Thread by @zahed

A structural engineer’s view (yes, I was one) of the Antonovski bridge damage and why it has put it out of commission for the rest of the war (1/x)

https://twitter.com/ukraine_world/status/1552201554907873280

From the images I can see, this section consists of box girders, concrete elements designed to mimic steel girders over long distances. The holes you can see on the surface are bad enough… those distribute loads to vertical elements (2/x)

The concrete deck on top is primarily in a state of compression, which theoretically allows it to be repaired by professionals (i.e, not those repairing the bridge holes at Nova Kakhovka) (3/x)

This wouldn’t be an issue if the tension elements were unharmed (i.e., a steel bridge structure with a concrete deck). In such a case, the loads only span from beam to beam, a few meters at most. (4/x)

In this case however, the lower part of the box, the part in tension, has been seriously breached. Not only are the steel reinforcing elements doing all the work, but post tensioned elements have also been severed. What are those? (5/x)

Post tensioning is a delicate process that usually requires prefabrication due to the difficulties of adding tension to steel elements (big cables, not just rebar) on site. The PT is required for the long spans to be viable (and associated deflections to be minimal) (6/x)

The box girders, whether using PT elements or not, are designed to work as one unit. They can’t just be patched. This is just my observation from available images, but IMO this bridge is effectively out of action (7/x) #Kherson #Ukraine #HIMARS

Not to put too fine a point on it, but if they try to put loads on this section, there is a serious risk of collapse.

Will be fun to watch them try… (8/8)

One more thought… given the bridge design, it was inspired to target the center of the span and not supports (which can’t easily be struck from above). I recall the Bay Bridge in 1989…

The Kerch bridge has redundancy (probably by design) …another challenge altogether.

Ok, one more thought. Another advantage of box girders is torsional rigidity, the ability to withstand asymmetric loads - wind, but also traffic on one side.

Trying to use the undamaged edges of the bridge (the “wings” seen in this picture) will tip the span into failure.

Construction type confirmed here (I was right!): structurae.net/en/structures/…

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Ladies and gentlemen, my band from high school in the late 80’s (NSFW): soundcloud.com/thefurburgers/…