How Ukraine blew up a major Russian bridge

Last month, a truck loaded with explosives crossed the Kerch Bridge, a critical artery linking Russia with its troops fighting in southern Ukraine.

A train was traveling alongside.

The truck exploded in a critically vulnerable spot:

halfway between a pair of reinforced concrete pillars, which maximized road damage.

In what appears to be either a masterstroke of planning, or a pinch of luck, the explosion was large enough to break fuel tanks of the passing train, setting it on fire.

The blast was also well placed to rip the causeway even further out of its seams and throw it overboard.

The attack was a critical moment in the war.

He dealt an embarrassing blow to the president of Russia, Vladimir Putin, who presided over the opening of the bridge in 2018, underscoring Russia’s failure to protect a key strategic asset and a powerful symbol as the only link to Crimea.

Structural and explosives experts who examined the bridge’s design and images of the explosion offered new details on how the bridge was damaged.

The success of the operation demonstrates a sophisticated planningthey said, or luck.

There are few direct parallels to such a spectacular act of sabotage on a bridge behind enemy lines in wartime.

“Bringing down bridges was very difficult before the advent of precision-guided weapons, and even then it’s no easy feat,” said retired Rear Admiral Samuel J. Cox, director of the Naval History and Heritage Command in Washington.

“Given the historical difficulty, the damage to the Kerch bridge is quite impressive.”

Bridges are designed with greater strength than is typically needed so that they can withstand unexpected stresses, such as a weather event.

Even a powerful explosion can cause minimal damage if it hits in the wrong place.

The Kerch Strait Bridge is no exception, and its design is nothing special:

with a length of approx 11 kilometers, the causeway is supported by long steel beams resting on reinforced concrete pillars, sunk into the seabed.

A raised portion, known as a tied arch bridge, allows shipping traffic to pass underneath.

Despised by Ukrainians, the bridge was opened in 2018 as a symbolic link with Russia after the occupation of Crimea.

More recently, he served as critical power line for the Russian war effort.

Experts who examined images of the explosion agreed that the damage was most likely caused by a bomb truckas the Ukrainian authorities have claimed, and not by a missile launched from a ship under the bridge, as some have suggested.

They also agreed that the position of the truck when it exploded – between the structural supports that could have reduced the damage – was crucial in demolishing the span that supported the road bed between those two supports.

“Many things had to work perfectly for this to happen,” said Vijay K. Saraf, principal engineer at Exponent.

The blast set a train carrying large fuel tanks on fire on an adjacent bridge, creating flames and a plume of smoke.

And on the roadbed, the damage was not limited to the section between the supports: apparently with the precision of a demolition charge, the explosion was also perfectly positioned to cut or destroy some 275 meters of continuous roadway on the Russian side. of the long lower sections of the bridge.

But experts differ on whether the sequence points to a sophisticated plan.

Attack planners may have expected the fuel tanks to explode and inflict significant damage to the railroad bridge, said Adam Evans, a structural engineer at Wiss, Janney, Elstner Associates.

But he said the blast was unlikely to have been intentionally timed at an optimal point to cause damage to the road.

“I would find it hard to believe,” Evans said.

“I think it’s probably more like:

“We’re going to put a bomb on this bridge and it’s going to cause a lot of damage.” “

Indeed, according to several engineers, the damage from the explosion could have been greater if the bomb had exploded a minute or two later.

The truck had already started up the slope towards the wide raised section of the bridge, supported by a series of tall steel arches.

According to the engineers, a large enough explosion could have damaged the bows and rendered them unusable. the whole bridge from the street

“It almost feels like it was a mistake that it blew up where it happened,” said Shankar Nair, a Chicago-based structural engineer with more than 50 years of bridge design experience.

This raises questions about how the explosion was timed and whether the driver of the truck knew about the bomb’s existence.

A remote detonation may be difficult to time accurately.

But a suicide bomber could have waited until the truck reached the arch, Nair said.

A direct hit on the bow, with its massive amount of steel, could have taken much longer to repair, he said.

“Had it been a suicide truck bomb,” Nair said, “I think the guy would have destroyed the main span.”

However, the bomb’s trigger is still unknown.

Suicide bombers often behave erratically and it is unclear whether the truck bomb used was large enough to bring down the arched section of the bridge.

Russia quickly restored road and rail traffic on parts of the bridge, but the restoration to full capacity could take until next year.

A satellite image taken last week by Planet indicated that a large section of the roadway was still missing.

And the British Defense Ministry, citing Russian statements, said on Wednesday that road traffic could be disrupted until March 2023 and rail traffic until September 2023.

Regardless of how long the bridge has been damaged, the attack has succeeded in making a symbolic victory to the Ukrainians and an embarrassing blow to the Kremlin, which had lost momentum during the war.

Rough estimates based on the size of the fireball indicate that there was a large amount of explosives in the truck, at least a few tons, depending on the type of explosive, said Nick Glumac, an engineering professor at the University of Illinois at Urbana-Champaign.

Other explosion experts have said that a smaller charge, a ton or less, may have been sufficient.

When the bomb exploded, the downward force of the blast placed enormous pressure on the bridge girders, the steel girders that support the roadway.

The blast was positioned perfectly in the center of the span, where it is most prone to flex under pressure, making the beams particularly vulnerable.

Some images of the wreckage suggest the truck blew right onto one of those girders, which may also have ripped off some of the steel.

The girders gave way and the span buckled.

But the damage was great more extensive thanhuh that point

That’s because the causeway under the bomb was a continuous structure across five of the piers, extending about 900 feet, according to engineers.

The section affected by the explosion was near the center of the highway.

When the span fell, it dragged the path towards it in both directions.

The loose ends of the road at the joints on both sides slipped off the pillars on which they were supported and fell into the water.

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