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An Encyclopedia of the History of Technology part 91

An Encyclopedia of the History of Technology part 91. This one of a kind encyclopedia presents the entire field of technology from rudimentary agricultural tools to communication satellites in this first of its kind reference source. Following an introduction that discusses basic tools, devices, and mechanisms, the chapters are grouped into five parts that provide detailed information on materials, power and engineering, transportation, communication and calculation, and technology and society, revealing how different technologies have together evolved to produce enormous changes in the course of history | PART FIVE TECHNOLOGY AND SOCIETY He also designed a novel triple structure to give stability to his hemispherical outer dome and flatter interior one. His outer dome is constructed of wood covered with lead. Inside this is a pyramidal brick cone which supports the lantern while the inner decoratively painted masonry dome is seen from the interior. Wren s colonnaded drum with its continuous entablature supports the dome better than Michelangelo s drum at St Peter s but even so encircling iron chains were used now replaced by two stainless steel girdles. Modern domes The traditional domical covering has largely been abandoned in modern building but the technical development in materials of plastics steel and reinforced concrete have led to a wide variety of curved shell coverings to large structures particularly for auditoriums exhibition halls and sports stadiums. Such shells made of reinforced concrete may be used to span a space as great as Brunelleschi s Florence Cathedral but need to be only a few inches in thickness. For example in 1957 in Italy Pier Luigi Nervi who had been experimenting since 1935 with reinforced concrete employed it to cover his Palazzo dello Sport in Rome. In this building great Y -shaped structures transmit the weight and thrust of the dome to the ground. The geodesic dome invented by R.Buckminster Fuller and built for the United States display pavilion at the Montreal Expo 67 was almost spherical and had a maximum span of 76m 250ft . It was constructed of short struts of light metal this is usually aluminium and was covered by a plastic skin. The short structural elements were interconnected in a geodesic pattern that is by the shortest possible lines. Such domes ideal for use as factory buildings will withstand high winds and are very lightweight and may be quickly erected. CANTILEVER CONSTRUCTION In this type of structure the building element block beam or girder is fixed securely at one end by a downward force behind a fulcrum and .