Unique anti-earthquake construction technology in Japan

Japan is the "meeting place" of many different tectonic plates such as the Pacific, Asia-Europe, North America and the Philippines. This is why there are so many volcanoes and hot springs all over Japan.

And by being right on the Pacific Ring of Fire , every century, Japan suffers from a few powerful earthquakes that are devastating. In its history, the land of the rising sun has experienced about 200 earthquakes accompanied by tsunamis occurring below or right next to the Pacific Ocean.

But tall buildings in Japan are not ordinary buildings. All buildings - even small or temporary buildings - must be earthquake resistant in this country - Jun Sato, structural engineer and associate professor at Tokyo University.

Buildings can move

Buildings in Tokyo, Osaka and Yokohama occupy most of the cityscape around them. The towers give us the impression that they are solid structures and no man-made immortality.

It is a fixed background image of daily urban life in Japan, just like any major developed city in the world.

As people and transportation systems hustle around, the buildings are still and standing still - they are the key point to bring the vibrant city together. It was not until the earthquake, that people realized this view is illusion. Because in Japan, buildings can move.

Skyscrapers in Japan are not ordinary buildings.

The 2011 Japan earthquake is arguably the most devastating in recent times. The magnificent 9-magnitude earthquake in Japan on March 11, 2011 was the result of massive geological movements around the Pacific "Ring of Fire" .

The total force of power generated from the magnitude 9 earthquake in Japan on March 11, 2011 is equivalent to the explosion of 6.7 trillion cubic meters of TNT and about 1,000 times the destructive power of all Both nuclear weapons in the world combined.

This earthquake once again shows that the Pacific "Ring of Fire" is always implicitly unpredictable. But that is just one of many seismic occurrences in Japan every year.

According to experts, the reason why Japan often suffers earthquakes is because of its position. Japan is located along the Pacific Ring of Fire. This is an area where frequent earthquakes and volcanic eruptions occur.

This "ring of fire" is an area of ​​frequent earthquakes and volcanic eruptions surrounding the Pacific basin. It is shaped like a horseshoe ring and is about 40,000 km long, associated with a continuous range of ocean trenches, archipelagic arcs, volcanic ranges and the movement of tectonic plates. Sometimes it is also called the Pacific seismic belt.

About 71% of the world's most powerful earthquakes take place at the ring of fire. It passes through Samoa, Indonesia and Peru. Earthquakes often occur in Japan because this is one of the areas with the most active seismic activity. 20% of the magnitude of the magnitude 6.0 or more earthquakes in the world is in Japan.

According to the US Geological Survey (USGS), in fact, 81% of the world's strongest earthquakes occur in the Pacific Ring of Fire. Because Japan lies on a tectonic plate, the plates often separate and collide, leading to eruptive earthquakes and volcanoes.

There are 2 levels of earthquake resistance that engineers must perform. At the first level, the building must withstand small earthquakes that can meet about 3 to 4 times in Japan.

With these earthquakes, the occurrence of damage that requires repair is unacceptable. Therefore, the building needs to be so well designed that it can undergo earthquakes without any harm.

The second level is that the building can withstand extreme earthquakes, which rarely occur. This standard was set up based on the 1923 big Kanto earthquake, which was 7.9 meters high, destroying Tokyo and Yokohama, killing more than 140,000 people.

With stronger earthquakes than this, the goal is no longer to preserve buildings; Any damage is acceptable, as long as it does not cause human injury. Ziggy Lubkowski, seismologist at the University of London, said: "You design buildings to protect human life. That is the minimum requirement."

Energy absorption and damping technologies

To withstand the extreme forces from the earthquake, the building must absorb as much seismic energy as possible. When a structure can absorb all the energy (from the earthquake), it will not collapse. This mainly happens in a process called seismic isolation .

Kyushu Expressway was damaged because of the magnitude 6.4 earthquake in 2016.

The building or structure is built in a form like bearings, or dampers - sometimes as simple as rubber blocks 30-50cm thick - to counteract earthquake-induced movements. Wherever the building columns are closed, they are located on the rubber sheets.

Adaptation from the building foundation is one of the basic ways that buildings are built to stand firm in earthquakes. But dampers that fluctuate throughout the building height can also enhance the ability to withstand earthquakes.

Lubokowski analyzed: "A tall building can move 1.5 meters but if you set the shock absorber to some extent - for example, every 2 floors from the foot to the top of the building - you can reduce the knife. The shock absorber is like a bicycle pump, only the inside is full of liquid instead of air, when you compress the pump, it pushes It doesn't push very hard, but it will move a bit, this process can reduce fluctuations in the building. "

Complex devices that absorb energy from earthquakes and reduce vibrations are not the only way to help the building withstand earthquakes. Among other methods is also thanks to the structure and design of the building itself.

The grid structure is used at Hakodate Future University, designed by Riken Yamamoto.

Lubkowski said: "The ideal thing we want is to make the building as normal as possible. If each floor has the exact same height and all the bearing columns are separated at regular intervals like one. the network will better support the earthquake. "

But usually the designers of spectacular buildings are reluctant to compromise, and the conflict between seismic resistance required by engineers and the architect's vision of creativity often occurs.

Norhihiro Ejiri, Representative Director of Structural Engineering Company Ejiri, commented: "There is always a great conflict between us. Fortunately, in Japan, architects are also trained in earthquakes, so engineers and designers can discuss together and have a common voice ".

Skytree Tower in Tokyo is the second tallest structure in the world. It is built in the "new hybrid" style , combined with elements of traditional Japanese temple architecture, and has a central pillar connected to seismic shock absorbers, to both of these parts. can absorb energy from earthquakes.

Jun Sato, a researcher who developed both effective and elegant seismic engineering solutions, said: "When I discuss structural design with architects, I always look for ways to harmonize anti-elements. Seismic into the overall design of the building Sometimes I can find a way to embed those elements in the floor plan drawing design, sometimes I can create transparent or translucent elements. I can look at drawings that outline their geometric structure from which to develop seismic elements. "

For example, using a grid structure can avoid buckling the building support frame. If a part is buckled, the next part will help prevent bending and energy absorption will be divided into other parts.

As a result, the grid structure - looks very beautiful too - helps reinforce buildings. The goal of building buildings capable of withstanding earthquakes is not static. The researchers estimated the magnitude of the earthquake will affect the building through observing the current error.

However, the strength of the earthquakes in the region seems to be increasing, so predictions become more difficult, Ejiri said. Will future buildings be able to withstand the most intense earthquakes that are unharmed?"Yes, such buildings can come true. Thanks to the background isolation system, bearings, braces, and power reduction systems that we use, buildings will achieve that ability," Lubkowski commented. comment.

The answer lies in the regular testing of known technologies that we must stabilize the building, while continuing to experiment with more creative designs - such as grid structure.

Sometimes small test structures, such as complex polyhedrons, are designed to avoid bending in the Naoshima Pavillion, Kagawa (do Sou Fujimoto) project - can add to the knowledge base of engineers

Because natural disasters are often unpredictable, one cannot know whether a design can withstand the next earthquake until after the earthquake actually happened. Engineers and architects can only be sure of the viability of the design they create when disaster has already occurred.

In the past century, Japan has suffered over 24 intense earthquakes. In 1923 in Tokyo, the magnitude 7.9 earthquake killed more than 140,000 people. Or the 1995 earthquake in Hyogo Prefecture killed 6,427 people, injured more than 40,000, and nearly 400,000 houses collapsed, burnt or damaged.

Today, construction technology has developed dramatically, allowing Japan to have the most modern infrastructure system in the world. Buildings with large earthquake resistance are no longer rare.