Seismic isolation systems help mitigate earthquake damage

Seismic isolation is an excellent technology to help make structures more resistant to earthquakes by installing equipment to isolate a building from the ground and keep tremors from reaching the building. Seismic isolation systems reduce shaking by placing rubber, lead or other substances between structures and the ground, using them as a cushion to absorb tremors.

Buildings equipped with seismic isolation systems suffered minimal damage, even in the Tohoku region, during the Great East Japan Earthquake in March 2011.

One such building belongs to Starts Construction and Asset Management Co. (Starts CAM) in Sendai.

Starts CAM, a division of the Starts Group real estate and consulting conglomerate, completed construction of the eight-story residential building in March 2001. Its quake resistance was proven in the March 2011 quake.

The building sustained no damage and residents reported that not even a wine glass was broken.

“The landlord was an architect, so he was well aware of the benefit of seismic isolation systems,” said Shingo Chisaka, an executive officer in charge of structure design at Starts CAM. “Back then, Miyagi experienced a large earthquake about every 30 years.”

Since March 2011, building owners are increasingly aware of the necessity of quake resistance and the number of buildings with seismic isolation systems has steadily increased.

Starts CAM has received orders to construct 351 structures featuring seismic isolation systems in the 16 years through February that it has been building such structures. The company has received between 20 and 40 new orders every year since fiscal 2005, except for 2011 when it saw 49 new orders.

One drawback of seismic isolation systems is the high cost associated with them. Because of this, public buildings that are used by many people, such as schools, hospitals and government offices are typically fitted with the latest in seismic isolation technology.

However, Starts CAM is trying to lower the cost to make the technology affordable for ordinary residential buildings. For example, takayuka (high floor) seismic isolation methods are cheaper because they are installed at a higher level than regular seismic isolation systems, simplifying construction by reducing digging and foundation-laying work. The takayuka methods also enhace safety.

The company has also been able to gather detailed data after the March 2011 quake, thanks to its business portfolio covering everything from design, construction and operation of buildings.

For example, Starts CAM has seismometers in two buildings that are only 350 meters apart in Tokyo’s Edogawa Ward. One is a five-story building fitted with a seismic isolation system, while the nearby eight-story building has no such system.

The degree of shaking recorded at the building with seismic isolation system on March 11, 2011, was lower than that at the building without the system, according to Starts CAM’s data (see diagram at bottom left).

“These are very valuable data. We can check that the results are in line with the tremor-reducing effect we planned for when we designed the building,” said Tsutomu Nakanishi, who also oversees seismic isolation structure design at Starts CAM.

The company also installs seismic isolation systems in existing structures without requiring them to suspend operations. For example, it retrofit Honmyoin Temple in Tokyo’s Ota Ward with a seismic isolation system. This resulted in the temple seeing very little damage in the March 2011 quake.

Quake experience vehicle

Starts CAM is trying to raise awareness of the importance of seismic isolation and, to that end, it has been allowing people to experience a quake, both with and without seismic isolation, in a specially designed vehicle since 2006.

“We want as many people as possible to get on a quake experience vehicle and have firsthand experience of the severity of earthquakes and the safety of seismic isolation systems,” Chisaka said.

With the vehicle, people can experience eight different levels of shaking, including the levels of the Great East Japan Earthquake, the 1995 Great Hanshin Earthquake, the 2004 Niigata-Chuetsu Earthquake, the 1923 Great Kanto Earthquake and the 2008 Sichuan Earthquake.

People can also experience the difference in shaking with and without a seismic isolation system.

The vehicles are sent out about 20 times a month to various events such as university architecture classes, corporate disaster drills and conferences on disaster risk reduction. About 12,000 to 13,000 people experience quakes in Starts CAM’s vehicles each year.

Starts CAM tries to raise awareness of seismic isolation systems among not only residents of buildings with the systems, but also with the construction industry, people in charge of disaster risk reduction at companies and governmental organizations and others.

Further measures

Even if seismic isolation systems keeps buildings intact, suspension of lifelines such as water, gas and electricity will make it difficult to live day to day. Condominiums jointly developed by Starts CAM and energy supplier Iwatani Corp. focus on life continuity after disaster.

The condominiums are equipped with seismic isolation systems, as well as emergency wells in the event of municipal water supply disruptions. They also have propane gas tanks to use for kitchen, meaning gas supplies will not be suspended in the event of a disaster. Also, the gas can be used for power generation via a “counter-disaster energy system.” The condominiums are equipped to allow for the required minimum standard of living in the event of disasters.

“Starts CAM has a strong commitment to contribute to society through designing seismic isolation buildings and activities to promote such buildings, as well as to create buildings and communities with new disaster-risk-reduction technologies, including seismic isolation, by making full use of its technology, network and ideas,” Nakanishi said.

Overseas network

Starts CAM is part of the Starts Group conglomerate, which engages in everything from real estate, hotel operation and nursing services to financial services. It has 34 branches and subsidiaries in 22 countries. Its overseas operations are mainly real estate services for Japanese companies that are expanding offshore. It also operates hotels and golf resorts outside Japan.

It also plans to open a rental factory in the Philippines and build and operate hotels and serviced apartments in Phnom Penh, Cambodia.

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