The Shimizu Mega-City Pyramid is a conceptual scheme for the construction of a massive, pyramidal open-air truss over Tokyo Bay in Japan (Fig. 5). The gigantic truss would be able to support the weight of two dozen eighty story skyscrapers hung from critical truss joints. The structure would be over 3,000 feet high and would house 750,000 people. Its footprint would cover the area of 275 Tokyo city blocks. If materialized, it would be the first offshore city ever built and the largest man-made structure on earth. The Shimizu Mega City Pyramid is proportionately identical to the ancient Egyptian pyramids. However, it is 55 times larger than its ancient inspiration and hollow lacking the unyielding appearance of the solid stone Egyptian pyramids. It bears more resemblance to the Luxor Hotel in Las Vegas, Nevada built in the mid 1990s with the exact match dimensions of the ancient pyramids. The Luxur Hotel (Fig. 6) has the largest glass enclosed atrium in the world and serves as a dry run for the Mega City Pyramid. Wind tunnel tests for the Luxur Hotel showed that a dangerous vortex of wind usually occurs on the leeward side of the pyramid, causing a drastic drop in air pressure that could pull the heavy glass curtain off the building. Engineers had to redesign the glass curtain attachments to withstand wind turbulences on the Pyramid surfaces. Wind test results of the Luxur Hotel guided the exposed truss design of the Mega City Pyramid, which would be totally open to the elements, allowing wind to blow throughout the structure. This would drastically reduce wind impact on the Pyramid and improve the structure’s ability to withstand powerful typhoons in the Pacific. Only habitable spaces within skyscrapers and circulation channels would be enclosed. Despite such an open truss design, the weight of the steel trusses of a 3,000-foot-high pyramid, 24 skyscrapers, and all other facilities that service 750,000 people would exceed trillions of pounds. According to the design scheme, the pyramid weight would be supported on 36 massive columns sunk in Tokyo Bay. Each column must be able to handle 50 million tons, which is more than 50 times the weight of the Golden Gate Bridge. The weight of the proposed structure is so large that it cannot be built with currently available materials. The Mega City Pyramid design relies on the future availability of superstrong, lightweight materials based on carbon nanotubes. These are nanoscale cylinders of carbon with a lattice of carbon atoms, each of which is covalently bonded to three other atoms. The structure of a nanotube can be imagined as a sheet of graphite rolled into a tube akin to a sheet of chickenwire. It buckles, but does not break and can be straightened back without any damage. When perfected, carbon nanotubes are expected to be vastly lighter, stronger, and longer lasting than steel. Mixing nanotubes with plastic and metal can give them extraordinary strength, creating a new generation of superstrong and super-lightweight composites that would make steel obsolete. Construction logistics for such a giant building is beyond the capacity of even the most accomplished construction companies in existence. No cranes or hoisting mechanisms in operation today can jack these massive structural members into place. The design scheme calls for spider-shaped, robotic plants that would spin a web of massive trusses, transforming carbon and other materials into miles of support right on site. Dante Bini proposed an air-induced hoisting system to lift millions of pounds of trusses into position. Bini spent a good deal of his career designing and building large, reinforced concrete domes, replacing cumbersome scaffolding with an air-lifting mechanism. In 1967, he laid out a large, inflatable membrane on the ground and topped it with a web of reinforced steel held in position by a network of high-tension steel springs. Almost 300 tons of wet concrete followed, which was covered by a second membrane to hold it in place. Defying structural logic at the time, Bini pumped air under the first membrane, and a large dome shell was shaped into place in less than an hour (Fig. 7). Following several successful attempts in the United States and Australia, Bini has built hundreds of such domes around the world. He proposed to use a similar system to lift the massive truss members of the Mega City Pyramid into position (Fig. 8). The idea is to build a square truss base on location and then connect the corners diagonally with telescopic expandable truss shafts that will be jacked into place by an inflated balloon placed underneath. The most innovative aspect of the Mega City Pyramid design concept is its three-dimensional transportation system. The truss members forming the pyramid are hollow, with an internal space large enough to allow trains and cars to move freely between different parts of the city; structural members double as the city highways or subway tunnels. Trusses connect at hollowed spheroid nodes, which would provide structural support and serve as transfer points for travellers (Fig. 9). Residents and visitors could also connect to an outside transportation system that carries them to the heart of the city of Tokyo. Transit options would include accelerating walkways, inclined elevators, and a personal rapid transit system where individual, driverless pods called “ULTra” would travel within the trusses. Heathrow Airport in London recently adopted the ULTra (Fig. 10) Personal Rapid Transit (PRT) to provide better access to its terminals. Each pod can fit four passengers and travels along guide way networks. Powered by an electromagnetic grid imbedded underneath guideways, ULTra is an on-demand, driverless car summoned to the rider location and not vice versa. It is an environmentally friendly form of transportation that saves more than half the fuel used by current private and public transportation systems (ATS).
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