Giant Concrete Oil Platform "Wobbling", Is This Normal?

This is the beast before the topsides were fitted.
It cracked during construction, they just plastered over the cracks and carried on. It's called the Ninian Central Platform. I've started other threads about it.

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No wonder we are wobbling a few 16 mtr waves passing through. Always feel for the crews of the standby vessels in this weather

Off our graph scale now waves above 20mtr at times now with 9 to 10 mtr steady waves

I'm wondering how platform wobble is measured, and if it's got worse over the years? Does anyone have experience of concrete platform wobble?

a reply to: Kester

Normally "wobble" or flex is engineered into structures. I've been in tall buildings on windy days and seen the water in the toilet sloshing around.

Those charts don't show how much it is wobbling though.

a reply to: Phage

Being thick cast concrete and of short, sturdy circular cross section I can't see how flex could be designed in the same way it's designed into tall buildings.

a reply to: Kester

Didn't know if you had seen this but I thought you'd enjoy it...

a reply to: Kester
Bearing surfaces. Articulated joints.

But if someone designed a seaborne platform for the North Sea to be completely rigid, it was a bad idea. Because the ocean is somewhat of an irresistible force.

a reply to: twitchy

Thanks, actually I'm the YouTuber who posted those videos. This is a short one that gets to the point.

a reply to: Kester

I don't get much of a point. And even less information.

a reply to: Phage

It's possible the cyclic forces have over time changed conditions under the platform and the whole thing is rocking rather than flex in the structure.

The holes in the top part of the outer wall allow water through, easing the wave force.
"A 14 m wide central shaft is surrounded by a breakwater wall ("Jarlin Wall") 45 m in diameter and 1.6 m thick pierced with 15m diameter holes." www.writeopinions.com...

originally posted by: Kester
This is the beast before the topsides were fitted.

It cracked during construction, they just plastered over the cracks and carried on. It's called the Ninian Central Platform. I've started other threads about it.

www.facebook.com...

No wonder we are wobbling a few 16 mtr waves passing through. Always feel for the crews of the standby vessels in this weather

Off our graph scale now waves above 20mtr at times now with 9 to 10 mtr steady waves

I'm wondering how platform wobble is measured, and if it's got worse over the years? Does anyone have experience of concrete platform wobble?

I'm not an expert on concrete but when it cracks, how serious it is, generally depends on the depth and the length of the crack and the reason it cracked.

I worked in the Transamerica building, I guess it's the AT&T center now.

It's built on rollers, and the lights are hung on hinges --- something I can attest to --- as they swing during an earthquake.

a reply to: Azureblue

They are enormous vertical cracks I think in the inside of the lower part of outer wall. I saw photographs of the cracks briefly in 1979, it's a struggle to remember exactly what I was shown. I think the reason was pouring the concrete too fast and the resulting heat during curing.

I'm wondering are the cracks getting worse and the platform is slowly disintegrating? Has the platform always wobbled in heavy seas to the extent it does now? Or is the whole structure rocking on an unevenly compressed seabed?

a reply to: Annee

The WTC towers had big rubber blocks to dampen the movement. But this oil platform is essentially one lump of concrete sitting on the seabed. The proportions are very different from a tower block, like a short tree stump on a huge root rather than a tree trunk. Given the materials and the proportions I have difficulty imagining much in the way of flex. The big question is has it always wobbled to this extent or is it getting worse? The amount of money resting on that question is bound to affect the ease with which we get an answer.

originally posted by: Kester
a reply to: Azureblue

They are enormous vertical cracks I think in the inside of the lower part of outer wall. I saw photographs of the cracks briefly in 1979, it's a struggle to remember exactly what I was shown. I think the reason was pouring the concrete too fast and the resulting heat during curing.

I'm wondering are the cracks getting worse and the platform is slowly disintegrating? Has the platform always wobbled in heavy seas to the extent it does now? Or is the whole structure rocking on an unevenly compressed seabed?

Could be any or a combo of all but it certainly don't sound too good.

While I suppose it wasn't done on the construction of this platform, good quality control requires a slump test to be performed and also a crush test performed on a sample and test piece, taken from each batch of concrete.

This should come out in an investigation and inquest as something that either something that was done or was not done if something terrible happens.

originally posted by: Kester
a reply to: Annee

The WTC towers had big rubber blocks to dampen the movement. But this oil platform is essentially one lump of concrete sitting on the seabed. The proportions are very different from a tower block, like a short tree stump on a huge root rather than a tree trunk. Given the materials and the proportions I have difficulty imagining much in the way of flex. The big question is has it always wobbled to this extent or is it getting worse? The amount of money resting on that question is bound to affect the ease with which we get an answer.

Not something I want to be on.

Doesn't sound good.

a reply to: Annee

They don't sleep when it's rough.

a reply to: Azureblue

I had a message from someone whose father tested concrete batches on the Ninian. I'm sure he did his best, but I have heard of concrete testers, and others, being told to ignore bad results and approve dodgy batches.

The Ninian has stressed cables running around it. The grout pumped into the voids around these cables was found not to have fully filled the voids. I guess the vertical cracks have allowed seawater to enter many of these channels and corrode sections of cable.

If something terrible happens everyone will realise, as with the WTC towers, the essential paperwork needed for the investigation went missing shortly after construction was completed.

They knew.

It's so close to shore, why didn't they just put it on shore? I suppose on shore you would be able to see the pollution instead of it filtering slowly into the water unnoticed.

a reply to: rickymouse

No, it was floated far out to sea. It's sitting on the seabed with a maze of pipelines around it.