5 ms·

The same thought went through my mind watching it, but you could say the same about most (many?) concrete structures. Someone with a structural background could

The same thought went through my mind watching it, but you could say the same about most (many?) concrete structures. Someone with a structural background could explain better, but I believe the rebar and concrete provide different kinds of strength, like concrete is compressive strong (and keeps the minimal amount of rebar from moving around and bending, while the rebar keeps the concrete from cracking. Even for the bike, it wouldn't be the same structurally if they just wired up a rebar frame

pwg 4y ago
> but I believe the rebar and concrete provide different kinds of strength Yes, concrete provides great compressive strength, but is not very strong given tensile loading. Rebar provides the tensile loading support that concrete alone lacks. See: https://en.wikipedia.org/wiki/Rebar https://en.wikipedia.org/wiki/Rebar
TheDudeMan 4y ago
Yes, but it doesn't matter for a bike. Riding it is not going to crumple that amount of rebar.
- stergios 4y ago
  The front left fork failed. You can see the crack in the video as he is riding. The front fork has a bending moment as well as compressive force. When the bending force was applied the concrete failed and the rebar did not. Overall, I really liked this as an art project. I'm not sure what the artist wants to communicate with the bike, but I found it very satisfying.
  - JKCalhoun 4y ago
    I'd like to think they're reminding us why we don't make bikes out of concrete (but we can!).
  - debacle 4y ago
    > I'm not sure what the artist wants to communicate with the bike "I paid a lot of money for an architecture degree I'm not using."
  - 2muchcoffeeman 4y ago
    How much of this can you just chalk up to using concrete and just copying the design of a normal bike? This is a fun art project but doesn't seem like much more. Sorry for being negative about an art project. I think I was projecting my own biases, but it sounded like an engineering project and then I didn't learn anything.
pkaye 4y ago
I took civil engineering a long ago in college but diverged on my career. This is what I recall. In reinforce concrete beams the bending causes compression on the top and tension on the bottom. Since concrete is weak in tension (maybe 1/10 of compression strength), the rebar at the bottom will carry the tension. When you do the design calculations, some approximations are made like concrete carries no tension on bottom half of beam and how the stress is distributed on the top portion. Then with iterative analysis you can converge on an solution. Then once you got the basic design, there will other rules like displacement, buckling conditions. Here is an example design calculation I could find: https://civilengineeringbible.com/subtopics.php?i=32 https://civilengineeringbible.com/subtopics.php?i=32

pwg 4y ago

> but I believe the rebar and concrete provide different kinds of strength Yes, concrete provides great compressive strength, but is not very strong given tensile loading. Rebar provides the tensile loading support that concrete alone lacks. See: https://en.wikipedia.org/wiki/Rebar https://en.wikipedia.org/wiki/Rebar

TheDudeMan 4y ago

Yes, but it doesn't matter for a bike. Riding it is not going to crumple that amount of rebar.

stergios 4y ago
The front left fork failed. You can see the crack in the video as he is riding. The front fork has a bending moment as well as compressive force. When the bending force was applied the concrete failed and the rebar did not. Overall, I really liked this as an art project. I'm not sure what the artist wants to communicate with the bike, but I found it very satisfying.
- JKCalhoun 4y ago
  I'd like to think they're reminding us why we don't make bikes out of concrete (but we can!).
- debacle 4y ago
  > I'm not sure what the artist wants to communicate with the bike "I paid a lot of money for an architecture degree I'm not using."
- 2muchcoffeeman 4y ago
  How much of this can you just chalk up to using concrete and just copying the design of a normal bike? This is a fun art project but doesn't seem like much more. Sorry for being negative about an art project. I think I was projecting my own biases, but it sounded like an engineering project and then I didn't learn anything.

pkaye 4y ago

I took civil engineering a long ago in college but diverged on my career. This is what I recall. In reinforce concrete beams the bending causes compression on the top and tension on the bottom. Since concrete is weak in tension (maybe 1/10 of compression strength), the rebar at the bottom will carry the tension. When you do the design calculations, some approximations are made like concrete carries no tension on bottom half of beam and how the stress is distributed on the top portion. Then with iterative analysis you can converge on an solution. Then once you got the basic design, there will other rules like displacement, buckling conditions. Here is an example design calculation I could find: https://civilengineeringbible.com/subtopics.php?i=32 https://civilengineeringbible.com/subtopics.php?i=32