Hacker News

Thanks for the quick summary

The pictures on page 25 seem to show how this socket design fails. First because they didn't evenly distribute the wires in the socket (seriously??)... And second, the shear on the zinc from the compressed wire bundle is essentially a narrow rectangle in the direction of the cable with almost all the force concentrated in a narrow forward bit, not really distributed evenly through the socket, because of the wire ends splaying outward and not being equally distributed. I guess the idea is the rest of the zinc towards the back provides a counter force on the front part, but there's a whole lot more zinc in the back pulling on a smaller amount in the front. The tight bundle and the conical shape is great for a tight install, but doesn't help distribution of load. Compare to the Golden Gate Bridge wire termination (https://c7.alamy.com/comp/2RY9PKW/golden-gate-bridge-plans-i...). The zinc creep is definitely bad, but it seems made worse by an uneven distribution of load in the socket, in addition to all the other problems...

tl;dr once the outer wires break in the socket (in part due to zinc creep, but also potentially more load on them), the "glue" keeping the wire bundle connected to the socket is broken, the former wedge keeping the core in place becomes a straight line, and you have a core ready to pop out.

When those cables go... dang that's a lot of tension.

Much better, AI generated "summary" pages are not a good link for this story.

This is the better link. The meat is on page 2.

> Long-term low-current electroplasticity, induced by the electromagnetic waves from the Arecibo telescope itself, may have sped up the zinc creep, it says.

I presume we aren't using most bridges as interstellar antennas.

My guess is the safety factor here was lower than typical, causing the failure mode to occur.

I expect future bridges will design these joints even more conservatively because they were skating closer to the edge than they realized.

They also mentioned that this is the first example of the unknown phenomena that caused the creep. This technology has been in use quite successfully for more than 100 years.

This would predict that we should be seeing far more mystery collapses than we do though

Bridges probably shouldn't be subject to the same electromagnetic radiation that gets focused by the telescope though so ideally not a problem there.

it had already been decommissioned prior to the collapse. Yes, decommissioning does indicate funding is being cut, but it was unrelated to the collapse.