country experiences an earthquake every five minutes, 2,000 of which each year are large enough to be felt. Put into a global context, approximately 20% of the world’s 6.0-magnitude quakes or greater hit the country.
In cities like Tokyo–where the greater urban area has a population of some 35 million–it’s a case of when, not if the next major earthquake will come. For architects and engineers that means a constant quest to find new solutions to protect buildings and those in them from the inevitable.
High Rise Buildings, Concrete-filled Tubes and Sticky Walls
In particular, in a country that is increasingly growing upwards, architects and engineers are continually looking for better ways to earthquake-proof high-rise structures. When Mori Building Co. (the company behind many of Tokyo’s most prominent office buildings and tower complexes) built the $2.5bn Roppongi Hills “city within a city” complex, they built it to be what they termed “a city to escape to, rather than flee from,” utilizing a variety of seismic isolation and damping technologies.
In the complex’s 238-meter Mori Tower they installed 356 oil dampers that work to absorb the shaking of the building with the resistance force generated by the movement of the oil, the flow of which is controlled by movement sensors triggered by seismic activity.
Throughout the complex, Mori also employed concrete-filled tube (CFT) columns for the building framework, where the inside of the steel pipes is filled with high-strength concrete to give increased resistance strength and deformation capacity. In the high-rise Roppongi Hills residences, another technology used was “viscous damping wall” in the flooring. With that, a highly sticky substance is injected into the inside of multiple box-shaped steel plates that are installed in the central section of each floor and which then generate a resistance force during an earthquake.
Energy Dissipative Braces and Carbon Fibres
In an array of industries Japan has built a reputation for novel solutions and earthquake-resistant building design is no exception. In November, architect Kengo Kuma (the man chosen to design the 2020 Olympic and Paralympic Games stadium) and fabric manufacturer Komatsu Seiren combined to create the three-floor Fa-bo office in Ishikawa Prefecture, using large carbon fibers set up outside the building as a seismic support.
The striking result, with the fibers seemingly wrapping the minimalist concrete structure inside like a spider’s web around a fly, is the first time carbon fibers have been used as an earthquake-resistant material.
The fibers, called CABKOMA Strand Rods, are a thermoplastic carbon fiber composite using carbon fiber as the interlining and employing an outer layer covered with synthetic fiber and inorganic fiber. It is then finished by impregnation with thermoplastic resin, with the overall result being high tensile strength at an extremely light weight. In a video interview explaining his attraction to carbon fiber, Kuma says that “despite being stronger than metal, it’s very light and thin. What’s more, it’s not visually obvious, which makes for transparent quake resistance…and allows a freedom of space and light.”
Structural Design for The Home, Convincing Clients
Equally experimental has been the Japanese company AirDanshin, which has been working on housing that can “levitate” during an earthquake. How effective this could be is still up for discussion in its present state of development, but the theory is that the house would sit on a deflated air bag. When the house’s sensors feel a tremor, they would immediately switch on a compressor that pumps air into the airbag which would lift the house several centimeters off the ground for the duration of the tremor.
However, unlike high-rise construction, with technology for housing lax regulation seems to be holding back structural design. “By law, houses under 200 square-meters and less than three stories don’t require detailed structural design or building certification, so it’s difficult to convince clients to pay for structural design,” Tamotsu Teshima of Tokyo-based T.Teshima Architects and Associates, who works in collaboration with structural engineer Noriaki Yamada, told ArchiExpo.
“Additionally, even if there is the possibility of liquefaction, land subsidence or landslides, and even if engineers insist on the importance of subsurface investigation and foundation, budget restrictions often prevent sufficient investigation. With the Great East Japan Earthquake many houses were damaged by liquefaction and landslides, which should make us re-recognize the importance of ground and building foundation,” he says.
“Ground choice isn’t the only non-structural element that needs more attention,” Makiko Tsukada of Makiko Tsukada Architects told ArchiExpo. Tsukada, who in projects like her 2015 Sukima Atelier (a three-story combined home, gallery and workspace) is known for using large sheets of glass as part of the interior design.
“Because of the large glass we use, we are always careful to employ anti-shattering films, and with something like a ceiling [or curtain wall] it is very important to take measures to prevent collapse,” Tsukada says. The latter can be as simple as using additional nails and glue to secure a ceiling, or simply avoiding suspended ceilings and designing a house with the concrete and structural supports showing.
Sukima Atelier by Makiko Tsukada Architects:
What the 2011 earthquake taught Japan was that its ever-developing structural technology was most definitely averting disaster and saving lives, but with most building damage non-structural, and this still impairing building function, Japan’s next step needs to be to make earthquake-resistance more holistic.