3 ms·

I'm not sure you're talking about the same thing though, I think they meant these thermal expansion joints, not necessarily a bridge made from metal mesh: http

I'm not sure you're talking about the same thing though, I think they meant these thermal expansion joints, not necessarily a bridge made from metal mesh: https://i.pinimg.com/originals/4d/82/91/4d8291e022bd14c87985df11fad1be1e.jpg https://i.pinimg.com/originals/4d/82/91/4d8291e022bd14c87985... I know that picture is a mesh, I thought it had the best detail, but they're on paved bridges too: https://siamagazin.com/wp-content/uploads/2018/03/23h32h-min-1.jpg https://siamagazin.com/wp-content/uploads/2018/03/23h32h-min...

hinkley 3y ago
I think they meant the former, because otherwise having expansion joints that don't expand doesn't really accomplish anything. The concrete still expands, hence the need for the joints.
- maxbond 3y ago
  My reading is that they were saying this expansionless material isn't likely to be useful for bridges, because thermal expansion is well managed by these traditional techniques. I agree though that both the thermal coefficient of the teeth probably don't impact their performance (the expansion in the teeth relative to the width of the gap is negligible, so we can probably pretend we're using expansionless teeth already), and I've never had an accident on one of these bridges, but I'm sure you're right and that the mesh concentrates the force on your bones like a golf club.
  - pfdietz 3y ago
    And because this material is 35% nickel. Nickel costs $21/kg.
- jaclaz 3y ago
  The whole idea with reinforced concrete is that concrete has thermal expansion very similar to that of steel, thus both steel rebars and the concrete that encloses them move in the same manner. A rule of the thumb with bridges is that the movements (thermal expansion/contraction + elongation or contraction due to loads + in case of pre-stressed concrete fluage/creep) is in the range of 6-9 mm every 10 m. Expansion joints on (long) continuous beam bridges can thus need to have very large displacement, up to 1,200-1,400 mm are relatively common.

hinkley 3y ago

I think they meant the former, because otherwise having expansion joints that don't expand doesn't really accomplish anything. The concrete still expands, hence the need for the joints.

maxbond 3y ago
My reading is that they were saying this expansionless material isn't likely to be useful for bridges, because thermal expansion is well managed by these traditional techniques. I agree though that both the thermal coefficient of the teeth probably don't impact their performance (the expansion in the teeth relative to the width of the gap is negligible, so we can probably pretend we're using expansionless teeth already), and I've never had an accident on one of these bridges, but I'm sure you're right and that the mesh concentrates the force on your bones like a golf club.
- pfdietz 3y ago
  And because this material is 35% nickel. Nickel costs $21/kg.
jaclaz 3y ago
The whole idea with reinforced concrete is that concrete has thermal expansion very similar to that of steel, thus both steel rebars and the concrete that encloses them move in the same manner. A rule of the thumb with bridges is that the movements (thermal expansion/contraction + elongation or contraction due to loads + in case of pre-stressed concrete fluage/creep) is in the range of 6-9 mm every 10 m. Expansion joints on (long) continuous beam bridges can thus need to have very large displacement, up to 1,200-1,400 mm are relatively common.