geodesic dome.pptx

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Geodesic dome

A geodesic dome is a spherical or partial-spherical shell structure based on a network of great circles ( geodesics) lying on the surface of a sphere. The geodesics intersect to form triangular elements that have local triangular rigidity and also distribute the stress across the entire structure. When completed to form a full sphere, it is known as a geodesic sphere.

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Geodesic Dome Types for skylights

Basically, Geodesic domes are produced by subdividing the faces of a regular polyhedron that fits onto a sphere. Geodesic spheres and domes are then categorized according to the base polyhedron, the number of subdivisions and the type of subdivisions.

Base polyhedron There are several regular polyhedrons that can be used as a basis for subdividing into geodesic spheres but 3 are more common. The most common one is the icosahedrons, the second one is the octahedron and then the less commonly used is the tetrahedronen.wikipedia.org/wiki/Geodesic_dome

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COMMAN POLYHEDRON

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Icosahedrons

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Octahedrons

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Tetrahedrons

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Construction Issues

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Loads distributionsA geodesic dome uses a pattern of self-bracing triangles in a pattern that gives maximum structural advantage, thus theoretically using the least material possible. (A "geodesic" line on a sphere is the shortest distance between any two points.) Local loads are distributed throughout the geodesic dome, utilizing the entire structure. Geodesic domes get stronger, lighter (qt movie, 2.6mb, no sound), and cheaper per unit of volume as their size increases--just the opposite of conventional building.

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Geodesic Load DistributionsStruts: Struts are the force members in a geodesic dome that act in compressive and tensile forces to resist loading. What exactly is geodesic? Geodesic is a Latin term meaning earth dividing. Imagine the earth as a perfect sphere, with its longitudinal lines dividing it into equal halves. These longitudinal lines are called great circles. The geodesic dome has members which follow three sets of principal sets of great circles intersecting at 60 degree angles, subdividing the dome surface into a series of equilateral spherical triangles. The more complex this system of triangles, the more spherical the dome becomes. The structure as a whole is subjected to bending moments, but the individual struts are rigid and only subjected to tension and compression forces. Applied loads are distributed through one strut to the pins. The pins transfer the loads to the next strut, and this process continues until the loadings reach the foundation. A diagram of the load 2/16/13 is distribution

Pins: The pins are used at vertices to hold the struts together. The pins must be able to resist the compressive forces transferred through the struts. All of the vertices must have a pin connection, which allows forces to be transmitted through to the foundation. The pins should be weather treated to resist damage due to environmental conditions Substructure: The foundation transfers loads from the superstructure down into the earth. The applied loads consist of live, dead, wind, seismic, and gravitational. All of these must be withheld by the foundation. Although the geodesic dome is primarily a self-supporting structure, its foundation must carry the applied loads and anchor it into the earth. Typically, a circular concrete slab is poured onto the earth. The struts and piers are bolted and welded to the slab as shown in the diagrams below:

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Dome models

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