About Traditional Japanese Houses
Japanese traditional houses, called 古民家 (kominka), are wooden structures aged 50 years or more, built using the traditional construction method known as "木造軸組工法" (Wooden Post-and-Beam Construction). These houses showcase traditional craftsmanship by avoiding the use of metal fittings. Pillars are placed directly on stones, and the joints between pillars and beams lack nails.
Why Are Traditional Houses Earthquake-Resistant?
In the 1995 Great Hanshin Earthquake, traditional houses proved more earthquake-resistant compared to houses built using conventional methods. The flexible structure of traditional houses, designed to release seismic energy, contributed to their resilience.
Wooden Framework (Traditional Construction Method)
Joinery Technique: Traditional construction employs a "ほぞ継ぎ" (hozo-tsugi) joinery technique, where convex "ほぞ" (hozo) on pillars fits into concave "ほぞ穴" (hozo-ana) on beams, connecting them without nails. Sometimes, wedges are used for additional fixation. This structure provides a "damping effect," reducing seismic forces during earthquakes. However, due to historical material limitations, flexibility was prioritized over resistance.
Role of "石場建て" (Stone Foundation): The foundation in traditional construction, known as "石場建て" (Ishibatate), involves pillars passing through stones without direct attachment. During earthquakes, the house slides on the stones, absorbing seismic forces. This unique structure aligns with Japan's seismic environment, acting as a form of seismic isolation.
Conventional Construction Method
In contrast, the conventional construction method relies on metal fittings to firmly secure pillars and beams. The use of anchor bolts in a concrete foundation provides stability during seismic events. However, this method lacks the flexibility seen in traditional construction, making it more susceptible to seismic forces.
Hybrid Construction in Contemporary Shrine and Temple Architecture
Modern shrine and temple constructions often blend traditional and conventional methods, incorporating elements like cross braces, metal fittings, and robust foundations. Additionally, the integration of cutting-edge seismic technologies contributes to enhanced safety and reduced maintenance requirements.
The earthquake resilience of traditional Japanese houses stems from the flexibility of traditional construction methods, combined with unique features such as wooden frameworks, earth walls, and stone base construction. While technological advancements offer stronger jointing mechanisms, the importance of flexibility was paramount in older constructions. This combination results in structures that effectively withstand seismic challenges, showcasing the significance of traditional elements in Japan's seismic landscape.
