The owner of a nearby dumpling restaurant who witnessed the collapse told Caixin there had been many large vehicles on the bridge at that time. One of them was a truck carrying six huge coils of steel, which the man, surnamed Yu, guessed had caused the bridge to fall towards that side.
According to photos from the scene, what Yu saw were hot-rolled steel coils. One of the coils had a certificate affixed to it, stating that it was manufactured by Rizhao Iron and Steel Holding Co. Ltd. and weighed 2,853 kilograms (6,290 pounds). If all six coils weighed that much the truck would have come in at 171 tons, which is considered overweight.
A bridge expert who was on the scene as part of rescue efforts said that the collapse should not have been caused by a single overloaded vehicle. The overloaded truck found at the scene had a load of about 170 tons, but the bridge should be able to withstand at least 4,500 tons of pressure, he said.
The bridge in Wuxi was a single-column pier, a common style of urban bridge where one column supports the superstructure. The expert said the bridge fractured between two piers, but further analysis was needed to determine whether the truck caused the fracture, or if it had been there prior to the incident.
Bridge and road collapses are not uncommon in China, and do often occur due to overloaded trucks. Bridge experts have previously told Caixin that many of the Chinese bridges that have collapsed in the past have actually been up to construction and design standards. Overloading of trucks and violation of traffic rules are a widespread problem in China.
The truck has a tungsten frame and weighs 150 tons empty. The tires are solid steel, painted to look like rubber. /s
Anyone watching serpentza on YouTube will see coverage of the generally shoddy construction widely available in China. Elite apartment buildings where floors sometimes just open several feet across, because the concrete was mixed to flour-dough levels of strength.
If the span was routinely operating in a high (overloaded) stress range then fatigue comes to mind. In the video you can see the span deflect and rotate as the trucks pass.
The surviving span shows an unusual support, where the flared corbel at the top of the beam doesn't actually do anything structurally, the span sits only on the top of the beam. The second picture shows that the fallen span is essentially intact, as are its supports, confirming from the video that the span essentially tipped off its supports. That doesn't appear to be a proper design. A further image shows that one of the supports has lost its little tip-top, suggesting that was the point of failure, which resulted in the span rolling inward toward the other span as its support post disintegrated
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
Perhaps too many heavy trucks in the left lane exceeded the anticipated unbalanced load over the length of the continuous span. But I mean I only see two trucks.
I’m not a bridge designer but I don’t see how torsion on the span is resisted when there’s only a single bearing centered on each column. And with the flared shape of the column you would expect to see a pair of bearings, yet I only see one in the photos.
That pier in above photo actually has two bearing points. Seems like that might have been what they were reliant on to take out the torsion if there was no end built into the abutments.
I wouldn't say its totally unusual to just have a single bearing on a box girder, especially if it's curved you can get some stabity out of it at larger curvyness and there's some means of resisting torsion forces at some of the supports. It looks pretty straight to me though.
Perhaps there is typically heavy truck traffic on this route traveling in one of the lanes exclusively. That could have caused excessive fatigue on the single bearing if it’s constantly being loaded eccentrically.
Didn't seem to be a plausible design to me. If both lanes are equally loaded at all times, that's great, but if one lane, then the other, gets loaded, the roadway will rock on its support, thereby fatiguing both any metal (not evident in any picture to date) and the concrete.
TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!
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