da bridge

footing loads and horizontal support

the point of a catenary is that its supposed to be in pure compression, i.e the force vector at the footings should directed along the angle of the catenary at the footings.

need to get the data from our openscad model on the flash drive, but it looks like the angle is about 15 degrees.

Then given a supported load $B$, each footing supports $B/2$, and a coefficient of static friction $0.6$ implies that it will resist horizontal load $0.3B$

the horizontal force from the angle 15 degrees is $∼0.13B$ So the bridge should be secure without additional horizontal support, when placed on concrete.

basically we need coefficient of friction > $tan(θ)=0.26$

Friction of concrete against steel might be ~0.3-0.7? but it can be worse ?

What about if placed on soil? boussinesq solutions?