7290db9c9e2820944358934a2b0200057980a9e7
bridge.org
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| 1 | +da bridge |
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| 2 | +* footing loads and horizontal support |
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| 3 | +:PROPERTIES: |
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| 4 | +:ID: 411fb925-2fe6-418e-9bcb-82bbb5d034cc |
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| 5 | +:END: |
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| 6 | +the point of a catenary is that its supposed to be in pure compression, |
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| 7 | +i.e the force vector at the footings should directed along the angle of the catenary at the footings. |
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| 8 | + |
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| 9 | +need to get the data from our openscad model on the flash drive, |
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| 10 | +but it looks like the angle is about 15 degrees. |
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| 11 | + |
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| 12 | +Then given a supported load $B$, |
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| 13 | +each footing supports $B/2$, |
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| 14 | +and a coefficient of static friction $0.6$ implies that it will resist horizontal load $0.3B$ |
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| 15 | + |
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| 16 | +the horizontal force from the angle 15 degrees is $\sim0.13B$ |
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| 17 | +So the bridge should be secure without additional horizontal support, when placed on concrete. |
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| 18 | + |
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| 19 | +basically we need coefficient of friction > $\tan(\theta)=0.26$ |
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| 20 | + |
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| 21 | +Friction of concrete against steel might be ~0.3-0.7? |
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| 22 | +but it can be worse ? |
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| 23 | + |
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| 24 | +What about if placed on soil? |
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| 25 | +[[id:1d521a37-86e1-4b38-9fca-f6bdd5cd96bf][boussinesq solutions]]? |