This is pretty convincing. I didn’t realise there was supposed to be a central column. Most bridge failures happen before the things are finished. The box-girder bridge failures are a classical example. When the box-girder is complete, you have a strong square tube. When it isn’t finished you have a set of smaller beams, with stress raising at every unfinished join. And there’s probably a crane sitting on it too.
Here’s how it’s done…
This one is 125 ft span instead of 175 ft, but it is only made of stone, and it was finished in 619 (yep, just coming up to its 1400th birthday). Looks nice too.
