Expo 2025 Osaka, Kansai Special - Demolition Kingdom

Key Concepts

• Grand Ring: The world’s largest wooden architectural structure (Guinness World Record), serving as the symbol of Expo 2025.
• Laminated Wood: A structural material created by gluing layers of wood together, offering strength comparable to steel.
• Slinging: The critical technical process of attaching wires/cables to a load for crane lifting; requires precise tension management.
• Nuki Technique: A traditional Japanese construction method where pillars and crossbeams are joined to support each other.
• EPS Method: A foundation technique using lightweight styrofoam to prevent sinking on reclaimed land.
• FRP (Fiber Reinforced Plastic): A lightweight, durable material used in pavilion construction to meet weight restrictions.
• Upcycling: The process of transforming waste materials (like pavilion membranes) into new, functional products.

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1. The Grand Ring: Engineering and Demolition

The Grand Ring is a 2 km long, 20 m high wooden promenade. Its construction utilized 70% domestically grown cypress and cedar.

• Construction Methodology: Built in modular units to allow for precision assembly. It employs the Nuki technique, which provides structural flexibility during earthquakes.
• Demolition Strategy: Unlike standard demolition, the goal is reuse. Approximately 60% of the structure is being dismantled piece-by-piece to be repurposed for future projects, such as the Noto earthquake recovery and an international garden festival.
• Technical Challenges:
  • Weight Imbalance: Wood absorbs moisture, making the actual weight of components unpredictable.
  • Joint Complexity: The structure features 3 cm thick steel plates within joints that must be pulled free simultaneously without damaging the wood.
  • Wind Sensitivity: Because the components are relatively light (approx. 3 tons), they act like kites, making crane operations dangerous in windy conditions.

2. The Netherlands Pavilion: Innovation on Reclaimed Land

The pavilion was built on Umeishima, a man-made island, necessitating strict weight management to prevent the structure from sinking.

• Foundation: Engineers utilized the EPS method, placing a layer of styrofoam beneath the foundation to reduce load.
• Material Choice: The use of FRP allowed the structure to be 20% lighter than initial estimates.
• Sustainability: The pavilion is being fully relocated and reconstructed elsewhere, demonstrating a commitment to circular architecture.

3. The Role of Fukushima in Sustainable Construction

The laminated wood for the Grand Ring was produced in Namie, Fukushima, a town recovering from the 2011 earthquake and nuclear disaster.

• Manufacturing Efficiency: A high-frequency press machine reduced the gluing time for laminated wood from 8 hours to approximately 10 minutes, enabling the mass production required for the Grand Ring.
• Social Impact: Supervisor Assada Hideo led the production, insisting on using local Fukushima timber to revitalize the region’s forestry industry and combat prejudice against local materials.

4. Upcycling and Circular Economy

The expo emphasizes "reuse" as a core theme.

• Case Study: The roof of the Luxembourg pavilion (a 700-square-meter membrane) was upcycled into bags.
• Process: Artisans use a "ski" (shaving) technique to thin the material while preserving the core fibers, ensuring the resulting bags maintain the strength required for their original architectural purpose.

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Key Arguments and Perspectives

• Slinging as a Critical Skill: Expert steeplejack Noda Kenta argues that slinging is more vital than crane operation. Proper slinging—adjusting wire lengths by mere centimeters—prevents loads from swinging or bursting upward, which could cause fatal accidents or structural damage.
• Demolition as a "Grand Relay": The project is framed not as destruction, but as a transition. By dismantling structures intact, the expo passes on the "memories" and materials to future generations, turning the end of the event into a new beginning for the materials.

Notable Quotes

• "Slinging makes or breaks it. That's common sense. Everything we see around us was made thanks to slinging and slinging specialists." — Noda Kenta, Steeplejack Leader.
• "I wanted to use trees from my hometown. I absolutely had to use local trees to make the wood. My heart was set on that." — Assada Hideo, regarding the Fukushima timber used in the Grand Ring.

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Synthesis

The demolition of Expo 2025 serves as a masterclass in circular engineering. By prioritizing the preservation of materials through precise, manual dismantling techniques, the project avoids the waste typical of large-scale events. The integration of traditional Japanese joinery (Nuki) with modern high-frequency manufacturing and upcycling initiatives highlights a shift toward sustainable, long-term architectural lifecycles. The success of this mission relies heavily on the specialized skills of craftsmen who treat demolition with the same level of technical rigor as original construction.