Instant bridge--just add disaster.

Florida International University installs an “instant bridge” in one morning. It lasts a whole 5 days before it falls on cars and pedestrians, killing an unknown number of people.

it was supposed to be completed in 2019 and be cable-suspended. what the hell did they think was going to support it in the meantime?

Sounds like some civil engineer slept thru his statics class…

Nauseatingly ironic quote from the article:

Damn thing didn’t even last a week.

I’m intensely curious what the engineering investigation will turn up. I hope it doesn’t degenerate into a counterproductive finger-pointing party.

and could be held personally liable (civil/criminal) if said engineer signed off on this as a PE.

it wasn’t nearly finished. it was meant to be a cable-supported bridge; one of the stories on the Miami Herald has a rendering of what it was supposed to look like. It appears they set the span into place across the end supports, but didn’t adequately support the span elsewhere while it was waiting for the cable suspension to be built.

[quote=“jz78817, post:5, topic:810618”]


That depends on who screwed up. If he had a solid design and assembly plan, but it wasn’t followed, then he’s off the hook. Something like that happened in Colorado in 2004, when a bridge girder buckled and collapsed during construction, decapitating the occupants of a car on the highway below it. The design was fine, but the construction crew screwed up the installation.

The Mayor says that there was some sort of stress test going on today. They didn’t stop traffic for it.

Miami Herald

Verified account


UPDATE: “There was some sort of test going on this morning,” says Miami-Dade Mayor Carlos Gimenez. “Some kind of work was going on at that bridge, a stress test.”

Here is a fairly high-rez photo. Looks like one of the end supports snapped (instead of collapsing from the middle, which is what I assumed.)

Here is a time-lapse video of the span being raised and moved into place last Saturday.

It’s a cable-stayed bridge, but it looks like the entire span was brought into place and installed without the cables in place, or any other support. I sure would like to know how they expected it to stay up.

Also, doesn’t this seem over-engineered for a pedestrian bridge? Why does it need a set of triangulated trusses and a set of cables?

Interesting. It’s a triangulated structure, so the top & diagonal members would be under compression, and the lower section under tension. And I think the stress would be higher at the ends. So to me, it seems to makes sense that a concrete structure would fail where there is maximum tension, i.e. the lower section at one end.

Disclaimer: my only experience with bridge design is countless hours spent playing Bridge Constructor.

Wow, the article at that link is kind of cringe-worthy now.

I’m surprised that it hasn’t been… erm… taken down.

I think we’re gonna have to put that test down as a fail.

The comment section is inadvisably still live, too.

Yes, it’s very odd indeed. Surely the cable stays are either essential or superfluous. If the design involves cable stays, how can it make sense to install the complete deck on one side of the central tower without any cables?

This article suggests something may have been dropped onto the bridge:

It’s a 950 ton bridge. It’s hard to see how a cable falling on it could cause the collapse.

Wait - was it the box that landed on the bridge or the cable? The bridge itself was supposed to have suspension cables, that weren’t installed yet, to bear the weight of the span. If the box was full of construction stuff, then the added weight landing unevenly on a bridge that isn’t correctly distributed might have overcome one of the supports.

AIUI, I mean.

Since this is Florida, presumably it was engineered to withstand hurricane force winds. Since we’re outside hurricane season, perhaps that explains why the span was (in principle) strong enough to be assembled without cable support, with cables to be attached later?