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The location where an earthquake begins is called the hypocenter, and the area directly above the hypocenter is called the epicenter. The region where the ground shaking is most intense during a destructive earthquake is called the metronomena, which are often the same areas where the epicenter is located. Earthquakes often cause serious casualties and can trigger fires, floods, leaks of toxic gases, the spread of bacteria and radioactive materials, and may also cause secondary disasters such as tsunamis, landslides, collapses, and ground fissures.
What is the interior condition of a wooden house during a simulated strong earthquake?
Currently, the seismic design of earthquake-resistant buildings is mainly based on the provisions of the "Code for Seismic Design of Buildings". High-rise buildings should also comply with the seismic requirements of the "Technical Specification for Concrete Structures of High-Rise Buildings". Simply put, insufficient seismic fortification standards, improper design, poor construction, and inadequate use and maintenance, coupled with a lack of disaster prevention awareness, mean that the collapse of a building is often the result of the superposition of multiple factors. If two or more factors are present simultaneously, the likelihood of disaster increases significantly.
As a country with a history of five thousand years, China has long made full use of earthquake-resistant buildings. Unlike other countries in the world that mostly use stone to build buildings, the Chinese nation not only wisely chose wood as the main building material from the beginning of civilization, but also developed the world's oldest, longest-lasting, and most technologically mature structural system - the flexible frame system.
Flexible framework system
If we only consider the Hemudu site in Yuyao, Zhejiang Province, the development of timber structure technology in my country dates back at least seven thousand years. In contrast, the West used load-bearing wall systems for thousands of years until the Industrial Revolution and the development of modern science and technology, when the superiority of frame structures was realized and they began to be widely adopted. What is even more interesting is that this frame system is still "hard against hard".
Unlike the Western approach of "using rigidity to overcome flexibility," flexible frame systems employ various ingenious measures to resist earthquake impacts, aiming to minimize the destructive power of nature at the lowest possible cost. Many ancient Chinese buildings have successfully withstood major earthquakes, such as the Guanyin Pavilion of Dule Temple in Jixian County, Tianjin, and the Wooden Pagoda of Yingxian County, Shanxi, which have stood resiliently through numerous quakes over the centuries. Contemporary architectural design aims to withstand earthquakes of magnitude 9, and flexible frame systems can largely meet this requirement at a significantly lower cost than the rigid approach of Western systems. The core of this system lies in maximizing the use of wood.
The wall fell but the house did not collapse.
In a flexible frame system, all the loads on the upper part of the building are borne by the framework, with the columns and beams acting as load-bearing structures. The walls, however, do not bear weight. A room is formed by four columns supporting beams and purlins. In this type of frame structure, the walls are used only to separate interiors and exteriors, dividing space like a curtain. The renowned architect Liang Sicheng also pointed out that "in European architecture, only modern steel and reinforced concrete frames are in principle the same as this wooden frame structure," meaning that modern frame structures also draw inspiration from traditional Chinese wooden structures.
The left picture shows Liang Sicheng.
In modern timber-frame construction, the steel nail connections between OSB boards and dimensional lumber installed on the timber joists provide a load dissipation path during earthquakes. This flexible connection gives the entire building considerable elasticity and a degree of self-recovery capability; even if individual connections fail, adjacent nodes provide support to prevent the overall structure from collapsing. Furthermore, increasing the thickness of the OSB boards, the size of the joists, and the number of nails can add even more protection to timber-frame buildings.
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New Zealand, a country located on the Pacific Ring of Fire, has largely adopted wooden structures for its houses of six stories or less after the devastating Christchurch earthquake in 2011. Those who have traveled there must have been impressed by the diverse architecture, warm fireplaces, and beautiful scenery.
Traditional Chinese architectural techniques have not only been well preserved with the development of the times, but are also increasingly favored by modern people. Wooden structures will be the future trend.