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Towers and space trusses |
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Non-space enclosing structures such as towers, antennas, and scaffolds can also be |
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triangulated for strength and stability. Another one of the first structural uses for the octet |
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truss geometry was a twenty-five meter tall observation tower built in Nova Scotia by Dr. |
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Bell in 1907. Notice that the top of the tower is an octet truss that is sliced parallel to the |
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111 plane to form the viewing platform. The legs are sliced from the octet truss parallel to |
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the squared 100 plane. |
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Other freestanding tower designs can incorporate elements of the octet truss. Fig. 298 |
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shows two tower designs based on the octahedron. Fig. 298 a) is a lattice tower, called |
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Type A, comprised of octahedral cells joined face to face. Readers of the previous lesson |
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. |
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on crystallography will recognize it as being structurally identical to a section of the HCP |
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crystal lattice structure (a variation of the octet truss). Since the tower is completely |
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triangulated, it is inherently stable. Fig. 298 b) shows a tower, Called type B, built from |
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octahedra that are joined vertex to vertex. Vertical braces, or stays (green), are used to |
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position the octahedra upright. The unit cell of this structure, pictured in Fig. 299, is not |
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stable. Therefore it must be braced against torsional or twisting movement. This can be |
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done, redundantly, by cross bracing the face of the rectangular shaped sections with cable. |
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Back to Knowhere |
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