All buildings are different.

Not ALL buildings have a "critical support column".

The WTC 1 & 2 towers for instance had a very symmetrical construction where the loads were fairly equally distributed, about half to the core and half to the exterior columns. The loads on the exterior columns were not exactly the same, but in general varied more by floor than within a floor. The core columns had larger columns in the outer layer, with the largest being the exterior corner columns, but still the loads were fairly evenly distributed across a lot of columns.

But then the flying BOMBS hit.

I'd say that resulted in VERY VIOLENT removal of support columns.

And now the loading on the columns changed and some took on the role of critical support columns, meaning their loads increased, while indeed, the loads on other columns decreased.

It was the now asymmetrical forces that played the biggest role in the towers destruction.

The reason WTC 2 fell first was because the damage and fires were more asymmetrical than in WTC 1.

Which is why your "50% could be removed and the building still stood" is true but not relevant. 50% of the support could be removed ONLY if done in a manner such that the remaining loads were EQUALLY supported by the remaining structure.

But such was NOT the case in EITHER of the towers.


As to what took out the instant support?

Fire and Gravity.

As the fire side bowed in due to the asymmetric loads the long span of laterally unsupported exterior columns began to fail at the point of the highest loads. As the columns failed the loads they were carrying spread to adjacent columns causing them to fail.

As the side failed the interior columns exceeded their limits and also buckled.

Essentially once the bowing of one wall started the collapse had begun and simply accelerated as the loads shifted back and forth between the failing wall and the failing core.

(A better description is found in the NIST report)

As far as OKC, total bovine poo (about the second bomb), but as to the destruction of the building, clearly it suffered a progressive collapse where the truck bomb took out a key HORIZONTAL beam, but since there was no widespread fire (as in the WTC towers), once the collapse of the front center was over there was nothing to cause the collapse to spread to the rear and sides of the building.

Yes, steel is incredibly strong, but designers take advantage of that and load it up to a significant percent of its ability to withstand loads. The remaining ability is related to the temp of the steel. Designers know this and thus steel buildings are protected by sprinkler systems and the steel is fireproofed.

When you introduce a multifloor fire and let it burn but make no effort to fight the fire and the sprinkler system is not working and when much of the CRITICAL insulation is gone, and then when the loads on much of the structure are much higher than anticipated due to massive asymmetrical structural damage. Well then the strength of the steel can be exceeded.

Arthur

i know the official lie, arthur.
it's still a lie.

there is no repeatability in the 'science' put forth in the NIST report. it is an untested, unreproducible THEORY.

there is no proof fireproofing was removed.
there is no evidence suggesting the fires released enough heat to affect even unprotected steel.
fire effects are not 'instant' the way bombs are.
there is no proof of the 'inevitability' of total collapse.

the handwaving from the OCT camp is THE ONLY LEG the official story stands on.
that's a critical column that IS being gradually weakened by the minute.

[poetry]
i think there's a good possibility anthrax knocked down wtc7.
it sure as heck knocked the constitution into the ground.[/poetry]