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Published byRalph Green Modified over 2 years ago

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Strength in Structure Created by Brian Domroes Rene’ Ehrhardt, Flickr

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What forces are at work here? Bill Lim, Flickr Frank Kovalchek, Flickr

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Tension and Compression

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Tension The force that results from things being pulled apart Compression The force that results from things being pushed together

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Which is the most stable?

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Increasing Stability

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More Triangles!

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Why is the triangle so strong? Balance of compression and tension Angles are fixed Key Compression (push) Tension (pull)

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Compression/Tension Example

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A system of triangles

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Geodesic Construction Enough class materials for 10 domes Domes will be assembled in groups of 3

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Strut and Connector Strut Connector

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Geodesic Construction Appoint a leader in each group Leader gives group members roles

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Measure Your Isosceles Triangle Measure in millimeters Measure from the middle of struts

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Geodesic Construction Do you notice forces working together? GENTLY press on connectors to check

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Do You Remember? Key Compression (push) Tension (pull)

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How can you offset tension?

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How do we anchor new triangles?

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How do you keep these triangles in place?

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And so on…

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A complete system of triangles The tension at the base… is offset by the compression at the joints

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Why is there no place like dome? Only manmade structure that gets proportionally stronger as it increases in size Martin Ujaki, Flickr

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Why is there no place like dome? Has the biggest enclosed volume to weight ratio for any manmade structure notfrancois, Flickr

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Why is there no place like dome? Green Very efficient with heating/cooling Uses less materials Withstands harsh weather Courtesy of Plantagon

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Do you see geometric shapes? andy_0306uk, Flickr

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Geometric Shapes Equilateral Triangle Isosceles Triangle Acute Triangle Hexagon Regular Pentagon Decagon (base of your dome)

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Do you see similar shapes? andy_0306uk, Flickr

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Two shapes are similar if: One shape is an enlargement of the original One shape is a shrinkage of the original

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Two shapes are similar if: Both shapes are congruent

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Two shapes are similar if: Corresponding sides are proportional 3 54 6 8 10

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Similar Shapes What is the missing value? 12 feet 4 feet ? 6 feet

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Similar Dimensions 16 inches 12 inches Original Dimensions S1S1 S2S2 New Dimensions (S 1 x S 2 ) Scale Factor (New to Original) to

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Challenge What are the lengths of the two isosceles triangles that you did NOT construct? ? ? ? ?

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3 Similar Domes Smallest dome height is 71 mm Medium dome height is 115 mm Large dome height is 184 mm

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Rules You may not share any information with other groups YOU MUST SHOW ALL WORK Everyone in your group should be able to explain

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If you finish early… Please take you dome apart carefully Read the stickers on the bags so you know how many parts go in each bag.

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Smallest Triangle Show your work

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Blue is 47 mm, Yellow is 42 mm ? mm 71 mm 75 mmsm bl sm ht md ht md bl = 115 mm Smallest Triangle 115 ÷ 71 ≈ 1.62 = scale factor for medium to small 75 ÷ 1.62 ≈ 46 mm = small blue

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Medium Triangle Show your work

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Medium Triangle Blue is 76 mm, Yellow is 68 mm 115 ÷ 71 ≈ 1.62 = scale factor for medium to small 47 x 1.62 ≈ 76 mm = medium blue 47 mm 71 mm 115 mm ? mm sm bl sm ht md ht md bl =

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Largest Triangle Show your work

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Largest Triangle Blue is 122 mm, Yellow is 108 mm 184 ÷ 71 ≈ 2.59 = scale factor for large to small 42 x 2.59 ≈ 109 mm = large yellow 42 mm 71 mm 184 mm ? mm sm Yl sm ht lg ht lg Yl =

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Today I learned… Possible Topics Forces Geometric shapes Similar Figures Solving Proportions Scale Factor Geodesic Dome

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The World Of Triangles. Triangles A triangle is a 3- sided polygon. Every triangle has three sides and three angles. When added together, the three angles.

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