>>23446752
>There's random ass asteroids and meteors randomly flying through space
>random
Key word, they aren't, even the small ones. We can already track billions of space debris 10mm in size.
So it wouldn't be a problem whatsoever to detect by a civilization that's now used to moving asteroids around.
And to resist occasional pebbles you don't need the ability to resist a nuke.

>And what costs when most of the material is gotten from the asteroid belt
I take it you've never worked in a big company. The cost is the manpower, the energy, the equipment, and the time spent on doing that instead of building other colonies.
I can already imagine the meeting:
"We need to build colonies for 11 billions peoples in 70yrs and you want to make them Nuke-proof? Maths say we could only make 5 billions that way. And why? We don't even have other countries to declare war to anymore? Are you planning a war?"

Gundam didn't reach post-scarcity and Earth is fucked up by MAN'S HUBRIS causing global disaster.

>Of course suspension bridges aren't meant to withstand nukes. They're also not made with space materials
And why would they need to withstand nukes if made with "space materials"?
Getting materials is the least of the problems for bridge construction. Refining them now that take time, we build suspension bridges because it's either impossible, unpractical, or far more costly (in manpower/time) than doing it with any other design.

>made to last for centuries in space
Thicker structure is the wrong methods of achieving that, you'll increase structural fatigue (especially with tensile strength) and make it harder to replace parts when you inevitably need to for various reason, and it won't make it cheaper in maintenance.

>asteroid colonies
1) any asteroid material you haven't processed is not structurally stable, a nuke would create seismic waves breaking everything inside. Asteroids are actually kind of fragile.
2) a mining colony isn't built for comfort, it's a sacrifice.